So I've picked up a 2007 KLX250, its my first Kawasaki(been a Yamaha guy), so I'm asking all the KLX guru's:
What should I be looking out for/replacing on this bike?
I plan on doing a full carb rebuild, oil change, coolant swap, and brake service.

 

Look for cam drive noise. The KLX, among others, is known for the automatic tensioner to fail. I know, I have one and having a member here work with me I made a manual tensioner that many members here are using. That seems to be the main point of failure. The carb on all the U.S. model KLX250s was jetted lean, performance gains from simple jetting definitely adds power.

The noise is usually noticeable in the 4000-6000 rpm range initially. It will get worse and may eventually be audible over pretty much all the rpm range. Replacing with another OEM tensioner is both expensive and likely futile. I had two of the same design tensioner fail in my KLX650 in less than 14,,000 miles. It was the first bike I made a manual tensioner for, I did again with my Zephyr 550 and ended up doing a bit of a cottage industry making the tensioners for numerous models of Kaws, Hondas, Suzukis, and Yamahas. Biggest seller was for the KLX250, next now is the WR250 and CRF250. Similar design tensioners that fail.

So if you hear rattle or clatter on the right side in the cam drive it is the tensioner. Otherwise the rest of the KLX is pretty much bullet proof. My 2009 has been as has my brother's 2006.

Here is a site that has the specs for the carb jetting using Kawasaki parts, not to mention a lot of other good information. D. Pippin's KLX250 page - click here. If you want to use Kaw parts he has the parts numbers listed. There are numerous posts here about jetting with KLXster doing a lot of work using the Dyno Jet kits. I did the Kaw stuff and it was pretty much plug and play. It may not product max power, but it worked well without a lot of goofing around.

I forgot to mention, a new OEM tensioner is over $70 usd, the manual one I make is $39 plus shipping and I do world wide sales. PM me or if you want you can use ebay finding my listing there, but paying a bit more due to fees.

 

That is some excellent info! I'll be sure to replace it with a manual one regardless.

I've got a low compression issue so I'm going to look into that too. This bike sat a while so hoping its either stuck rings or build up on the valves.

 

I think you may know this, but the KLX does have a compression release on both kick and electric start. I don't know how that will affect the compression check. On the electric start the compression release is really not needed. I have mine disabled. I may have it pressed out of the exhaust cam sometime. It can be disabled by removing the spring on the shoes, too. Make sure that isn't affecting your readings.

 

Yeah. The previous owner told me his mechanic said "the valve is at 6 when it should be 13" whatever that means. So I'm going to pull the valve cover and check clearances.

 

Alright good news!

Engine is in fantastic shape, the valvetrain is clean and basically has no wear. Its possible no one has ever been in this engine as there are no timing marks on the cam chain.
The spark plug is black, as is the combustion chamber so I think this thing has been running really rich. I'm tearing the carb down now to see what jetting it has.
I'm hoping its carbon build up on the valve seats causing low compression. I couldnt find my feeler guage so I have a new one on order to check the clearances.
Cam chain tensioner also looks basically brand new.

EDIT: Carb has a dynojet kit in it, and is so clean I could eat off of it. 132 main jet, 35 pilot jet.

 

Okay so, exhaust valves are 0.15 and 0.17. Intake I can't even measure, my gauge only goes to .12. So that could be the problem, would make sense if the mechanic said it's at "0.06" when it should be at "0.13". Going to get another feeler gauge and check again but looks like I need to order some shims!

 

FWIW, there is no reason to mark the cam chain, how the chain fits up is really irrelevant. It's the marks, the fly wheel mark for TDC must line up with the notch in the timing hole of the left side case and the marks on the cam sprockets must line up with the head parallel to the head surface, per the manual. Only change is if one does the Marcelino cam timing modification. There is no real value to marking the chain.

Some people may mark the chain as a short cut. I didn't bother. I fitted the sprockets so the timing marks lined up when the chain is tight on the front run (any slack in the back). I don't know if there is enough space at the crank sprocket for the chain to skip a tooth or so, so I didn't do any short cuts and wouldn't recommend them. Just make sure the marks mentioned above line up where they should when they should.


For the carb go search for some of the dyno jet threads and posts made by KLXster. He knows his stuff with the dyno jet setups.

 

Yeah I thought about that after posting haha. Shim kit will be here tomorrow. I will hopefully have it running by the afternoon.

 

That's understandable. I've read some places where riders zip tied the chain and sprockets. Problem there is if the chain should move on the crank shaft sprocket. So it's best just to ignore the chain and go with timing marks. One thing to be sure, when you get the cams set, but before you put the cam cap on and put the cam chain tensioner back in place, check. You get it all in, then using your hand on the sprocket, rotate counterclockwise, pulling slack out of the front of the drive. It won't move much, after all, you're just using your hand and the goal is to just take out any loose slack. At that point the marks on the cams should be parallel to the head surface looking in from the side. If you made a mistake and are on a wrong tooth it will definitely be obvious. It took me four tries, I just kept moving one tooth too far or in the wrong direction, but I finally got it right - marks were where they should be.

At that point I carefully put the cam cap on, torqued it down per the manual, the put on the cam cover, torqued it too - small fasteners easily overtightened. Put in the cam chain tensioner and it's buttoned up. If you have a manual tensioner it can be adjusted at that time. If you have a manual tensioner, but no instructions let me know. I can send a link to my directions I send with my tensioners. If using the OEM tensioner, put in the spring and cap, it will push forward. But if using the OEM tensioner be aware if it is failing. The indication of the tensioner going bad is if there is a buzzing in the mid range, between 4000-6000 rpm and on deceleration. If you find it is bad or does eventually fail, PM me. I developed and sell the KLX250/300 tensioner with help from a couple riders in this forum. It's a well known item and does solve tensioner issues.