need help!!! high and low idle

I'm looking to buy a 2000 650R and it seems to run fine but idles high and then idles low and then you give it gas and the idle goes back up then eventualy back down, and any others thing I should look for on this model, can use any tips.

Hey Joe, are you sure you want to buy one of those BRP's. It's not a little sissy bike like that CRF450. I'd hate to see you get hurt. :D:):D

Could be anything:

1. bike running lean

2. dirty carb

3. cables binding

4. etc...

Any mods been done to the bike?

That year bike has a few easy fix problems, starting with the counter-shaft seal.


Carb may need cleaning, Throttle cables worn or need lubed, Throttle tube draging, Is it uncorked, Air filter clean....... :)

Mine did that when it was brand new. I adjusted the idle down to correct speed using an inductive pickup around the plug wire to set rpm correctly. My theory on why this happens is that the cdi box has an ignition advance curve mapped into it. If the idle is high enough to make the ignition timing advance, then the rpm goes up as a result. rpm goes up and ignition advances some more. When you wack the throttle and it slams shut, the rpm gets low enough to get out of the ignition advance curve and will sometimes idle there. Hey, it's just a theory but I have seen the same thing on race cars were it seems half the "carb" problems I find are related to the ignition timing. So much so that I have a habbit of running locked ignition timing on most (OK, all) race engines I tune. At any rate, I wouldn't let it scare me away from a bike.

I guess I should have clarified by race engines I mean Chevy V8's and the like in drag cars and a couple dirt burners, not bikes. Sorry if that was confusing.

Hey Topolino, I want some of what you've been smoking! :D:):)

I bet you do

Haha! Seriously though, the reason big thumpers die when you open it all the way at low RPM's is because there isn't enough vaccum created to pull in adequate fuel. If you have a pumper carb, you can solve this problem 100%.

I found that the bike has cable routing issues ,left turn engine revs up ,right turn decomp cable is pulled engine shuts off, no big deal , filter is clean and oil looks good, but, the problem is with the bars straight and no binding the idles is up and down and as long as I don't hear problems with the idle due to valves or something major I will get it ,crf 450 the same symtoms = intake valve problems , so any more input to known problems will help, thanks again and btw jack it's time for me to step up to the big bore, we are racing the baja 500 & 1000 and nothing less than a 650 will make it

Typically if you're just riding along and cut the throttle and she idles high and doesn't come down quickly this is referred to as "run on". It is caused by a lean pilot. However, if your's is a routing issue than I guess you're all set.

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