High RPMS

[jimb]

I have a `80 xs1100 midnight special. It idles "resonably" well when started but revs high then stays there when taken for a ride. Pretty hard to shift at 3500 or 4000 rpm. Must hold brake pedal down with clutch half way engaged while stopped at a light. Any suggestions??

Thanks,

Jim

[motoman]

Originally Posted by jimb

I have a `80 xs1100 midnight special. It idles "resonably" well when started but revs high then stays there when taken for a ride. Pretty hard to shift at 3500 or 4000 rpm. Must hold brake pedal down with clutch half way engaged while stopped at a light. Any suggestions??

Thanks,

Jim

......uhhh......turn down idle screw and not hold brake with clutch partly engaged while in gear.

[MarkD]

Jimb-- did you clean and rejet the carbies using genuine Mikuni jets?

[Radioguylogs]

Rising RPM when hot is consistent with an air leak in the carb boots or butterfly shaft seals....

Can sniff with lighter fluid, starter fluid, or unlit propane. If the RPM changes when you wet one of these areas, then you found your problem.

[jimb]

The carbs were cleaned and reset by a local Yamaha dealer. Don`t know what jets, if any, they used. New carb boots were installed as well as one new valve guide. Had someone else look at the problem who thinks maybe the carbs themselves are bad? Can`t keep spending money on a fix. Retired!!!!!

[Bonz]

Does it idle around 1100-1200 (or at some speed lower than 3500-4000) when just starting out but warm enough to not need choke?

Like was said, idle speed screw may be your issue? Look forward to an update.

[jimb]

That`s exactly how it works. It`ll idle around 1200 then all you have to do is ride around the block and the idle is up around 3000 or4000 or what ever you "rode it" up to. Really frustrating!

[Bonz]

Double check there isn't something hanging up mechanically with respect to the carbs closing. Even if the throttle snaps back, check the butterflies are closing all the way. JAT.

I am leaning more toward adjusting the idle speed down after it is warmed up but before going for a ride.

Does the idle creep up if you let it warm up for an extended period of time, or stay low until you ride?

Did the mechanic write down what settings (how many turns out from lightly seated) he used on the pilot screws (fuel screws)?

[Rasputin]

Check the plug color after you ride it a few miles and the idle will not come down. My bet is that they will be chalky white. Sounds to me like they set the low end mixtures/jets to lean. If they used one of those sniffer type machines to set up the carbs, I will damn near guarantee it is set too lean. That is not good as you will burn a piston and retirement income will suffer badly, if you even want to try to fix it after that.

[Bonz]

Here's the 4-day bump...

[AggiesaurusRex]

I'm having this exact problem. It idled fine until warm ( basically as soon as you take off) then the idle shoots way up and stays there. There is no obstruction or tightness on the cable. The main idle speed screw is backed all the way off so its not touching anything, so it can go no lower. Yet the idle is super high. Its too fast too really shift. If I start in second its like I have cruise control, I can let go of the throttle and I maintain my speed going down the back road. when I pull my clutch in, it takes off and I just shut the bike off.
It sounds like this is a lean setting symptom? (Also, I heard popping in the beginning) Am I just richening the idle screws on each carb? Replacing the pilot jet with a larger size? Banging twice, bounce on the seat, and kick the tire 3 times before starting?

[natemoen]

Creeping idle/hanging idle is also a sign of a lean fuEl mix.

I too though would start with just turning the idle adjuster down after it has jumped up.