When I had this "bucking" a couple of years back, it turned out to be a spark plug wire where it goes into the coil. I mechanicaly removed the old wire and epoxyed in a new one and the problem disapeared. When the spark is weak, everything seems like it is really sensitive, including the carb. Remember, the two wires are in series and any extra resistance will really effect the engine. I had an extra 10K ohms that I couldn't account for, until I finally found the problem.
Hope this helps.
Bob Freeman
Carb problem?
Re: Carb problem?
Dale,
Thanks for the very detailed suggestions - that helps a lot.
To answer a couple of your questions:
- we got 45+ mpg on the 400 mile trip last weekend
- the timing and new points were just set by a very experienced Honda motorcycle mechanic who specializes in old Hondas so I'm confident that those two items are correct. The car ran noticeably better after he worked on it, but the bucking problem was still there
- my memory of exactly what I did to the carb is fuzzy at best. I know I replaced the needle and seat under the float, cleaned it, replaced some gaskets, but beyond that I'm not sure - it was 8 years ago
- the vacuum piston spring is original, and the Honda mechanic just cleaned and lubricated the piston - it ran the same before and after
- this wouldn't be the first time my "repairs" have made an engine worse, and most of my so-called expertise is with large V8 engines
I will take the time to go thru your list soon and let you know if/when it gets fixed
Thanks again
Ray
Thanks for the very detailed suggestions - that helps a lot.
To answer a couple of your questions:
- we got 45+ mpg on the 400 mile trip last weekend
- the timing and new points were just set by a very experienced Honda motorcycle mechanic who specializes in old Hondas so I'm confident that those two items are correct. The car ran noticeably better after he worked on it, but the bucking problem was still there
- my memory of exactly what I did to the carb is fuzzy at best. I know I replaced the needle and seat under the float, cleaned it, replaced some gaskets, but beyond that I'm not sure - it was 8 years ago
- the vacuum piston spring is original, and the Honda mechanic just cleaned and lubricated the piston - it ran the same before and after
- this wouldn't be the first time my "repairs" have made an engine worse, and most of my so-called expertise is with large V8 engines
I will take the time to go thru your list soon and let you know if/when it gets fixed
Thanks again
Ray
--- In 2cylinderhondas@yahoogroups.com, goinhm@... wrote:
> 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_ (http://www.honda600source.com/)
> Thanks in advance
> Ray
Re: Carb problem?
Hi Ray,
If you are getting 45+ mpg, you can forget about most of the items on my checklist pertaining to the carb and camshaft/crank timing. Your carb sounds like it works fine ..... at least at the highway speeds which is where you experienced the bucking. And since the bucking occurs when the engine is being placed under a load, I am leaning more toward a problem in the ignition system.
What spark plug are you using and what is the gap setting?
Dale
If you are getting 45+ mpg, you can forget about most of the items on my checklist pertaining to the carb and camshaft/crank timing. Your carb sounds like it works fine ..... at least at the highway speeds which is where you experienced the bucking. And since the bucking occurs when the engine is being placed under a load, I am leaning more toward a problem in the ignition system.
What spark plug are you using and what is the gap setting?
Dale
> Thanks
> for the very detailed suggestions - that helps a lot.
> To answer a
> couple of your questions:
> - we got 45+ mpg on the 400 mile trip last
> weekend
> - the timing and new points were just set by a very experienced > Honda motorcycle mechanic who specializes in old Hondas so I'm confident that > those two items are correct. The car ran noticeably better after he worked on > it, but the bucking problem was still there > - my memory of exactly what I > did to the carb is fuzzy at best. I know I replaced the needle and seat under > the float, cleaned it, replaced some gaskets, but beyond that I'm not sure - > it was 8 years ago > - the vacuum piston spring is original, and the Honda > mechanic just cleaned and lubricated the piston - it ran the same before and > after > - this wouldn't be the first time my "repairs" have made an engine > worse, and most of my so-called expertise is with large V8 engines > I > will take the time to go thru your list soon and let you know if/when it gets > fixed > Thanks > again > Ray
-
lyletrudell
- Posts: 56
- Joined: Wed Apr 14, 2010 12:54 pm
Re: Carb problem?
