Group,
Maybe someone can help with the following problem on my 72 Z600. It
runs fine at idle, runs fine to redline, any throttle position
through all gears except - on the highway, once I get to 60 or 65 it
will hold that speed, but "bucks" rather severely when I try to
accelerate (the whole car jerks back and forth and slows down). As
long as I keep the throttle steady its fine - as soon
as I give it a little more throttle to accelerate is when it
misbehaves. The car "bucks" and slows down until I let off the
accelerator.
Some history - relatively low mile car, checked points and timing to
best of my ability, carb was disassembled and cleaned, new jets
installed, and I've tried both settings on the accelerator pump rod
and it made no difference. However, the gap on the accelerator pump
seems wide based on the factory manual (.018" is what I remember). My
best guess its fuel somehow, but have run out of ideas.
Thanks for any help you can provide
Ray
Carb problem?
Re: Carb problem
The accelerator pump doesn't do anything at all past a stopped
acceleration. The carb piston could be stuck or spring missing? Float
level is very important, bowl should be 3/4 full when you drop the
bowl keeping the carb vertical. Actually it sounds like water
contamination. Check fuel filter - it's under the back seat on a
coupe, you can renew it with an early model Civic filter.
Miles
acceleration. The carb piston could be stuck or spring missing? Float
level is very important, bowl should be 3/4 full when you drop the
bowl keeping the carb vertical. Actually it sounds like water
contamination. Check fuel filter - it's under the back seat on a
coupe, you can renew it with an early model Civic filter.
Miles
-
dealadayray
- Posts: 1
- Joined: Sun Aug 18, 2002 12:08 am
Re: Carb problem?
Well Ray;
It sounds like any of the following:
Carb adjusted to lean or to rich.
Vacuum line to advancer leaking
Obstructed fuel line
Bad plugs - or wrong heat range
Plug wires - or ends are not tight - If your using original plug wire ends
check to see if the wire inside (the one that holds the plug upper threads)
is used to hold in place might not be holding them all.
Rich carb fouling spark
Point breaker plate has slop - which is allowing the points to reach their
highest rpm level sooner than a tight (no slop) breaker plate will give.
Rocker arms have a flat spot - Causing a timing slump at speed
Cam teeth are becoming low in the grooves between the teeth - causing the
engine to be out of time before 6K rpm's.
Poor Ground
Weak Coil
Excessive carbon in cylinders
Valves sticking
Broken inner valve spring
Fuel Pump not holding consistently.
Vent hole in fuel tank cap not open and venting.
I know this is a lot of things to look at, but some like plugs and grounds
show up during idling speeds too. Normally a well tuned Honda 600 engine
will rev to rpm levels of 7.5K before dropping off. Unless you are using
CB100 points, then the acceleration arc becomes lower.
Bill
It sounds like any of the following:
Carb adjusted to lean or to rich.
Vacuum line to advancer leaking
Obstructed fuel line
Bad plugs - or wrong heat range
Plug wires - or ends are not tight - If your using original plug wire ends
check to see if the wire inside (the one that holds the plug upper threads)
is used to hold in place might not be holding them all.
Rich carb fouling spark
Point breaker plate has slop - which is allowing the points to reach their
highest rpm level sooner than a tight (no slop) breaker plate will give.
Rocker arms have a flat spot - Causing a timing slump at speed
Cam teeth are becoming low in the grooves between the teeth - causing the
engine to be out of time before 6K rpm's.
Poor Ground
Weak Coil
Excessive carbon in cylinders
Valves sticking
Broken inner valve spring
Fuel Pump not holding consistently.
Vent hole in fuel tank cap not open and venting.
I know this is a lot of things to look at, but some like plugs and grounds
show up during idling speeds too. Normally a well tuned Honda 600 engine
will rev to rpm levels of 7.5K before dropping off. Unless you are using
CB100 points, then the acceleration arc becomes lower.
