Idles super high when choke off.

I have a 77 650C, I rebuilts the carbs and jetted them bigger with the Z1 kit they sell for the bike. It has 4-1 exhaust, and pod filters. When I rebuilt the carbs last year and got the bike running, exhaust with no baffle, bike ran fine choke on, let it warm up, choke off, took it for a quick spin, idle was perfect. Took carbs off and started my bike project. Last week when I put the cabrs back on I noticed they got stuck, lubed them and set them free. Slapped them back on the bike, this time exhaust has a silencer(I have to cut silencer shorter since now its like a straight pipe). Friend came over gave me some gas got the bike started first kick, choke on/cold start. Idle was at about 2-2500, we let her warm up and then choked it off and the bike started to idle super high past 3k, so I set the idle screw so that it would idle at 900-1000. Everything seemed ok then boom it started to spike up again. So with choke on the bike sounds fine. Also he noticed that when I pressed the front brake and light would turn on, that bike sounded like it wanted to die and at one point I saw idle got to 500.
So does anyone knwo whats up? I didnt mess with anything as far as engine and carbs since the bike was running last year, other then carbs being stuck and me freeing them. I did have a small exhaust leak from header, I think I need to check the nuts make sure they on tight.



At one point we thought maybe throttle cables were too tight and when we moved bars it reved the bike, but that wasnt the case.

You could have a vacuum leak, if the bike is running rich and has a slight vacuum leak it would idle high...my friends buell did that till the vacuum leak got worse then the pipes got red hot and ended up seizing.

I know my carb boots have some cracks in them but they didnt seem to be holes. if they are cracked bad could that be it?

JonnyC wrote:

I know my carb boots have some cracks in them but they didnt seem to be holes. if they are cracked bad could that be it?

Yes, that could do it. One way to check for leaks is to spray some WD40 around the boots while the engine is running. If the RPMs drop and/or you get white smoke from the exhaust, then you have a leak.

Some people use starter fluid, but it's a bit more dangerous to be spraying it around a hot engine. With starter fluid, a leak would cause the RPMs to shoot UP.

Ok I will try that now, I ordered new ones anyway from Z1.