Dale's probably right.
From the new info, your car sounds like it is tuned and running almost perfect!
A miss (Bucking) at high rpm's and high load could be something as simple as a bad plug. Sometimes you get a plug that is fouled slightly or just bad and it will not fire properly under high pressure. Just replace them and keep the others as backup.
Do a basic tuneup.
I think you said you didn't replace the condensor, do that.
New wires and boots.
Coil could also be going.
Buy new parts and keep the good old ones for your backup travel kit!
My Opel-GT has a box of parts in the back......
Lyle
From the new info, your car sounds like it is tuned and running almost perfect!
A miss (Bucking) at high rpm's and high load could be something as simple as a bad plug. Sometimes you get a plug that is fouled slightly or just bad and it will not fire properly under high pressure. Just replace them and keep the others as backup.
Do a basic tuneup.
I think you said you didn't replace the condensor, do that.
New wires and boots.
Coil could also be going.
Buy new parts and keep the good old ones for your backup travel kit!
My Opel-GT has a box of parts in the back......
Lyle
--- In
2cylinderhondas@yahoogroups.com
, goinhm@... wrote:
> Hi Ray,
> If you are getting 45+ mpg, you can forget about most of the items on
> my checklist pertaining to the carb and camshaft/crank timing. Your carb
> sounds like it works fine ..... at least at the highway speeds which is
> where you experienced the bucking. And since the bucking occurs when the
> engine is being placed under a load, I am leaning more toward a problem in the
> ignition system.
> What spark plug are you using and what is the gap setting?
> Dale
> Thanks for the very detailed suggestions - that helps a lot.
> To answer a couple of your questions:
> - we got 45+ mpg on the 400 mile trip last weekend
> - the timing and new points were just set by a very experienced Honda
> motorcycle mechanic who specializes in old Hondas so I'm confident that those
> two items are correct. The car ran noticeably better after he worked on it,
> but the bucking problem was still there
> - my memory of exactly what I did to the carb is fuzzy at best. I know I
> replaced the needle and seat under the float, cleaned it, replaced some
> gaskets, but beyond that I'm not sure - it was 8 years ago
> - the vacuum piston spring is original, and the Honda mechanic just
> cleaned and lubricated the piston - it ran the same before and after
> - this wouldn't be the first time my "repairs" have made an engine worse,
> and most of my so-called expertise is with large V8 engines
> I will take the time to go thru your list soon and let you know if/when it
> gets fixed
> Thanks again
> Ray
Re: Carb problem?
Since you are getting 46 mpg, your present tuneup is perfect.
And the 46 mpg is proof the condensor is fine. Here are some ideas;
1) where the ignition coil bolts to the chassis, you should have a ground wire going from the ignition coil frame to the engine. The original equipment was a ground strap which went from the negative terminal of the battery to the ignition coil frame and then on to the engine.
2) replacing the spark plugs is an inexpensive check and if it doesn't work, you have 2 plugs you will use someday.
3) check the spark plug wires for cracking. where the wires are held to the metal chassis by tabs, look for wear/cracking.
4) check the connectors on the end of the plug wires ..... sometimes they are not making contact to the plug wires and the car works because the spark is able to jump across the gap. Under higher engine load, the coil cannot put out enough voltage to jump this gap plus the spark plug gap. Instead, the coil arcs over somewhere else ...... perhaps inside the coil.
5) the sedan shop manual describes how to test the coil by measuring the gap the spark will jump. I use a Lisle Ignition Spark Tester (p/n 50850) which connects to the spark plug connector and lets you vary the gap. I paid less than $5 for it. you can crank over the engine and see how much spark gap you can get from the coil...... no need for the special machine described in the shop manual.
6) the insulator of the spark plug should be clean and any boot going over the plug should also be clean to minimize high voltage leakage.