Bill
-
kuranhonda
- Posts: 6
- Joined: Thu Sep 03, 2009 10:34 pm
Re: Carb problem
Thanks to both replies. I'm going to try the easy stuff first - new
fuel filter, re-check the plugs and timing, then go through the carb
again...and hope one of these is the problem so I don't have to do
some of the hard stuff.
Miles and Bill - thanks again for the help. I'll let you know what it
turns out to be.
Ray
fuel filter, re-check the plugs and timing, then go through the carb
again...and hope one of these is the problem so I don't have to do
some of the hard stuff.
Miles and Bill - thanks again for the help. I'll let you know what it
turns out to be.
Ray
Carb problem?
A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
Thanks in advance
Ray
This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
Thanks in advance
Ray
-
lyletrudell
- Posts: 56
- Joined: Wed Apr 14, 2010 12:54 pm
Re: Carb problem?
Original owner, with 34K that is great!
900 miles a year!
So lots of sitting and time for rust and old fuel to gum everything up. A carb rebuild 8 years ago! The O-rings could be bad and passages plugged after that time, plus all rebuilds are not the same.
So it stalls/bucks under high rpm and load, this is when it uses the most fuel.
Could be many things but it sounds fuel related, start simple, I would guess:
*Old or bad gas, car sits for long periods.
*Fuel flow problems, rust plugged lines, filters, screens....
*Float level too low.
*Worn/old Fuel pump, pressure too low.
*Wrong float needle or sticking needle.
*Accelerator pump working?
*O-rings dried out after 8 years
*Vacuum leaks.
It runs good at partial throttle so it's not anything major, look at secondary jet and needle also.
Good luck.
Lyle
900 miles a year!
So lots of sitting and time for rust and old fuel to gum everything up. A carb rebuild 8 years ago! The O-rings could be bad and passages plugged after that time, plus all rebuilds are not the same.
So it stalls/bucks under high rpm and load, this is when it uses the most fuel.
Could be many things but it sounds fuel related, start simple, I would guess:
*Old or bad gas, car sits for long periods.
*Fuel flow problems, rust plugged lines, filters, screens....
*Float level too low.
*Worn/old Fuel pump, pressure too low.
*Wrong float needle or sticking needle.
*Accelerator pump working?
*O-rings dried out after 8 years
*Vacuum leaks.
It runs good at partial throttle so it's not anything major, look at secondary jet and needle also.
Good luck.
Lyle
--- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
> This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
> I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
> Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
> On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
> Thanks in advance
> Ray
Re: Carb problem?
I noticed that my description was a little misleading in the history of the car. The car sat for 20 years - from the late 70's until the late 90's. Then I "restored" it - new paint, new bumper, exhaust system, shocks - and drained the fuel, cleaned the tank, cleaned and rebuilt the carb, put in a new fuel filter. Since then the car has been driven every year - not a lot, but running errands around town, going to local shows, etc. I probably run a tank of gas through a year, maybe less. Don't know if that matters, but I can see where my history was misleading on the storage time and when the rebuild was done. In the last 8 years or so it was seldom driven on highways where 60 mph was legal, so I'm not sure if the problem has been there ever since the restoration, or just showed up last fall when I first noticed it.
--- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
> This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
> I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
> Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
> On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
> Thanks in advance
> Ray
Re: Carb problem - thanks
Lyle,
Thanks for the tips. I am going to start by double checking the fuel filter, and then going through the carb again as you pretty much confirmed that it almost has to be a fuel problem - and my guess is carb somehow.
Ray
Thanks for the tips. I am going to start by double checking the fuel filter, and then going through the carb again as you pretty much confirmed that it almost has to be a fuel problem - and my guess is carb somehow.
Ray
--- In
2cylinderhondas@yahoogroups.com
, "lyletrudell" wrote:
> Original owner, with 34K that is great!
> 900 miles a year!
