Honda Z600 Experiments

[Oleotwo]

Hi all.
It has taken a while, but I have discovered some things by trying to get my little Coupe started and running properly:
I. ENGINE (with 84,000 miles) WON'T Start
The cam had jumped to the point that the crankshaft was over 90 degrees retarded (same as camshaft advanced?). My previous vain attempts to reach the redline, both while driving and while in neutral had apparently not been a good idea. Given the erratic and bucking way the engine ran, I see no certain way to tell which direction the chain actually jumped. That is, the crank could have retarded by 90 degrees or advanced by 270 degrees (!) and wound up in the same place. I am assuming the latter would be unlikely--if only as a way to preserve my sanity.
I was able to re-time the cam by "slipping" the chain one link at a time from the rear while pulling up all the slack off the tensioner. Unfortunately, I did not count the links, but it took at least seven links to align the marks.
The engine then started right up and ran fine. On the road, it made the red line for the first time.
Because of the possibility that the factory marks might be wrong, I then played with 5 settings: one by the mark and two on each side. The results were amazingly small. It is quite conceivable that there are cars out there with mildly distorted cam timing that the owners have not much noticed.
The cam notch is fully visible in the "window" in three different settings. I found that the engine runs best with the notch fully visible, but one link towards the rear of the engine rather than in the center.
Other settings resulted in hotter running, occasional pops out of the exhaust, or generally poorer running.
The "bucking" or engine speed variation never recurred.
Through all of these tests, I never played with the ignition timing.
Conclusion: I have an old, stretched timing chain. IF ANYONE HAS A CHAIN WITH A MASTER LINK AVAILABLE, PLEASE LET ME KNOW.
II. CARBURETOR SPIT BACK
Through all of my earlier efforts, gas spit out the carb intake more and more. Re-timing the cam quite simply put a stop to this problem. I figure that if an intake valve opens and closes late, then some compression will be pushed out the carb. And if the intake valve opens and closes early, then some exhaust will be pushed out the carb intake. Either way, you get gas spitting out.
As a side note, once I tried an S.U. carb on the Honda, while it solved none of my problems, I did get the impression that it would be a worthwhile conversion if I could get the hood closed.
III. COMPRESSION
My compression was 160/165 and ran poorly.
Then compression went to 120/120+ and did not run.
Now it is 150/153 and now runs well.
Whether the cam is advanced or retarded, it does bad things to the compression stroke. From these readings, I cannot tell if my valves bent or not. And, what caused the initial readings to be above specs???
Overall, it has been much more fun working and seeing positive results than it was working and seeing thing go straight down hill.
Fred Zampa
Macon, Georgia
Phone XXX-XXX-XXXX
fzampa@...

[lyletrudell]

Fred, good news for you and good info.
Sounds like your car will be fine once you get a new chain and re-check the cam timing.
Wow, that's too funny, the Honda engine will still run with the chain off one tooth. The worn/stretched chain is retarding the timing, so advancing the timing one tooth might compensate, not a good way to do it.
Fred your probably right other Honda owners could have their cam timing off.
So the cam has 34 teeth, the crank must has 17, the cam turns 1/2 the RPM of the crank.
360 divided by 34 = 10.6 degrees per tooth.
So it's off 10.6 cam rotation, 21.2 crank rotation.
If I figured right how can it run that far off, not good for sure!
That's why people degree the cam and use adjustable cam gears.
We only have 36 HP with everything set perfect, how much when it's off! I have only test driven my Honda 600 in a very small parking lot.
It was really slow, but it was running really bad......
I hope!
Lyle

--- In
2cylinderhondas@yahoogroups.com
, fred zampa wrote:
> Hi all.
> It has taken a while, but I have discovered some things by trying to get my little Coupe started and running properly:
> I. ENGINE (with 84,000 miles) WON'T Start
> The cam had jumped to the point that the crankshaft was over 90 degrees retarded (same as camshaft advanced?). My previous vain attempts to reach the redline, both while driving and while in neutral had apparently not been a good idea. Given the erratic and bucking way the engine ran, I see no certain way to tell which direction the chain actually jumped. That is, the crank could have retarded by 90 degrees or advanced by 270 degrees (!) and wound up in the same place. I am assuming the latter would be unlikely--if only as a way to preserve my sanity.
> I was able to re-time the cam by "slipping" the chain one link at a time from the rear while pulling up all the slack off the tensioner. Unfortunately, I did not count the links, but it took at least seven links to align the marks.
> The engine then started right up and ran fine. On the road, it made the red line for the first time.
> Because of the possibility that the factory marks might be wrong, I then played with 5 settings: one by the mark and two on each side. The results were amazingly small. It is quite conceivable that there are cars out there with mildly distorted cam timing that the owners have not much noticed.
> The cam notch is fully visible in the "window" in three different settings. I found that the engine runs best with the notch fully visible, but one link towards the rear of the engine rather than in the center.
> Other settings resulted in hotter running, occasional pops out of the exhaust, or generally poorer running.
> The "bucking" or engine speed variation never recurred.
> Through all of these tests, I never played with the ignition timing.
> Conclusion: I have an old, stretched timing chain. IF ANYONE HAS A CHAIN WITH A MASTER LINK AVAILABLE, PLEASE LET ME KNOW.
> II. CARBURETOR SPIT BACK
> Through all of my earlier efforts, gas spit out the carb intake more and more. Re-timing the cam quite simply put a stop to this problem. I figure that if an intake valve opens and closes late, then some compression will be pushed out the carb. And if the intake valve opens and closes early, then some exhaust will be pushed out the carb intake. Either way, you get gas spitting out.
> As a side note, once I tried an S.U. carb on the Honda, while it solved none of my problems, I did get the impression that it would be a worthwhile conversion if I could get the hood closed.
> III. COMPRESSION
> My compression was 160/165 and ran poorly.
> Then compression went to 120/120+ and did not run.
> Now it is 150/153 and now runs well.
> Whether the cam is advanced or retarded, it does bad things to the compression stroke. From these readings, I cannot tell if my valves bent or not. And, what caused the initial readings to be above specs???
> Overall, it has been much more fun working and seeing positive results than it was working and seeing thing go straight down hill.
> Fred Zampa
> Macon, Georgia
> Phone XXX-XXX-XXXX
> fzampa@...