7) the condensor supplied by Honda for these cars is very durable. I have used ones dating back to 1970 which test out to the same values for capacitance and dissipation factor as a new, unused one.
good luck,
Dale
And the 46 mpg is proof the condensor is fine. Here are some ideas;
1) where the ignition coil bolts to the chassis, you should have a ground wire going from the ignition coil frame to the engine. The original equipment was a ground strap which went from the negative terminal of the battery to the ignition coil frame and then on to the engine.
2) replacing the spark plugs is an inexpensive check and if it doesn't work, you have 2 plugs you will use someday.
3) check the spark plug wires for cracking. where the wires are held to the metal chassis by tabs, look for wear/cracking.
4) check the connectors on the end of the plug wires ..... sometimes they are not making contact to the plug wires and the car works because the spark is able to jump across the gap. Under higher engine load, the coil cannot put out enough voltage to jump this gap plus the spark plug gap. Instead, the coil arcs over somewhere else ...... perhaps inside the coil.
5) the sedan shop manual describes how to test the coil by measuring the gap the spark will jump. I use a Lisle Ignition Spark Tester (p/n 50850) which connects to the spark plug connector and lets you vary the gap. I paid less than $5 for it. you can crank over the engine and see how much spark gap you can get from the coil...... no need for the special machine described in the shop manual.
6) the insulator of the spark plug should be clean and any boot going over the plug should also be clean to minimize high voltage leakage.
7) the condensor supplied by Honda for these cars is very durable. I have used ones dating back to 1970 which test out to the same values for capacitance and dissipation factor as a new, unused one.
good luck,
Dale
> From the
> new info, your car sounds like it is tuned and running almost perfect!
> A
> miss (Bucking) at high rpm's and high load could be something as simple as a > bad plug. Sometimes you get a plug that is fouled slightly or just bad and it > will not fire properly under high pressure. Just replace them and keep the > others as backup.
> Do a basic tuneup.
> I think you said you didn't replace
> the condensor, do that.
> New wires and boots.
> Coil could also be
> going.
> Buy new parts and keep the good old ones for your backup travel > kit!
> My Opel-GT has a box of parts in the back......
> Lyle
> --- In
> 2cylinderhondas@yahoogroups.com
> ,
> goinhm@... wrote:
> > Hi Ray,
> > If you are getting
> 45+ mpg, you can forget about most of the items on
> > my checklist
> pertaining to the carb and camshaft/crank timing. Your carb > > sounds > like it works fine ..... at least at the highway speeds which is
> where you experienced the bucking. And since the bucking occurs when the
> > engine is being placed under a load, I am leaning more toward a > problem in the > > ignition system.
> > What spark plug are
> you using and what is the gap setting?
> > Dale
> Thanks for the very detailed suggestions - that helps a lot.
> To answer a couple of your questions:
> > - we got 45+ mpg on the 400 mile
> trip last weekend
> > - the timing and new points were just set by a very
> experienced Honda
> > motorcycle mechanic who specializes in old Hondas
> so I'm confident that those
> > two items are correct. The car ran
> noticeably better after he worked on it,
> > but the bucking problem was
> still there
> > - my memory of exactly what I did to the carb is fuzzy at > best. I know I > > replaced the needle and seat under the float, cleaned > it, replaced some > > gaskets, but beyond that I'm not sure - it was 8 > years ago > > - the vacuum piston spring is original, and the Honda > mechanic just > > cleaned and lubricated the piston - it ran the same > before and after > > - this wouldn't be the first time my "repairs" have > made an engine worse, > > and most of my so-called expertise is with > large V8 engines
> > I will take the time to go thru your list
> soon and let you know if/when it
> > gets fixed
> > Thanks
> again
> > Ray
Re: Carb problem?
Lyle,
Thanks for your continued help. See my other reply for the deatils, but it wasn't plugs or bad ground - will look for replacement wires and boots next.
Ray
Thanks for your continued help. See my other reply for the deatils, but it wasn't plugs or bad ground - will look for replacement wires and boots next.
Ray
--- In
2cylinderhondas@yahoogroups.com
, "lyletrudell" wrote:
> Dale's probably right.
> From the new info, your car sounds like it is tuned and running almost perfect!
