Idiles, weird throttle response

[atomic22]

Hello

So I've got a problem I searched for and couldn't find an answer to on the boards. Right now my bike is idling, when I give it gas, and it goes past 3,000 RPM it won't come back down.
Happens while I'm riding as well.

Any suggestions?

Thanks
A22

 

[Inked Monkey]

Sounds like an air leak

 

[TeeCat]

Either that, or your ATU weights are hanging advanced. Pull the right cam cover and make sure that the weights snap back to rest. If not, you may have to service the rod that runs through the camshaft and/or replace the springs. There is a thread on 650.com archives about it... I had that issue.

Keep us posted.

TC

 

[atomic22]

Well the ATU weights are snapping back (they are brand new), but I found something interesting when I pulled the cover and I'm hoping it's not too serious .

There was a small amount of oil under the cover and was smoking off. Not enough to notice when the cover was on, but a slight trickle. The engine was hot, and I had gloves on that had some old oil residue on them, but I don't think enough for what I was seeing.

Any ideas, the engine is still staying revved above 3,000RPM. It's like it's the throttle is stuck, even though it's not.

I looked for air leaks, and could not find anything. Also, it only seems to happen when the bike has been running for a while (i.e. over 15 minutes or so).

I'm so sick of fixing this bike right now.

 

[retiredgentleman]

As already mentioned, its likely air leakage around the intake manifold area. Check the lines going from intake barbs to the vacuum petcocks if you have that set-up. If you have any "chirping" that means air leakage for sure.

If the carb sync is not correct, then one side will tend to keep the idle high.

Its also important to do a correct "dead cylinder" adjustment of the pilot screws.

 

[Crab_Cake]

Your carb diaphragms might have a leak in them as well. Take the carbs off and check. When you put them back on make some new gaskets out of gasket paper. Thats what I did and it works like a charm.

 

[Socopunk]

Had the same problem. The answer for me was a number of things. Definetely had an air leak. Spray carb cleaner on either side of the carb, where it boots to the engine and the airfilter, while the bike is idling. If the idle goes up you have an air leak. Like crab cake said, open top of carb and check that diaphragm is not ripped and is seated properly. Also check for a simple malfunction in your throttle cable. I had all three.

 

[atomic22]

Thanks guys!
I'll check all these things and report back.

 

[Sundie]

Air leak in the diaphragm won't cause it to rev high, it will cause it to starve for fuel when it revs, because the slide won't rise.

Have you balanced your carbs yet? Since we're talking ATU's, i'm assuming 38's.

 

[inxs]

Have you balanced your carbs yet? Since we're talking ATU's, i'm assuming 38's.

- not always...one of mine is points, atu and BS34 - original

 

[lateral4]

Mine is having the same issues, it also won't produce much power under 3,000 rpms. If I'm at a standstill and I roll on the throttle to take off it will bog down and sputter, but as soon as it hits 3,000 rpms it takes off. Are you having this issue too? I can't figure out what's going on with it.

 

[weekendrider]

lateral4, try cleaning the pilot circuit. Then check the level in the float bowls.