Afewweeks ago, I got a KLX300 cylinder and piston from mmatz. It was in excellent shape and could have been run as-is, but I figured if I'm going to do this, let's go all the way. Nobrakes and others on this forum have gone the 331cc route with Kustom Kraft. KK bores the stock 300 cylinder, then recoats the bore with Nikasil. Partly to be different, and partly because Iwanted the 9 extra cc's, I decided to go with a 340cc kit from Thumper Racing. TR doesn't bore the stock cylinder oversize, but instead reams the cylinder out to the water jackets, then installs a steel sleeve from L.A. Sleeve. I sent the cylinder out to them in Texas about a week-and-a-half ago, and when I got home last night, there it was. Since I couldn't find any good pics of this kit, and I know others might be interested in it, I thought I'd share some pics of my kit. I'm a virgin at posting pictures this way, so I hope it works.





The kit includes a new piston, rings, wrist pin and circlips, all the needed gaskets, and my resleeved cylinder. It also includes new heavy duty clutch springs, but I forgot to take pictures of them. [:@] The clutch springs are the reason they also include the right-side case gasket.





This is the newly-sleeved cylinder. You can see the sleeve goes all the way out to the water jackets. If your worried about rust, don't be. This setup is really no different than a cast iron V8 block. You can also see the cross-hatch in the bore. Thumper Racing not only bores and hones the cylinder, they also hone to match the piston. Since there are production variances in pistons, they measure the piston, then hone the bore to match so that the piston-to-wall clearance is exact.




Here's to bottom of the cylinder. You can see how much the sleeve tapers from topto bottom.




The piston is custom made for Thumper Racing by Wiseco. If you were wondering which exact piston is used, here it is.




On the left is the new, forged 340cc piston. On the right is the stock, cast, 300cc piston. The stock piston measures 78mm in diameter, while the new piston is 83.95mm - a difference of nearly a 1/4". It is hard to tell that in the picture though, since the new piston doesn't have rings installed yet, while the stock piston does.




Here's the bottom of the pistons. You can see how much beefier the 340 piston is.

Well, that's my kit. Total cost with shipping was $483 for the entire kit. That doesn't include the original cost of the cylinder. I can't wait to install it, but I'm waiting on a Bill Blue carb and my exhaust. Once all the goodies get here, I'll tear into it. The only thing that has me concerned is that they media-blasted the cylinder before sleeving - both inside and out. I don't want to bolt it on that way because it will turn that milky white color as it oxidizes. Does anyone know of an enginepaint that matches the silver on our engines?

 

Mike, can't help you with your questions, but that sure is a purdy kit.

 

Thumper....that's funny.........I guess only to me it appears

 

I think their logo is cool...

 

Actually 78 mm is the stock size of the KLX300. The KLX250 uses 72mm so the difference is even larger, nearly 12mm for, 11mm for the 331cc kit which equates to almost 1/2 inch larger bore size. Quite and increase, 82cc for the 331cc or 91cc for the 340. That's like a whole other extra bike's worth of power.

 

I don't know what paint color matches but I would check into what it would take to clear coat it. It should maintain it's look that way.

 

You're right Brian, and I forgot to mention that.

BTW, when you had your cylinder done by Kustom Kraft, did they paint the outside, sandblast it, or what? Thumper Racing media blasted the paint off of the outside of mine. That's fine, I guess, but I don't want to put it back on bare - it will go off-road and it will get wet, so it will corrode. I have some satin clear that's good for 300 degrees, but I don't know if the outside of the cylinder gets hotter than that.

 

Awesome, can't wait to hear how it works...you should notice a small increase there lol

 

Don't know about paint to match but I think it would look sweet with the Jug painted gloss/semi-gloss black, it would be "different"

 

Aside from cleaning it real good with PJ-1 contact cleaner, I didn't do anything special with mine. They said it was ready to bolt on, so that's what I did.