> A miss (Bucking) at high rpm's and high load could be something as simple as a bad plug. Sometimes you get a plug that is fouled slightly or just bad and it will not fire properly under high pressure. Just replace them and keep the others as backup.
> Do a basic tuneup.
> I think you said you didn't replace the condensor, do that.
> New wires and boots.
> Coil could also be going.
> Buy new parts and keep the good old ones for your backup travel kit!
> My Opel-GT has a box of parts in the back......
> Lyle
> --- In
2cylinderhondas@yahoogroups.com
, goinhm@ wrote:
> > Hi Ray,
> > If you are getting 45+ mpg, you can forget about most of the items on
> > my checklist pertaining to the carb and camshaft/crank timing. Your carb
> > sounds like it works fine ..... at least at the highway speeds which is
> > where you experienced the bucking. And since the bucking occurs when the
> > engine is being placed under a load, I am leaning more toward a problem in the
> > ignition system.
> > What spark plug are you using and what is the gap setting?
> > Dale
> > Thanks for the very detailed suggestions - that helps a lot.
> > To answer a couple of your questions:
> > - we got 45+ mpg on the 400 mile trip last weekend
> > - the timing and new points were just set by a very experienced Honda
> > motorcycle mechanic who specializes in old Hondas so I'm confident that those
> > two items are correct. The car ran noticeably better after he worked on it,
> > but the bucking problem was still there
> > - my memory of exactly what I did to the carb is fuzzy at best. I know I
> > replaced the needle and seat under the float, cleaned it, replaced some
> > gaskets, but beyond that I'm not sure - it was 8 years ago
> > - the vacuum piston spring is original, and the Honda mechanic just
> > cleaned and lubricated the piston - it ran the same before and after
> > - this wouldn't be the first time my "repairs" have made an engine worse,
> > and most of my so-called expertise is with large V8 engines
> > I will take the time to go thru your list soon and let you know if/when it
> > gets fixed
> > Thanks again
> > Ray
Re: Carb problem?
Dale,
1.The plugs were Bosch platinum WR7DP gapped at .028 and they looked fine (not many miles over the last 8 years), but I put in new NGK BPR6ES plugs gapped the same - made no difference.
2. Ground wire is factory original just as you described, plug wires and connectors don't show any obvious issues. Can you buy replacements or is this a fabricate your own proposition? The coil end on the wires looks to be unique to the Honda - don't look anything like my early Firebird V8 wires.
3. I am going to find the Lisle tester - sounds like something I need in my toolkit anyway. Is it possible to have too many tools??
4. One more symptom - pushed in the clutch when the engine was "bucking" and gave it more throttle - the engine was temporarily (a couple seconds or so) almost dead - did not respond to the throttle even with the clutch disengaged. I have not checked the float level in the carb and am going to do that after exhausting the obvious electrical possibilities.
Thanks again for your continued help.
Ray
1.The plugs were Bosch platinum WR7DP gapped at .028 and they looked fine (not many miles over the last 8 years), but I put in new NGK BPR6ES plugs gapped the same - made no difference.
2. Ground wire is factory original just as you described, plug wires and connectors don't show any obvious issues. Can you buy replacements or is this a fabricate your own proposition? The coil end on the wires looks to be unique to the Honda - don't look anything like my early Firebird V8 wires.
3. I am going to find the Lisle tester - sounds like something I need in my toolkit anyway. Is it possible to have too many tools??
4. One more symptom - pushed in the clutch when the engine was "bucking" and gave it more throttle - the engine was temporarily (a couple seconds or so) almost dead - did not respond to the throttle even with the clutch disengaged. I have not checked the float level in the carb and am going to do that after exhausting the obvious electrical possibilities.
Thanks again for your continued help.
Ray
--- In
2cylinderhondas@yahoogroups.com
, goinhm@... wrote:
> Since you are getting 46 mpg, your present tuneup is perfect. And the 46
> mpg is proof the condensor is fine. Here are some ideas;
> 1) where the ignition coil bolts to the chassis, you should have a
> ground wire going from the ignition coil frame to the engine. The original
> equipment was a ground strap which went from the negative terminal of the
> battery to the ignition coil frame and then on to the engine.
