Is my bike posessed?!?!

[BoulderBiker]

So my bike started doing this very strange thing the other day. I was idling it happily whilst donning my helmet to ride to work and all of the sudden the engine just roars up like its got full throttle. I promptly hit the kill switch and then start it back up after checking choke and throttle. starts back up to a normal idle.

In the days since its done that a few times and almost always shortly after starting the bike, each time roaring up like its got full throttle.

I took the carbs apart yesterday to make a few adjustments to the jetting since the bike has been running rich since I first put the jet kit in awhile ago. I checked the everything out while I had it apart and it didn't feel like anything was really sticking, but who knows.

Anyone ever heard of this? This happened once when the choke wasn't even on and the throttle seems to have a nice smooth return.

Thanks!

Anthony

[max]

yes. it is possessed

Mine used to do that when i first got it about a year ago. After about 30 seconds of idling in the morning it would sometimes jump to 6 or 7k rpms. After restart, everything was cool. Usually happened about once a month or so. We could never figure it out, but after all the carb, electrical and exhaust work I did since then it hasn't happened in the past 4 months or so.

Damn gremlins, man

[snowbeard]

hmmm. mine does a sort of that, but I usually have the throttle cable tightened. I start it, it chuggs along, I tighten the throttle cable at the handlebar, start to put on helmet, jacket, and it races up to 4K. I'll back it off and it idles ok.

but it's a bear to start in the cold anyways, and I can't argue the carbs need a good cleaning

[chef1366]

Diaphragm issue?

[putzkrieg]

It could be a problem with the choke, mine was doing that for a while until I adjusted the choke to close completely. If it's open at all sometimes it just increased the revs exponentially until I had to hit the kill switch. Just a suggestion.

[Nessism]

As the others have mentioned it's most likely the choke - which isn't a choke at all on these GS mikuni carbs. It's fairly common for the engine speed to race once it reaches a certain point in the warm up cycle. Another common cause of high/irratic idle is vacuume leaks - most commonly from the carb boot O-rings.

[tconroy]

As the others have mentioned it's most likely the choke - which isn't a choke at all on these GS mikuni carbs. It's fairly common for the engine speed to race once it reaches a certain point in the warm up cycle. Another common cause of high/irratic idle is vacuume leaks - most commonly from the carb boot O-rings.

Im with nessism on this one,I would check for leaks on the carb to engine side.Look for cracks or seperation in your intake boots if they are old.This problem wont show up untill its warmed up.If you have'nt change your o-rings I would do that,but firts test the boots with wd-40 or a water mist bottle to see whats up.

[Dunkin]

Sounds like your choke plunger could be sticking and as your engine warms up and you back off the choke at the handlebar the plunger just is not moving back. Might be the cable or plunger.