I have a 2007 KLX250 with 9.5K miles. I have had it for just over a year and I decided to check the valve clearances. I had to correct 3 of the valves, so the bike sat tore down for a couple weeks waiting for new shims. I got the valve clearances all set within spec and got things timed up and put back together. The bike only started after much cranking and wouldn't idle or run faster than 3K RPM. It sounded awful as well. So after work today, I tore back into it and found what I suspected last night...a previous owner had modified the cam timing.
New owner tip! Before you tear into your cam train, check the cam timing setup. If its not stock, take a photo at TDC.
It does not have what I read is called the Marcelino mod, since only the exhaust cam sprocket has been moved.
Does anyone have any advice on how to proceed? I can certainly go back to stock, now that I see what has done. I can proceed with full Marcelino or try to replicate the timing prior to clearance adjustment. I am concerned that the compression release, since I am not sure whether its in the stock position or if it was moved when the cam sprocket was moved. I do know the bike generally cranked over and started well last year.
Thanks in advance.

 

Firstly, you have a moron for a previous owner. This little disaster may not be the only surprise you find with this bike...

The '06 and '07 KLX's may not benefit from the MCM as much as the newer KLX's - this is due to the older cams, apparently, being different from the newer cams...

IMO, put the cam timings back to stock and simply pull the spring off the KACR (if it hasn't already been pulled off - and likely lost..)...

 

Yeah, this bike has been messed with. I have found plenty of things that needed fixing.
Thanks for the input on the MCM. I didn't realize it was of most benefit on the newer KLX's. Since the exhaust cam was already moved and the bike started well, I think I may try the MCM timing. I am getting good at tearing into the top end now...
You got me thinking about it now though...

 

What am I missing here? It ran good previous to you changing the shims on 3 of the valves. And now you think that the previous owner messed up the cam timing?

Ride on
Brewster

 

Ahhh, yea.... If you changed the shims, YOU changed the timing! (unless you had all the locations marked, but you left it tore apart weeks, I would have forgot what I did)

 

After changing the shims, I timed the bike per stock settings. I didn't notice that a previous person had moved the exhaust cam sprocket to the intake mounting holes.
So this put the exhaust cam way off.
So yes, I changed the timing when I aligned the timing marks like the manual says too....
I should have looked at the cam timing before I took it apart. Hind sight is 20/20 as they say.....

 

Well just make sure you get the MCM right - this might be quite a project if the exhaust timing is screwed up - you may need to return everything to stock before attempting the MCM - KLX678 has the pics and instructions on his signature line.. Note: the cam chain movement is right to left when you are looking at your pic above..

If the PO did the exhaust cam right, it is retarded 1/2 tooth from stock. The KACR has very likely been repositioned or its' spring has been removed.. You should know that doing only the exhaust cam has never been a "thing" nor has it ever been a recommendation - never has it been verified as a performance adder.. The only thing I have ever seen about "exhaust cam only" was a horribly flawed youtube video that tried to get peeps to change only the bolt holes ( from EX to IN) - leaving out KACR issues and the 2 chain link final readjustment..

 

Thanks. I saw that video last night when I was researching popular cam timing mods.
I downloaded his instructions and set the timing per his instructions and photos. I am pretty sure I got it right. I got the bike back together enough to try starting and it fired right up. There's pretty severe off idle stumble now, even after warming up. It didn't exhibit that before.
I am leaning toward taking your initial advice and switching back to stock timing completely.

 

Post for link in signature. Regardless of what you do with the cam timing, take off the KACR to disable the compression release. It was unnecessary to start with. My bike spun over just fine at 3 degrees F without the compression release.

I won't say the MCM will work, won't say it won't, but will say it's worth a try and do both intake and exhaust.

 

Since there is zero chance a properly done MCM causes any kind of running or operational issues, you'll be wasting time and effort blaming it for such.. MCM is not experimental. And many '06,'07 owners are very happy with MCM results. We just do not have dyno data proving the same effectiveness on the older bikes as we do the newer bikes..

Your current issue sounds like a CVK fault, fuel delivery fault, a vacuum leak somewhere in the induction system, etc etc...

The increase in low RPM power does increase the "workload" on the CVK - while it has never occurred/been reported, I've always thought an iffy carb, or carb setup, might be pushed over the edge by the MCM..