> 2) replacing the spark plugs is an inexpensive check and if it doesn't
> work, you have 2 plugs you will use someday.
> 3) check the spark plug wires for cracking. where the wires are held to
> the metal chassis by tabs, look for wear/cracking.
> 4) check the connectors on the end of the plug wires ..... sometimes they
> are not making contact to the plug wires and the car works because the
> spark is able to jump across the gap. Under higher engine load, the coil
> cannot put out enough voltage to jump this gap plus the spark plug gap.
> Instead, the coil arcs over somewhere else ...... perhaps inside the coil.
> 5) the sedan shop manual describes how to test the coil by measuring the
> gap the spark will jump. I use a Lisle Ignition Spark Tester (p/n 50850)
> which connects to the spark plug connector and lets you vary the gap. I
> paid less than $5 for it. you can crank over the engine and see how much
> spark gap you can get from the coil...... no need for the special machine
> described in the shop manual.
> 6) the insulator of the spark plug should be clean and any boot going over
> the plug should also be clean to minimize high voltage leakage.
> 7) the condensor supplied by Honda for these cars is very durable. I
> have used ones dating back to 1970 which test out to the same values for
> capacitance and dissipation factor as a new, unused one.
> good luck,
> Dale
> From the new info, your car sounds like it is tuned and running almost
> perfect!
> A miss (Bucking) at high rpm's and high load could be something as simple
> as a bad plug. Sometimes you get a plug that is fouled slightly or just bad
> and it will not fire properly under high pressure. Just replace them and
> keep the others as backup.
> Do a basic tuneup.
> I think you said you didn't replace the condensor, do that.
> New wires and boots.
> Coil could also be going.
> Buy new parts and keep the good old ones for your backup travel kit!
> My Opel-GT has a box of parts in the back......
> Lyle
> --- In
_2cylinderhondas@yahoogroups.com
_
> (mailto:
2cylinderhondas@yahoogroups.com
) , goinhm@ wrote:
> > Hi Ray,
> > If you are getting 45+ mpg, you can forget about most of the items on
> > my checklist pertaining to the carb and camshaft/crank timing. Your carb
> > sounds like it works fine ..... at least at the highway speeds which is
> > where you experienced the bucking. And since the bucking occurs when the
> > engine is being placed under a load, I am leaning more toward a problem
> in the
> > ignition system.
> > What spark plug are you using and what is the gap setting?
> > Dale
> > Thanks for the very detailed suggestions - that helps a lot.
> > To answer a couple of your questions:
> > - we got 45+ mpg on the 400 mile trip last weekend
> > - the timing and new points were just set by a very experienced Honda
> > motorcycle mechanic who specializes in old Hondas so I'm confident that
> those
> > two items are correct. The car ran noticeably better after he worked on
> it,
> > but the bucking problem was still there
> > - my memory of exactly what I did to the carb is fuzzy at best. I know I
> > replaced the needle and seat under the float, cleaned it, replaced some
> > gaskets, but beyond that I'm not sure - it was 8 years ago
> > - the vacuum piston spring is original, and the Honda mechanic just
> > cleaned and lubricated the piston - it ran the same before and after
> > - this wouldn't be the first time my "repairs" have made an engine
> worse,
> > and most of my so-called expertise is with large V8 engines
> > I will take the time to go thru your list soon and let you know if/when
> it
> > gets fixed
> > Thanks again
> > Ray
Re: Carb problem?
Hi Ray,
See my comments below.
See my comments below.
> 1.The
> plugs were Bosch platinum WR7DP gapped at .028 and they looked fine (not many > miles over the last 8 years), but I put in new NGK BPR6ES plugs gapped the > same - made no difference.
I see the NGK site is recommending the BPR6ES as the replacement for the B8ES plug. The gap which NGK recommends is 0.032 inches.
> 2.
> Ground wire is factory original just as you described, plug wires and > connectors don't show any obvious issues. Can you buy replacements or is this > a fabricate your own proposition? The coil end on the wires looks to be unique > to the Honda - don't look anything like my early Firebird V8 > wires.
