One little trick is, when you pull the cylinder off, immediately stuff the exposed crankshaft opening with clean, new rags. This will prevent anything, like the piston pin retainer clips from going BOING when you go to install them, from falling inside your engine. Anything solid falling in that opening will more than likely mean pulling the engine and splitting the cases, IE a complete engine tear down, to retrieve the object. Although, I have seen a guy pull the engine and flush with carb cleaner, Miracle oil, WD-40, shake the engine up side down for an hour, use an air nozzle, LOL. Still heard the crap rattling around in there...And that engine smoked like a diesel for miles and miles after he fixed it and rode it!!

Maybe you mistyped your question about the 250 piston; you cannot reuse it with any bore change...one would have to put in a different rod, with a different length and "stroke" the engine to re-use the 250 piston and it's original bore diameter. A big bore kit by definition enlarges the piston diameter required.

 

Horizonod: If you scan the thread you'll see that 4 posts above yours, I totalled everything up to do a 300 kit via buying a KLX-300 jug and parts from Ron Ayers, and it came up to ~$478. I'm not exactly Mr. Big myself so I seriously doubt I ever have the money for that. I'll do exhaust before I do that.

 

I am in the process of doing the 300cc upgrade. you buy the klx300 jug, piston, pin, clips for the pin and gasket set.

Your old 250cc jug and piston and pin get removed. you bolt on the new 300cc stuff. instant 50cc upgrade.

it uses all kawi parts and no boreing is required. it is also the most expensive option.

Reliability is subject to comparison.It is just easier to get the 300cc parts as you go to your dealer or bikebandit.com or whever they sell oem kawi parts and buy it.

Bill Blue is very knowledgable and very helpfull. the only issue I had was he only accepts money orders or checks. i wish had the 500.00 in Cash. However, I dont so I went the 300cc route.

If he had accepted paypal pr credit card it would have been different.

 

I can't see getting a 300 cc kit from kawi when more CC's are less money. Parts shouldn't really be a concern because all of the other engine parts are the same. If you need "new parts" on a bored out jug there are only a few that are different. If you need to replace the piston or jug you get it from wherever you got the bored jug n piston. Besides, you can always put a 300 kit back on if the bigger bore pukes.

The 300 kit is also most expensive seeing as you are buying a completely new cylinder rather than trading your existing cylinder, and some cash, for your stock one.

Where do you get a 340 kit? How does the 340 kit compare dollar wise to the 351? How much dollar difference between the 331 and the 351?

 

The search function will probably get you some threads that can provide a lot of information on the different sized kits.

 

thumper racing sells the 340 kit. I tried talking to them about buying one. they gave me a price quote and then ignored me on all future emails.

If you have cash buy the BB setup. If you have credit, buy the 300cc jug or same your cash until you can afford the bill blue setup.

 

Bill you had me at 340, stole my heart at 351 if you made a 450 bore kit, I'd sell my left nut... First you'd have to start with a complete new head hotseatpreformance, made a 600 cc kit for a polaris predator cnc machined from a solid piece . If you think you can do that I'll wait. The hp and high reving power would be nuts, and a large duration short lift cam. I've got to stop or I'll not sleep.

Here a picture of there kit.

 

The suzuki Drz 400 bore is 90 mm and stroke is 62.6 mm for a total of 398 cc
The Kawas klx 250 bore is 72 mm and stroke of 61.2 mm for a total of 249 cc
Bills 351 bore is 85.5 mm and stroke of 61.2
If the 90mm bore was install 389cc's

I found a langston racing drz 450 big bore kit and said it could make up to 51 hp. which punches the 400 out to 95.7 mm bore.


I agree with Bill. We could go 450 now who's going to do it. Only .6 mm different in stroke.
the klx would need a bore of 96.8 mm.

Bill do you think you could use a stock 90mm piston(or modified) from a drz 400 to make us a 389 cc.

 

The problem with your theory is limited space for sleeve and the water jackets not enough space.

 

It's not much more .5mm of metal. I know it raises overheat issues. I've been looking at the drz 400 cylinder it has a larger coolant area. I wish I'd cnc equipement I'd cook one out tonight and would not sleep til I got it...