Chaising the infamous hanging idle - Carb tops possibly?

[robinc]

Grasping at a straw here along the lines of what Peanut was saying. Maybe you have overtightened the carb mount screws.

I have a set of 74/75 BS38'S that if I overtightened the carb mount clamps screws, the butterflies would bind and not fully return. Had to play around with them to get them just right.

Worth a try to back them off a bit before you throw in the towel.

 

[Bob Kelly III]

Well SCi..... when You do everything 3 or 4 times and it always turns out the same you simply ain't found it yet !
the problem is in there somewhere.... where is anyone's guess at this point.... i'm sorry to say.... perhaps a new set of carbs is the way to go for you !..... don't expect to just drop them in and be done with it though You'll need to set the floats and check the jet sizes
and the operation of everything before you put them on the machine !
....Good luck, I wish I could help but I don't have any idea at this point !
Bob.......

 

[Sci85]

I know guys. I'm no expert but I've rebuilt and jetted countless carbs. Raced motocross for years. I am just as baffled as you. For whatever reason, these carbs just want to fight me. I dunno, maybe I damaged them somehow over the years building this bike. Right now, it appears the throttle shaft is messed up someway. The outer seals are new OEM but still seem to be leaking. Or, possibly, there's some other issue that's not carb related. I hate to spend the money but I'm gonna pull my hair out if I don't try a different route.

I appreciate everyone's input and assistance and I'll keep ya posted as I make progress. I gotta turn my attention to brakes and clutch issues for a bit...

 

[Sci85]

Well, I bought another set of carbs from a supposedly running bike. Cleaned them all up, put them on the bike and....f%$k. Still idling high! Spraying indicates shaft seals like my original set. How can anyone have this kind of luck!?

Any recommendation on shaft seals? I used OEM yamaha seals on the other set of carbs and that didn't solve the problem on that set. I guess I can try again on these carbs but only if they are going to work. Man this thing is killing me. Never had such problems with any other bike...

 

[Sci85]

Well after 3 trys I've finally gotten her to a ridable point. I ended up replacing one of the slide diaphragms and went to a larger pilot (47.5's) and that seemed to help a lot. I might swap both diaphragms for brand new ones. She still has a very slight tendency to idle hang just a bit but not enough to be an issue. I'm gonna just ride her for awhile and enjoy it. This winter I think I'll switch over to the newer Cvk's. Thanks again for all the help guys. Much appreciated!