> So lots of sitting and time for rust and old fuel to gum everything up. A carb rebuild 8 years ago! The O-rings could be bad and passages plugged after that time, plus all rebuilds are not the same.
> So it stalls/bucks under high rpm and load, this is when it uses the most fuel.
> Could be many things but it sounds fuel related, start simple, I would guess:
> *Old or bad gas, car sits for long periods.
> *Fuel flow problems, rust plugged lines, filters, screens....
> *Float level too low.
> *Worn/old Fuel pump, pressure too low.
> *Wrong float needle or sticking needle.
> *Accelerator pump working?
> *O-rings dried out after 8 years
> *Vacuum leaks.
> It runs good at partial throttle so it's not anything major, look at secondary jet and needle also.
> Good luck.
> Lyle
> --- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> > A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
> > This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
> > I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
> > Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
> > On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
> > Thanks in advance
> > Ray
-
lyletrudell
- Posts: 56
- Joined: Wed Apr 14, 2010 12:54 pm
Re: Carb problem - thanks
Ray, a little story before we agree it's fuel.
I was tuning on my Opel GT's Weber carb about a year ago. Things were getting better with each jet change, I was thinking how good this is going and how good of a tuner I am! Then with the next jet change it ran worse, so I went back to the previous one, and it ran a little better, but not right. I kept messing with the carb until it ran like crap!
It was getting "dark" so I decided to call it quits and start again tomorrow. As I was closing the hood I noticed a spark jumping from the distributor cap, it was cracked!!!!!
New cap and and it has run great ever since.
Now, I never think it's just a fuel problem or I am a great tuner.
Check all the basic tuneup stuff first, and don't get stuck on one area!
:)
Lyle
I was tuning on my Opel GT's Weber carb about a year ago. Things were getting better with each jet change, I was thinking how good this is going and how good of a tuner I am! Then with the next jet change it ran worse, so I went back to the previous one, and it ran a little better, but not right. I kept messing with the carb until it ran like crap!
It was getting "dark" so I decided to call it quits and start again tomorrow. As I was closing the hood I noticed a spark jumping from the distributor cap, it was cracked!!!!!
New cap and and it has run great ever since.
Now, I never think it's just a fuel problem or I am a great tuner.
Check all the basic tuneup stuff first, and don't get stuck on one area!
:)
Lyle
--- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> Lyle,
> Thanks for the tips. I am going to start by double checking the fuel filter, and then going through the carb again as you pretty much confirmed that it almost has to be a fuel problem - and my guess is carb somehow.
> Ray
> --- In
2cylinderhondas@yahoogroups.com
, "lyletrudell" wrote:
> > Original owner, with 34K that is great!
> > 900 miles a year!
> > So lots of sitting and time for rust and old fuel to gum everything up. A carb rebuild 8 years ago! The O-rings could be bad and passages plugged after that time, plus all rebuilds are not the same.
> > So it stalls/bucks under high rpm and load, this is when it uses the most fuel.
> > Could be many things but it sounds fuel related, start simple, I would guess:
> > *Old or bad gas, car sits for long periods.
> > *Fuel flow problems, rust plugged lines, filters, screens....
> > *Float level too low.
> > *Worn/old Fuel pump, pressure too low.
> > *Wrong float needle or sticking needle.
> > *Accelerator pump working?
> > *O-rings dried out after 8 years
> > *Vacuum leaks.
> > It runs good at partial throttle so it's not anything major, look at secondary jet and needle also.
> > Good luck.
> > Lyle
> > --- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> > > A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
> > > This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
> > > I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
> > > Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
> > > On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan. The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tell. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com
> > > Thanks in advance
> > > Ray
Re: Carb problem?
Hi Ray,
I have been thinking about your car problem and here are my questions and suggestions;
1. What type of fuel economy do you get with the car when you are on the highway? Is it better than 36 mpg?
2. If the car (and carb) had 34,000 miles, it should not have needed a rebuild of the carb. Perhaps the o-rings may need replacing and replace the needle and seat under the float. I suspect a carb cleaning would have been sufficient to remove deposits in the carb ...... but I don't know what you saw that lead you to want to rebuild it.
