Increasingly high idle from cold start...

[BA80]

Gas fouls them, turns 'em freakin' black.

Ha ha ha.......that in no way was a racist statement. (disclaimer for the PC crowd)

[JackPanzer]

Well I've synced them everyday this week and it starts cold just fine and idle dandy until I get her moving. Take her down the block about 1000 feet and pull the clutch in and back to high revs. Gonna take carbs back off and make the needle jets a bit more rich. Any other advice? Wanna get the idling lean issue fixed before I fully sync the carbs. And this is with no choke and idle screws at 1 1/2 turns out.

[JackPanzer]

Well I've synced them everyday this week and it starts cold just fine and idle dandy until I get her moving. Take her down the block about 1000 feet and pull the clutch in and back to high revs. Gonna take carbs back off and make the needle jets a bit more rich. Any other advice? Wanna get the idling lean issue fixed before I fully sync the carbs.

On a side note: when I first got the bike she ran way rich. Carbon deposits and black smoke everywhere. Is it really that big a jump in jet size to get her running right?

[BA80]

The jets won't make a BIT of difference in idle speed. You have another issue.

Don't change any internal components until you figure out what that issue is. Listen or not. Just saying

[JackPanzer]

The jets won't make a BIT of difference in idle speed. You have another issue.

Don't change any internal components until you figure out what that issue is. Listen or not. Just saying

I'm listening...just trying options. Haven't bought or changed anything but syncing the carbs. Haven't found any air leaks from spraying wd40 when it is idling quietly. Sorry, just need to be patient.

[CaptonZap]

Next time you have the carbs off, make sure that the bolts holding the rubber carb boots are all tight, and if you want to be sure, take them off, clean the flange faces, put some Hi-Tack, Yamabond, etc, on both faces, and re-install the boots.
It sounds like an intake leak, which gets worse when the head heats up.
My 80G did the same thing, and on inspection, the inner bolt on the #3 boot was missing.

CZ

[BA80]

Been there CZ. The damn leaky paper gaskets need to go and just some 3bond in there.

This REALLY sounds like a sync problem to me. Even leaky intake gaskets wouldn't be that bad and binding linkage would be there all the time.

[rdmcguy]

Just a thought

Have you done any kind of a plug reading?
Do you know if it is more than one cylinder?
Kind of a primitive idea here but...
pull a plug cap or two to see if you can isolate which cyl.If you can determine if it is only one or two cylinders(carbs)you can compare to the adjacent ones to determine what may be different between them
Don't forget to put a spare plug on the disconnected ones and wedge or secure them to metal(head) no point in frying a tci.
Joe

[JackPanzer]

I'll get a plug reading next weekend I don't work. All four cylinders are firing and all boots are airtight I believe. Will check again tomorrow after work.

[JackPanzer]

I've been reading about the idle mixture screws having o-rings on them. My bike hasn't had them since I got it. Just wondering if it may be adding to my problem?

[motoman]

I've been reading about the idle mixture screws having o-rings on them. My bike hasn't had them since I got it. Just wondering if it may be adding to my problem?

Not unless the later carbs got swapped in it, which have the recessed mixture screws. 78-79 carbs had exposed mixture screws and no washer/O-ring.

[mack]

Sf

I got lost reading this thread. If I understand correctly, initially when you fired up the bike it would rev up immediately and you'd have to shut it off.
But now it will idle fine, but when you try to ride it, the reve's have creeped up? To what rpm?

[JackPanzer]

I got lost reading this thread. If I understand correctly, initially when you fired up the bike it would rev up immediately and you'd have to shut it off.
But now it will idle fine, but when you try to ride it, the reve's have creeped up? To what rpm?

Right.

I don't know about the rpms, no tach.

[mack]

Linkages

I've run into this once. And what caused it in my case was the butterfly in the #3 carb was not properly centered in the throttle shaft. Once the butterfly was opened to a certain gap it would bind on the wall of the throat. Had to drill the screws out and slide the shaft over a bit and replace the screws. Didn't take long to perform but finding the cause was a lot of fun. I'd have a close look at the linkages as well. Something is hanging up my friend.
Same thing was going on with Dwaynes bike at the north rally a couple years ago but it turned out to be dirty linkage on the rack. I know yours are spotless by now so we can rule that out in this case.