I don't know of anything which is available and I have had to fabricate it myself. Others on this newsgroup may have found a coil and wire combination which works. Bill Colford has an article on the yahoo site about replacing the spark plug wires to the coil.
> 3.
> I am going to find the Lisle tester - sounds like something I need in my > toolkit anyway. Is it possible to have too many tools??
Click
here
to see the tester. the website is
www.lislecorp.com
> 4.
> One more symptom - pushed in the clutch when the engine was "bucking" and gave > it more throttle - the engine was temporarily (a couple seconds or so) almost > dead - did not respond to the throttle even with the clutch disengaged. I have > not checked the float level in the carb and am going to do that after > exhausting the obvious electrical possibilities.
This new clue points me toward the fuel supply and the ignition.
Since the problem only appears for a couple of seconds and then self-corrects, it sounds like an electrical issue. Possibly;
a) the fuel pump's response is lagging when more fuel is being required causing the float level to drop momentarily....this could lead to your engine appearing to die for a couple seconds.
The fuel line could also be partially obstructed.
You could disconnect the fuel line at the carb, and measure the delivery rate into a container when power is applied to the fuel pump. The shop manual shows 250 cc per minute ...... about 8 oz every minute.
b) the coil (or the plug wires/connectors) are the problem
c) then there are some bizarre scenarios I could come up with but they would not fit the pattern of a car which runs perfect except under a certain set of sequences.
Regarding checking the float level.... since you are
getting 46 mpg, the float level should be fine. Now that I have made that statement, there is a small fuel filter under the needle and seat. If it is partially clogged, it could be presenting the obstruction which slows the fuel delivery.
I think we will all be interested in knowing what solves your problem.
good luck,
Dale
-
lyletrudell
- Posts: 56
- Joined: Wed Apr 14, 2010 12:54 pm
Re: Carb problem?
Hi Ray, your a mechanical guy, which makes it easy to help you.
Dale is clever and he know's the little tricks or problems these cars develope over time, good friend to have.
I am new to the Honda 600 cars, but I will add things I have learned from motorcycles and other cars, hey I might get lucky.
One other thing to consider is a blocked exhaust.
All the fuel and air going in is great, but if the burn't gas can't get out....
Rusted baffles in a muffler could block the flow, have seen it before.
Murphy's law.
Lyle
Dale is clever and he know's the little tricks or problems these cars develope over time, good friend to have.
I am new to the Honda 600 cars, but I will add things I have learned from motorcycles and other cars, hey I might get lucky.
One other thing to consider is a blocked exhaust.
All the fuel and air going in is great, but if the burn't gas can't get out....
Rusted baffles in a muffler could block the flow, have seen it before.
Murphy's law.
Lyle
--- In
2cylinderhondas@yahoogroups.com
, "rhamman70" wrote:
> Dale,
> 1.The plugs were Bosch platinum WR7DP gapped at .028 and they looked fine (not many miles over the last 8 years), but I put in new NGK BPR6ES plugs gapped the same - made no difference.
> 2. Ground wire is factory original just as you described, plug wires and connectors don't show any obvious issues. Can you buy replacements or is this a fabricate your own proposition? The coil end on the wires looks to be unique to the Honda - don't look anything like my early Firebird V8 wires.
> 3. I am going to find the Lisle tester - sounds like something I need in my toolkit anyway. Is it possible to have too many tools??
> 4. One more symptom - pushed in the clutch when the engine was "bucking" and gave it more throttle - the engine was temporarily (a couple seconds or so) almost dead - did not respond to the throttle even with the clutch disengaged. I have not checked the float level in the carb and am going to do that after exhausting the obvious electrical possibilities.
> Thanks again for your continued help.
> Ray
> --- In
2cylinderhondas@yahoogroups.com
, goinhm@ wrote:
> > Since you are getting 46 mpg, your present tuneup is perfect. And the 46
> > mpg is proof the condensor is fine. Here are some ideas;
> > 1) where the ignition coil bolts to the chassis, you should have a
> > ground wire going from the ignition coil frame to the engine. The original
> > equipment was a ground strap which went from the negative terminal of the
> > battery to the ignition coil frame and then on to the engine.
