Hello everyone, per usual I really try to solve my own problems via extensively searching the web and troubleshooting but alas I am at a point where I need some help.

I recently purchased a 2006 klx250 that hasn’t been run in a few years (garage kept indoors). Before diving too deep down the rabbit hole of ordering parts I wanted to make sure it ran, so i removed and cleaned the carb, air filter, and charged the battery. She fired right up and I spent maybe 25 minutes ripping around the yard feeling it out. Everything felt normal and strong.


I pulled off the valve cover to check the clearances and noticed that at TDC the timing marks on the cam gears do not align with the cylinder head/valve cover mating surface. It is my understanding that these marks should be parallel to the gasket surface (within reason) if it’s timed correctly. However, the exhaust cam in particular seems to be off by a tooth. (I count 31 pins between gears, the service manual calls for 32)


Is this engine timed wrong? Like I said, it ran and rode really well, and I don’t think any of the previous owners ever opened up the engine. I’m pretty confused tbh.

I scribed the gears as a reference so I can put it back but I’d prefer to understand if this is right or wrong. I’m a big fan of “if it’s not broke don’t fix it” but I also don’t like finding discrepancies between the real world and the service manual.

I also quadruple verified that the engine was at TDC on the compression stroke and used a straw to visually verify TDC. All valves measured in spec and the T on the flywheel is aligned in the timing viewport.

Thanks in advance for your insights.



(I also have a 2001 klx300 that I’ve rebuilt so I have some previous exposure and familiarly with this engine)

((also ignore the ugly JB weld band-aid fix, I bought the bike like that and have a replacement cylinder head I’ll swap eventually. The damage is purely cosmetic))

 

If they have JBWeld all over the cylinder, I'm a go'in to assume it has been opened up. They probably did it wrong or tried to do the MC Mod that is here, it messes with the cams. I would look at that thread to make sure what it is, but I would put those cams back in line. It wouldn't change the running that much off only one cog, unless you were in a race.

 

Durielk thanks for the reply,

I spent some time reading about the Marcelino mod, however I don’t think that’s the situation here (both bolts are in their respective original holes on the gears). I agree that there are strong chances it could have been apart before so it’s reasonable to assume it was most likely reinstalled incorrectly.

So basically you’re saying that even if the timing was off a tooth the engine could still run and appear to be reasonably normal? I think judging by the picture that the exhaust had been retarded by one tooth (correct me if I’m wrong). What sort of characteristics would this theoretically yield? Before I fix it I just want to make sure this was a mistake and not some other mod that I haven’t read about thus far.

The deeper concepts to all the cam advance/retard/degree possibilities are still somewhat new to me.

thanks a bunch in advance

 

Cams are available in many different timings. From 10000rpm racing engines to 2000rpm tractor motors. As long as the valve doesn't hit the piston, the engine will run.
I don't know if on a KLX if a valve would hit the piston for sure, with the high level of output, I'm thinking it could. But retarding the cam would increase this possiblity, advancing the cam would not. With the piston coming up on the exhaust stroke, think about it.
I've been around here for years, no post that I have ever seen other than the Marcelino mod even discussed moving the cams. I didn't do that mod cause it was for lower rpm, 250cc size.

 

OP, just set up the cams back to stock and verify all is good. Then do the MCM if you want. Did that bike break a cam chain? Why the epoxy on the head? If it did break a chain you need to take a serious look at the cam chain tensioner if it still is running an OEM auto adjusting one. They go bad frequently, as many here can attest to. With the help of another rider here, I developed a manual tensioner which solved the problem for a whole lot of KLX riders, eventually including myself and my brother when we both picked up KLX250s. If you don't have one I think many will suggest you do install one. If you have one and need instructions on adjustment message me. I can get them to you.

The MCM is not just boosting low rpm power, but the whole range and not just for a 250. It seems cam timing like the MCM shows up elsewhere. That was Marcelino's original point was, the optimum historic cam Lobe Separation Angle (LSA) for four stroke engines was what set him looking at the cam timing. I remembered another article where Joe Minton did similar work trying to attain similar cam LSA in a Nighthawk S.

After reading about cams and timing in Hod Rod the MCM is boosting the entire range of the KLX, just peaking earlier, but higher power. It narrows the cam LSA similar to the narrowing done in this Hot Rod tech article click here. This article compared three identical grinds except the LSA in a small block Chevy, The narrow LSA, which, according to the article, is boosting the lower range, but if you look at their charts, it actually boosts the whole power range.

The MCM is doing the same, but where most of us ride, from around 3500 up, peaking with more horsepower although maybe a few hundred rpm lower than the wider LSA will. So you feel more power down low, but notice the power peaks a bit earlier. The point in Marcelino's article was the power delivery and peak power, not that it revved higher making that power.

 

I believe the bike was dumped/crashed on the right side and the cylinder head got cracked and started leaking oil, however I don’t know the back story so I’m only speculating from what I’ve found so far while digging. Nothing internal is damaged so far but I’ll definitely double check the tension as you’ve mentioned.

Thanks again all for the replies, I think my game plan is to set it back to factory settings and get it completely operational again. Once all the quirks have been found and handled I may look deeper in to the MCM.

 

Was the head damaged too? If so, that is classic cam chain snappo!
Cylinder heads don't get cracked in a dump unless the frame is bent, muffler is smashed, and ... some one .....
Please tell us the real tale!

 

Like I said, I don’t know the story I just bought the bike last week, I can only guess based on what I’m seeing. No damage to exhaust or frame, just some small cracks on the exterior of the cylinder head casting where the timing chain cavity is. If it had to crack anywhere that’s probably the best place it could have, because essentially it’s just a shell right there protecting the chain.

I have another head so it doesn’t really matter, my main concern was the timing. I wasn’t sure if it had been set up like that purposely for some reason unbeknownst to me.

I definitely appreciate the replies and info though.

On a side note, has anyone had any experience putting new valves into a used head. Did you just lap the new valves into the existing valve seats assuming their in good condition or is it best to have a complete “valve job” done aka recutting the valve seats and whatever else that entails.

 

I did valves in my old SR500. If I remember right we put some marker on the seats to see how they seated after doing them. Wasn't a hard job, not like some special three or five angle cut or anything. I think we may have cut the seat on the intake, which had dropped (reason for the work). That was about 35 years ago so it's kinda fuzzy.

I'd say if the seats look good I'd put some marker or Dychem bluing on the seats, then work the valves with some lapping compound and see what the seats look like. If all is good then do it. Otherwise cut the seats. Why do what you don't need when it's easy to check.