Topic: CB550F - Tuning questions

[The Sovereign Man]

I’ve just rebuilt my carbs and the bike is running like a clock .... mostly. There’s just a couple of little niggles I’m hoping to resolve.

• Hard to start when cold (bike was difficult to start previously)

• Revs hang about 500rpm above idle before settling when pulling up to a stop. Not evident when blipping the throttle

• Burbling (only momentarily) just off idle when leaving from a stop. Not evident when more throttle used

Aside from this, the throttle is smooth as butter and the idle sits beautifully. Bike pulls hard all the way to redline, and I saw 110 on the speedo for the first time ever.

I’ve only bench synced the carbs at this stage but wanted to get some opinions before vacuum synching.

All advice appreciated.

[kerryb]

What airbox/ filter are you running?   I went through similar issues with my '77  550F when I was trying to get it to run well with cheap pods on it ( only got close!)  It was hard starting and burbled/ hesitated at small throttle increases.
But...it would pull hard all the way to redline.
Hanging idle was improved with vacuum synch of carbs, but not cured until I Tightened up the springs on the advancer
The real fix was putting a stock airbox on, now it does everything just right!
Note:  before you spend a lot of time on the carb tuning, get the timing just right and check your advance with a timing light.

[The Sovereign Man]

What airbox/ filter are you running?

Factory airbox.

[kerryb]

Good, that will make things easier.  Check your ignition stuff, maybe tighten up the advancer springs, and do a vaccuum synch.  I haven't read your posts in a while, but I assume  you have ruled out vaccuum leaks in the intake system.

[The Sovereign Man]

Good, that will make things easier.  Check your ignition stuff, maybe tighten up the advancer springs, and do a vaccuum synch.  I haven't read your posts in a while, but I assume  you have ruled out vaccuum leaks in the intake system.

Fairly positive there's no leaks. Will take a look at ignition timing today, if I get a chance.

[The Sovereign Man]

Now number two carb is pissing fuel out the overflow. Chasing my #$%*ing tail with this bike.

[RAFster122s]

Are you certain the jets are clean? They need to be spotless. Deposits can build up just beyond the jets, this the need to pull the jets and run them through a good ultrasonic cleaner with a good cleaning solution.

 Sounds like your rubber intake to carb boots might not fit correctly allowing air leaks.
Did you change the O-rings in the intake runners to head?

Carb cleaner sprayed at the boots and head to intake runner seam can tell you if you have an air leak if the engine running changes when you are spraying the cleaner.

[The Sovereign Man]

Are you certain the jets are clean? They need to be spotless. Deposits can build up just beyond the jets, this the need to pull the jets and run them through a good ultrasonic cleaner with a good cleaning solution.

 Sounds like your rubber intake to carb boots might not fit correctly allowing air leaks.
Did you change the O-rings in the intake runners to head?

Carb cleaner sprayed at the boots and head to intake runner seam can tell you if you have an air leak if the engine running changes when you are spraying the cleaner.

I’m 100% positive the jets are clean.

I did not change the O-rings in the intake runners to head because I never took them off.

I’ll try the carb cleaner spray trick and see what happens.

[The Sovereign Man]

This bike is such a #$%* to work on. I’m beginning to dislike it.

[Deltarider]

Now number two carb is pissing fuel out the overflow. Chasing my #$%*ing tail with this bike.

In most cases it is easy to fix.
1) Tap #2 float chamber with stub end of a screwdriver and hope this will free dirt particle from between the valve and the float needle's tip.
2) Drain #2 float chamber and leave the drain screw open. Now open and close the petcock a few times and hope dirt particle from between the valve and the float needle's tip will be flushed. Collect fuel.
3) combine 1) and 2).

[RAFster122s]

Well, those O-rings are likely to be hard and flat and leaking. Plull your carbs again and change out those O-rings. I bet they will break out like pieces of plastic when you go to replace them.

[Deltarider]

Well, those O-rings are likely to be hard and flat and leaking. Plull your carbs again and change out those O-rings. I bet they will break out like pieces of plastic when you go to replace them.

I'd leave them alone until you have indication one leaks.

[seanbarney41]

This bike is such a #$%* to work on. I’m beginning to dislike it.

yeah? cry us a river lol  I will trade ya for a vf500f, than you got something to cry about!

No, seriously.  That small sohc4 airbox can be a real pain in the ass.  But with some practice, it is not the worst.

[The Sovereign Man]

I believe I may have found the issue (or one of) ...



The split/s go all the way through to the inside.

Would this be enough damage to the boot to cause me some tuning headaches?

I suspect this happened whilst I was bashing my knuckles and swearing a little under my breath, AKA wrestling the carbs back on.

These were perfect when I took them off.

P.s. I can also lift heavy stuff and swing hammers.

[RAFster122s]

That's probably not your issue as it is the boot between the carb and the airbox. Lean run ng condition is caused by leaks between carbs and head. Likely either your intake manifold O-rings or carb boots. Old boots that are hard can sometimes leak air  even when the clamps are tight because the boot is not compressing  around the carb or the intake manifold. If your manifold boots are old buy a new set from South Sound Honda of Olympia Washington, lower prices and economical shipping charges. Bike is from 70s and you don't know if they are original unless you changed them already. Aftermarket boots are junk in no time...so don't waste your money buying twice.