Topic: '75 CB550 Idle Issues

[sniper1]

Did you check the dials with a common vacuum source to make sure they read the same with equal vacuum?
 I didn't, do you have any recommendations for a source. The guages are relatively new, only used them on my '77 550 once.

The slide linkage components are not completely rigid. Pushing on these bits will make the engine run oddly. 
Any reason why pushing on #3 & 4 would cause it to die, and pushing on # 1 & 2 it still runs decent?

Did you eliminate carb coupler leaks?
I did.

Were the dial readings different before adjustment? Yes, mostly the #4 carb. Any reason why increasing or decreasing the screw on the #4 would make the bike rev really high? Could there be a vaccum leak somewhere else that I'm missing?

[TwoTired]

Did you check the dials with a common vacuum source to make sure they read the same with equal vacuum?
 I didn't, do you have any recommendations for a source. The guages are relatively new, only used them on my '77 550 once.

You just need a 5 port manifold.  Connect all the gauges to the manifold and then connect the manifold to on single port.  All the gauges should read exactly the same.  And aquarium supply should have  a serviceable manifold.

The slide linkage components are not completely rigid. Pushing on these bits will make the engine run oddly. 
Any reason why pushing on #3 & 4 would cause it to die, and pushing on # 1 & 2 it still runs decent?

Probably, but, I don't see why it would be important.

Were the dial readings different before adjustment? Yes, mostly the #4 carb. Any reason why increasing or decreasing the screw on the #4 would make the bike rev really high?

Sure, you could be transitioning between all cylinders firing evenly from only running on three.  Or making one cylinder contribute way more than the rest.  Getting all four to cooperate with the same strength is what vacuum balance is all about.

Could there be a vaccum leak somewhere else that I'm missing?

I can't tell from here.

If the carb couplers aren't leaking as you reported, maybe the o rings between head and intake manifold are.  Just a guess.

Cheers,

[XLerate]

As mentioned in the carb cleaning instructions, being careful of no sparks or flame present in immediate area of highly flammable fuel, playing the UNLIT gas jet from a propane torch all around intakes and cylinder head will cause rpm change wherever there's a leak. Blowing it into carbs, air filter or filter box etc, will also increase rpms because of propane fuel.

If no torch is handy WD40 will do, but will be a little messier. Either one causes engine to speed up wherever there's a leak.

[sniper1]

I'll give that a try, probably tomorrow. I'll report back then.

Thanks.

[XLerate]

Normally you could also use carb spray cleaner which of course dries with no mess, but seems to me you painted carb bowls or something so it would screw that up. Any of the three are a simple & foolproof test.

[adrian]

Was this resolved? Im having the exact same problems!!! Every single thing is happening on my cb550 1977