> > 2) replacing the spark plugs is an inexpensive check and if it doesn't
> > work, you have 2 plugs you will use someday.
> > 3) check the spark plug wires for cracking. where the wires are held to
> > the metal chassis by tabs, look for wear/cracking.
> > 4) check the connectors on the end of the plug wires ..... sometimes they
> > are not making contact to the plug wires and the car works because the
> > spark is able to jump across the gap. Under higher engine load, the coil
> > cannot put out enough voltage to jump this gap plus the spark plug gap.
> > Instead, the coil arcs over somewhere else ...... perhaps inside the coil.
> > 5) the sedan shop manual describes how to test the coil by measuring the
> > gap the spark will jump. I use a Lisle Ignition Spark Tester (p/n 50850)
> > which connects to the spark plug connector and lets you vary the gap. I
> > paid less than $5 for it. you can crank over the engine and see how much
> > spark gap you can get from the coil...... no need for the special machine
> > described in the shop manual.
> > 6) the insulator of the spark plug should be clean and any boot going over
> > the plug should also be clean to minimize high voltage leakage.
> > 7) the condensor supplied by Honda for these cars is very durable. I
> > have used ones dating back to 1970 which test out to the same values for
> > capacitance and dissipation factor as a new, unused one.
> > good luck,
> > Dale
> > From the new info, your car sounds like it is tuned and running almost
> > perfect!
> > A miss (Bucking) at high rpm's and high load could be something as simple
> > as a bad plug. Sometimes you get a plug that is fouled slightly or just bad
> > and it will not fire properly under high pressure. Just replace them and
> > keep the others as backup.
> > Do a basic tuneup.
> > I think you said you didn't replace the condensor, do that.
> > New wires and boots.
> > Coil could also be going.
> > Buy new parts and keep the good old ones for your backup travel kit!
> > My Opel-GT has a box of parts in the back......
> > Lyle
> > --- In
_2cylinderhondas@yahoogroups.com
_
> > (mailto:
2cylinderhondas@yahoogroups.com
) , goinhm@ wrote:
> > > Hi Ray,
> > > If you are getting 45+ mpg, you can forget about most of the items on
> > > my checklist pertaining to the carb and camshaft/crank timing. Your carb
> > > sounds like it works fine ..... at least at the highway speeds which is
> > > where you experienced the bucking. And since the bucking occurs when the
> > > engine is being placed under a load, I am leaning more toward a problem
> > in the
> > > ignition system.
> > > What spark plug are you using and what is the gap setting?
> > > Dale
> > > Thanks for the very detailed suggestions - that helps a lot.
> > > To answer a couple of your questions:
> > > - we got 45+ mpg on the 400 mile trip last weekend
> > > - the timing and new points were just set by a very experienced Honda
> > > motorcycle mechanic who specializes in old Hondas so I'm confident that
> > those
> > > two items are correct. The car ran noticeably better after he worked on
> > it,
> > > but the bucking problem was still there
> > > - my memory of exactly what I did to the carb is fuzzy at best. I know I
> > > replaced the needle and seat under the float, cleaned it, replaced some
> > > gaskets, but beyond that I'm not sure - it was 8 years ago
> > > - the vacuum piston spring is original, and the Honda mechanic just
> > > cleaned and lubricated the piston - it ran the same before and after
> > > - this wouldn't be the first time my "repairs" have made an engine
> > worse,
> > > and most of my so-called expertise is with large V8 engines
> > > I will take the time to go thru your list soon and let you know if/when
> > it
> > > gets fixed
> > > Thanks again
> > > Ray
Re: Carb problem?
The vacuum piston and cover should NEVER be lubricated as it will interfere with normal vacuum piston function. If the piston hangs up, air speed over the jet will be reduced and fuel will not be drawn into the venturi. For good measure, check the float level. If it is set too low, the carb may be running out of fuel under heavy load and going up a hill.
--- 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