I'm posting this over here, because best as I can tell, merickk who posts over on the ADV forum doesn't post here...if he does, I just missed it. He was on a CO trip in the Silverton/Ouray area when got a crack in his 351 cylinder. He's still trying to make his way back home with his bike, so he hasn't had a full diagnostic session with it yet. He did post up this pic of his cylinder which he field diagnoses as a crack about midway up the cylinder that runs in the circumferance of bore. He said all his coolant boiled out, but he can't yet tell if the boilover preceded the crack or vice-versa. I'm not posting this as anything but what it is...a cracked cylinder for which a complete diagnosis hasn't been made yet. I just thought it appeared to be an odd crack and of interest to those of us who own KLX's.

 

Rot-row! I'm interested to hear more on this one. thanks for the cross post TNC Sounds like it's going to wreck his trip.
Dan

 

Dang, that's peculiar.

 

Can't tell from the pic - wonder if that crack is coincident with the top of the crankcase deck?

 

Ya mean like "I forgot the dowel pins" ?

Any time I saw a sleeve crack it was the other way.

David

 

Hmm. Crappy. I wonder how this will turn out.

 

Wow. Gonna watch the outcome of this one.

The 350 kit on our bike produced a fine spray of coolant underneath the rear fender under heavy abuse. Couldn't find the problem but installed a 1.8 bar radiator cap just in case. Took the bikes out to 100+* heat (Plaster City) and didn't have any further problems...

 

FWIW the crack in my KK330 was vertical and I do belive the crack proceded the boiling out. I was stuck in uphill bumper to fender trafic. I felt the fan come on and off a couple times then the fan came on and the high temp light came on not long after. Totaly different animal since it was bored and plated not bored and sleaved.
Jim

 

That's prolly why none of the big bore kits sold here in Japan go past 315cc.

With the KK kit though, I think the extra heat generated by the higher compression ratio is a major contributor. It's somewhere in the 12:?:1 range, (maybe 12 and a halfish) don't remember the exact figure, but Marvin has it handy.

The 351 piston design keeps the CR near stock, but the sleeve intudes into the water jacket, and it won't cool as effeciently as the plated kit.

I heard someone mention '350' though.... would that be the one put out by Thumber Racing, or did they mean '351?'

I'm plenty happy with just the KLX300R cylinder (and Wiseco piston ), but to each his own.

 

Well, we still don't know the real reason. However, being that I ride 100% in the desert, that's why I went with the 331...it was the largest Dry Sleeve offered. I just didn't want to push it to the largest offered. That said, whether it's wet or dry may not make a difference, and we still don't know what the real reason is for this problem.