I would suspect the rebuild may have introduced your problem. Here are some things to check;
a. the float level may be set wrong. The coupe service manual states the float level as 20.5 mm or 0.82 inches. The metric part is correct, the other number is wrong and should be 0.807 inches.
b. does the carb have the correct vacuum piston spring? It should be about 8 inches long and does not exert very much force.
c. a fiber washer should be present between the vacuum piston and the carb body
d. the vacuum piston has a needle jet which goes into a tube and the needle jet (one of the 2 jets you may have replaced) is on the other side. If the tube and needle were not replaced, it is possible the tube is partially clogged. It has a several small holes in it.
e. do the o-rings on each of the 2 jets give a snug fit?
f. does the cap which is between the 2 jets have a snug fit?
g. what is the condition of the carb's passageway? Pull off the piston cap (held in place with 2 screws), and remove the vacuum piston. Look down toward the jets and the venturi passageway. Is it smooth (good)? Does it show pitting (bad)?
3. While the problem does seem to be related to the carb, if I had a car with your problem, I would swap out the carb with a known good one and see if the problem goes away or if the problem still exists.
Since your problem occurs when the car is at 4500 rpm and in 4th gear when the engine is being placed under a higher load, it is possible you have a problem in the ignition or timing.
a. since the problem occurs when the engine is being placed under additional load, this requires the spark plug to fire at a higher voltage. You could have a problem with a spark plug wire experiencing arcing to the chassis.
b. the springs responsible for the mechanical advance may have weakened and the mechanical advance of the ignition timing may have the wrong profile. You can check this with a timing light. Refer to the sedan shop manual and it gives the ignition advance vs engine rpm.
With the car sitting in your driveway and the transmission in neutral, you can increase the engine rpms and take a reading with your timing light. A dial back to zero timing light is the easy way. Otherwise, you will need to put timing marks on your pulley which is adjacent to the "F" and "T" timing marks.
c. is the camshaft timed properly to the crankshaft? When the notch on the camshaft appears when the oil cap is off, the crank should be at TDC (the "T" mark).
I suspect your bucking problem may be the result of several things which are not quite correct with your car.
good luck,
Dale
A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan.
The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tel l. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com Thanks in advance Ray
I have been thinking about your car problem and here are my questions and suggestions;
1. What type of fuel economy do you get with the car when you are on the highway? Is it better than 36 mpg?
2. If the car (and carb) had 34,000 miles, it should not have needed a rebuild of the carb. Perhaps the o-rings may need replacing and replace the needle and seat under the float. I suspect a carb cleaning would have been sufficient to remove deposits in the carb ...... but I don't know what you saw that lead you to want to rebuild it.
I would suspect the rebuild may have introduced your problem. Here are some things to check;
a. the float level may be set wrong. The coupe service manual states the float level as 20.5 mm or 0.82 inches. The metric part is correct, the other number is wrong and should be 0.807 inches.
b. does the carb have the correct vacuum piston spring? It should be about 8 inches long and does not exert very much force.
c. a fiber washer should be present between the vacuum piston and the carb body
d. the vacuum piston has a needle jet which goes into a tube and the needle jet (one of the 2 jets you may have replaced) is on the other side. If the tube and needle were not replaced, it is possible the tube is partially clogged. It has a several small holes in it.
e. do the o-rings on each of the 2 jets give a snug fit?
f. does the cap which is between the 2 jets have a snug fit?
g. what is the condition of the carb's passageway? Pull off the piston cap (held in place with 2 screws), and remove the vacuum piston. Look down toward the jets and the venturi passageway. Is it smooth (good)? Does it show pitting (bad)?
3. While the problem does seem to be related to the carb, if I had a car with your problem, I would swap out the carb with a known good one and see if the problem goes away or if the problem still exists.
