CB500 Four 1976- some issues!

[exelbyt]

PROGRESS REPORT;
I have now sorted all the issues by replacing the sprocket to one closer to stock (35t) and rebuilt the carbs.

The latest issue is to do with tuning the carbs.  I have scoured all the threads on sohc and found a wealth of information about carbs etc.

I am currently running
100 main, 40 idle jets
1 and half air screw
Clip position 4/5
With the same exhaust and air filter from the picture about.

It still isnt running right.  There is a flat spot which occurs at 1/2 throttle and since i change to 100 main jet (from 130) it has been stalling intermittently at idle after a short run. Up until 1/2 throttle it seems to purr fine, but after 1/2 and about 5000revs it doesnt seem to be firing on all cylinders.

Any thoughts? Or any good ideas on where to look for advice?

Thanks!



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[JamesH]

Are you running the stock factory Airbox and intake stubs?

[exelbyt]

No using pods, i have checked the plugs and they all seem to be healthy and clean!


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[exelbyt]

So - i have changed the clip position back to the middle (3) position and run the bike (air screw out 1 turn). It was still running a bit rough around 1/2 throttle and 5000rpm. I then tried it with the choke open 1/4 and that made a big difference, it was running much better.  I also tried it with the choke open 1/2 and then with the air filters off, but this was less successful. 

Hopefully this is adding to the picture of the biked issues, maybe someone has an idea how to sort it out?


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[Spitfire]

Here's a chart showing the relationship between throttle opening and jets, may be of some use.


Cheers

Dennis

[Tomb]

i have checked the plugs and they all seem to be healthy and clean![img width=1000 height=750]

But at what throttle opening? Spitfire's chart is a good example of why we need to do plug chops at all throttle openings. So many times I've heard lads saying "I took it out for a run, got back and whipped out the plugs, they look ok/rich/lean"  ....So what you have done is check them at tickover, coz that's the last thing the engine did, the last throttle position before you shut it off.

And if you DID do proper plug chops I'll get me coat