KLX 650C - high idle, hot and lean

Hey folks, great resource, been browsing a while but this is my first post.

I've got a 95 KLX 650C that was super dependable until about two months ago when it started causing trouble. I'll skip right to what it's doing now:

It's extremely picky about mixture when starting cold and it doesn't start easy but I can get it running before the battery dies if I'm lucky. Once it's going I need to make sure it stays above about 1300rpm or it'll die immediately (a little higher than it used to need). If I rev it to 3 or 4000, it's a little slow coming back down to idle and as it warms up it gets more and more reluctant to come down. Once it's fully warm, it won't come down from 3000 at all unless I shut it off and restart it. Then it'll idle fine at 1300, until I rev it again.

It's on it's third plug since the trouble started. All of them fouled with classic symptoms of lean mixture.

It seemed to me like a sticking slide so I pulled the carb and the thing is pristine. The slide moves like silk, jets look perfect, float looks good, everything looks to me exactly like it's supposed to. Cleaned everything up anyway, replaced the plug and air filter, checked that fuel flows from the tank ok, put it all back together, same issues.

The plugs are fouling pretty fast. For a while I was able to drive it before the issue got really bad but now it's pretty much unridable so it's hard to say how many miles it takes to fowl them but I got maybe 100 miles on the second plug.

I thought I had enough ideas to get to the bottom of this but I've run out and still can't find anything wrong. Any suggestions of what to try next would be greatly appreciated.

Edited by apdg

Two things, possibly valves too tight and possibly the cam chain tensioner is allowing variable valve timing. I had idle and starting issues when I had the cam chain tensioner crap out at 14,000 miles, the SECOND one! We rebuilt the top end for the burnt valves and trashed cam chains (2 in the 650) and I put in a manual tensioner - 30,000 miles and four adjustments ago (3 were due to the new chains seating in. That and my Zephyr were the reasons I got into making manual tensioners for the 650 and other Kawasakis.

Mine would pop and backfire quite loudly out of the muffler. If you have cam drive rattle you need a manual tensioner. Contact me if you need one. Mine is about 1/2 the price of others if they even list the KLX.

One other thing people don't want to believe, but with 12 years experience with it, I recommend a Dial-A-Jet from Thunder Products to take care of lean carburetion. Mine has worked WITHOUT ADJUSTMENT through an opened up air box, installation of the big bore Vulcan piston, and a full reverse cone megaphone exhaust. It also compensated for running from 18 degrees to 95 degrees as well as going from sea level at Daytona Beach to about 5000 feet in West Virginia again with no adjustment. Nice chocolate brown plug every time and good exhaust tip color too. Others on the Yahoo KLX650 group have also had very good results with the Dial-A-Jet. Read up on it and the magazine testing (Dial-A-Jet does no advertising in the bike magazines so there is no BS in the articles). Highly recommended over having to go through the headache of jetting. I have 45,000 miles using the DAJ. I will be putting one in my SR500 street tracker when completed.


I was wondering if you got to the bottom of this problem, as mine has started doing exactly the same! It doesn't sound like the cam chain is rattling, but i am interested in buying a manual tensioner anyway if anyone knows where I can get one either in the UK, or shipped out here at a reasonable cost? My KLX is unridable in it's current state so am using the Ninja instead, but would like to get this sorted.

Many Thanks,


Somehow I missed the notice when KLX678 posted his reply so I just now saw that suggestion. It's not something I had considered before but at low RPM (when I can get it) I am hearing rattling so I'll try that next.

Unfortunately, no, I still haven't gotten to the bottom of the problem yet. On the advice of a friend, I did a couple more carb cleaning tricks and put a bit of two stroke oil on the slide to see if that had an effect before it got blown off (it didn't really). I checked that the engine wasn't sucking in extra air through the boot on the engine side of the carb and rechecked the jets. All that still looks ok.

I'm far from an expert but can a loose timing chain cause the idle to get stuck high like that? I can see the plug fouling and the difficult starting but the idle I can't quite picture. Right now it really only backfires when it's failing to start. Once it's running it sounds perfectly smooth and even. In any case, there are enough symptoms that I'll be doing the manual tensioner conversion this weekend. Thanks for that suggestion! I like to make stuff so I'm going to try the modification of the automatic tensioner first but if I get fed up I'll contact you, KLX678, to order one of yours.

Have you had any luck with yours, Adam? I'll let you know how my work goes.

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