Topic: #1 cool until high revs?

[billingstitan]

So, solved the sputtering issue at high revs by replacing points - now I'm running into an issue with the #1 cylinder  not seeming to fire very well at low idle/rpms.

This is a 77 CB550 with PD46A carbs - 98 main jets, 42 idle jets, needles set in the center notch.

I initially thought I'd found the problem as the float was a little off - but rectified that problem, but still doesn't fire right until I start putting the revs on - usually above 5,000 or so it catches and then the pipe heats up fine.

The pilot jet is clean - double-, triple, quadriple checked - can see light through it - used a thin needle to poke through - and blasted it with carb cleaner and compressed air.

The float seems fine - measure the correct height - the bowls now fill the same as the others, which are firing fine.

Getting spark just fine - and timing and carb synch are spot on.

The bike screams at the top end of the rev range - but the pipe runs cooler than the others at idle, low rev - it gets warm, but not as hot as the other three. Double checked points, etc. Not sure what else to look for ... and yes, the idle jet is definitely clean and not clogged.

Any thoughts/advice are appreciated!!

[ekpent]

You have tried a new spark plug I assume. A plug can look OK and still spark but not work correctly under a load.

[strynboen]

inline gas filters can make strange things...to this k3 550...mine ran first real good when i klean the tank 100% and not use ekstra filter

[billingstitan]

Thanks, ekpent - yes, I swapped plugs between cylinders and also bought new ones. No change.

No inline fuel filter on the bike - tank was thoroughly cleaned when I repainted it last summer, and is always kept full with non-ethanol fuel (lucky to live in Montana where it's avail).

Checked the resistance on the plug caps - spot on at 10k - trimmed the plug wire and checked the cylinder compression - matches the others.

Perplexed at this point, don't really know what else to try. I swear this bike is my problem child. Get one thing fixed and something else pops up 

[Duanob]

Sounds like the pilot system in the #1 carb. I am not familiar with the PD carbs but on the older style that's exactly what I would expect. Crud and grit can easily plug the tiny pilot passages. Also ethanol fuel leaves a dry white powedery substance when sitting too long and the liquid fuel evaporates. I've found that in my carb bowls a few times. It could easily plug a pliot jet. Just a thought.

Pull the bowl and pilot and spray some canned air up in the carb body and wire clean the jet and see if that helps. You should be able to do this without removing the carbs?