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CB 500 Four - engine problems

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davidcumbria:
I wonder if the rattling noise is due to the well documented issue of wear in rocker shaft bores of the valve cover due to rotation  of the shafts. This will produce inconsistent valve clearances and can be seen looking at the end of the rocker shafts. This can easily be checked by removing the small end covers in the first instance. Later bikes had pegged shafts to stop the rotation and I have a spare such cover.

I solved my cool number 1 cylinder by reducing the pilot jet to 35.

 Another possibility for the noise is related to the cam chain tensioner. The blade on mine had eventually broken off and was found in the sump.

K2-K6:
Listening to audio, through headphones, and it sounds like one or more cylinder isn't running at idle, it doesn't start as you open the throttle either.

What this usually causes is to adjust the rpm at idle too high in keeping it running, then if tge cold cylinder starts the rpm simple goes to tge higher position from having all running.

From characteristics shown, there's intermittent running of some cylinder which will need the cause identified to progress.

K2-K6:
Diagnosis, the need to seperate electric from fuel is priority in helping to solve this.

Start from cold, run  20 sec then switch off. Check exhaust for cylinder temperature to find which are cold. Swap a "hot" plug with a cold one, then repeat to see if the problem transfer across between those two.

If it stays in the same place (the fault) then you can swap plug leads over. If fault is on #1 then swap the plug lead over with #4 to, again, see if the fault moves. Same if it's one of the two middle cylinder 2 & 3 that show fault.

If you've two cold and consistent with 1 coil of ignition, e.g. both 1 & 4 then you're ordinarily looking at that whole set of ignition. The points, condenser, leads and coil &  caps for that set.

If absolutely none of this has any effect, then it's likely in the fuel system.

Charliecharlcomb:
I had a misfiring problem that wouldnt go away and after cleaning the carbs and replacing the brass, I realised that the needles need to be changed as well as the replacements are subtly different. I went back to my original brass and needles and after all the cleaning and balancing it runs beautifully again.

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