Just my opinion,

The original poster said he had a hot engine. He did not say if it got hot and then took a crap or if took a crap and got hot. This matters to me.

It got the heat test and failed the way I see it. Nothing should be expected to pass the heat test. A cracked sleeve is not that un common in the old days.

If the engine over heated and the sleeve cracked as a result, its no ones fault. Just a result of riding in too much heat.

David

 

a. tropical heat had nothing to do with it, i can guarantee that. ive rode in the desert in triple digit heat and never had a problem related to heat. this bike was designed when water cooled four strokes where new, and kawi majorly over designed the cooling system (in my eyes, and definally not saying its a bad thing). compare the klx's 2 radiators to the wr's 1. the bubbling in the rad tank was probably the exhuast being pressed threw the crack and finding a new way out.
b. it has to be from the thin walls and higher compression and time. like its been said, these really are dirt bikes (klx300). with that said, this was a kit designed for the dirt bike, and used on a dual sport. in that train of though, 10K in a lot to get out of a motor. hell, if it was a ktm 250, people would be wondering wtf you did to make it last that long. i see the bb kit as more of a dual sport kit, and would expect atleast 10K on that. people have a fair number of miles on there kits.
c. I wAnT PicTUrEs!!1!1!

 

I don't know. I'm not sure I agree with the 10K mileage being that great with heat or otherwise. My '06 had 11K when I did the 300 cylinder, and the piston, rings, and cylinder looked in perfect condition. Our heat from April to September can get to 100 or more with no problems, and the June-August heat is regularly 95-105F. As punken stated, these are watercooled bikes and don't suffer like air-cooled models. I had 4 XR250R's, and they looked quite rough in the cylinder and piston wear at well less than 10K. I ride my KLX300S about as hard as any of my XR's. I have a digital inline water temp guage on my KLX, and it has amazing temp control.

My guess is that there was just a failure due to a bore issue, maybe some porosity in the original 300 cylinder, or any number of those tiny glitches that can cause a problem. Who knows. Until some pattern of this develops on those plated cylinders, it probably has to be written off as "stuff happens".

 

Stupid newbie question. Will the OEM KLX300 cylinder bolt right on to the '09 engine? Is that what the KK kit is, an OEM 300 cylinder bored over and plated? If so, how far over is it bored?

My friend just did an air-cooled airplane engine in Nikasil. He thinks it's the cat's pajamas. I have another friend who has 50,000 miles on his Triumph Sprint ST that has aluminum cylinders with Nikasil plated bores. I don't think there's anything wrong with it except it *****-out expensive. I was told you can go with a tighter clearance between the piston and cylinder, since they're made with the same materials, making them expand the same, and it'll transfer heat better.

 

10k on a big bore kit seems ok to me, but sorry for your problems. But I would look into why it over heated 1st that may have caused the problem.

My old klx with a 331 kit NEVER came close to over heating. Even running a muddy enduro on a 95 degree day.

My stupid ktm is an other story. It can over heat at a traffic light on a 80 degree day. And it just lost the piston at 177 hours.( 4000 miles) ktm piston - $365.00 I miss my klx.

 

I doubt the Nikasil is the problem, many engines use ally cylinders.
KK 330 kit is an overbored 300 cylinder, and yes it fits the 250 bottom end.
300cc is 78mm piston, 330 is 83mm.

 

That's bored .197" over. That's a little much. That thing is not designed for that. Granted, it did last 10,000 miles at highway speeds. That 300 jug must be bomb-proof if left alone then.

 

Will all years fit? I'm looking just for kicks because I'm bored. I want to see if I can get a picture of the top.

Does it use the standard 300 head gasket?

 

Well that blows...Like I always say, if it's not broke don't fix it....but since it is broke then go ahead.

 

FD, if you're asking about the fitment of the 300 cylinder on the 250, I do know that all years of 300 cylinders will fit the '06 and later KLX250's. There is a point, however, going back in the 250 lineup where the case opening for the cylinder is too small to accept the 300 cylinder. I don't think I've ever heard what year model that ended at.