Since your problem occurs when the car is at 4500 rpm and in 4th gear when the engine is being placed under a higher load, it is possible you have a problem in the ignition or timing.
a. since the problem occurs when the engine is being placed under additional load, this requires the spark plug to fire at a higher voltage. You could have a problem with a spark plug wire experiencing arcing to the chassis.
b. the springs responsible for the mechanical advance may have weakened and the mechanical advance of the ignition timing may have the wrong profile. You can check this with a timing light. Refer to the sedan shop manual and it gives the ignition advance vs engine rpm.
With the car sitting in your driveway and the transmission in neutral, you can increase the engine rpms and take a reading with your timing light. A dial back to zero timing light is the easy way. Otherwise, you will need to put timing marks on your pulley which is adjacent to the "F" and "T" timing marks.
c. is the camshaft timed properly to the crankshaft? When the notch on the camshaft appears when the oil cap is off, the crank should be at TDC (the "T" mark).
I suspect your bucking problem may be the result of several things which are not quite correct with your car.
good luck,
Dale
A little background and the symptoms. I'm the original owner of a 72 Z600 and the car has 34,000 miles. It hadn't been driven for years and after tearing down the carb, cleaning everything and putting in new jets and also replacing the fuel filter about 8 years ago, everything seemed fine driving around town and going to local shows etc - until I took it on the interstate and encountered a slight grade. At about 60 miles per hour, 4500 RPM, if there is even a slight grade and I apply a little more throttle to maintain speed, the car starts "bucking", jerking back and forth. and it gets much worse, almost violent with more throttle. If I back off on the throttle just a little the engine smooths out, and it seems fine going uphill at lower speeds - I can floor it at 45 going uphill and its fine. Just last week I had a long time Honda motorcycle mechanic tune up the car - new points, new plugs, timed it, adjusted the valves, and cleaned and lubed what I call the dashpot on the carb. The condenser was not replaced - didn't have a new one to give him.
This weekend I drove the car about 400 miles round trip to a Concours event and it ran much better - until it gets to about 60-65 and encounters slight hill - then any added throttle starts the bucking. I basically have to feather the throttle to keep the car just at the point where it is happy until reaching level ground. It seems to be fine at 50 - 55 mph as long as I only use enough throttle to maintian speed up the hill. I also noticed a slight hesitation on occasion when leaving off the throttle at high speed on level ground.
I can run the engine to 5000 in any gear except 4th with no problem, use full throttle in any gear with no problem, and accelerating on level ground in 4th is fine - had the car over 65 mph on level ground - no problem.
Sure seems like something in the fuel system and most likely the carb to me. It seems like a fuel flow problem, but then again a fuel flow problem doesn't compute to me - the engine should need as much fuel at full throttle in 1st, 2nd or 3rd as it does at partial throttle in 4th, and its fine in the lower gears at any rpm and any throttle opening. But then if I was a mechanical genius it would have been fixed by now. Any Ideas??
On a more pleasant note, driving the car from Clarkston MI to the Krasl Concours on the Bluff in St Joseph MI was really great. We took the scenic route on secondary roads, the weather was perfect, and it was really fun taking a lengthy road trip in the 600 coupe. Even the hills were OK once feathering the throttle up a hill became almost automatic. The show itself was first class (getting a bottle of champagne in the "goody bag" was a pleasant surprise). It was held in a wooded park on a bluff overlooking Lake Michigan.
The car was selected as one of the cars at the show for judging by kids in a special program that Hagerty Insurance sponsors to encourage the next generation of car enthusiasts, and we were invited to another concours event in Milwaukee next summer, and had the usual fun watching people pointing and grinning at the "funny little car". Most people in this part of the country have never seen one, and those who have always have a story to tel l. Had a ball. Will post a few pictures from the show on my website http://www.honda600source.com Thanks in advance Ray