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Is there a big bore kit for 94' kdx? If there is do I have to change porting carburetor etc.?

They use to take the pre 95 KDXs out to 240ccs. Problem was the engine life was cut drastically shorter if riden hard. Too much vibration is what I've been told due to the larger piston.

I have a 94

Yeah... IC said pre 95 KDX's

The E series KDX's (89-94) could be bored out to 240cc. It involves having an iron liner pressed in which really plays hell with heat transfer out of the cylinder. The jetting also has to be substantially fatter and the fuel mileage hit is around 20%. The larger piston makes the bike in to a slow reving torquer. A bigger issue is that the oversized bore comes close enough to the KIPS valves that they need to be removed to insure proper clearences. I've read reports of people keeping the valves but they all had SR models which have a slightly different cylinder configuration I believe.

Can't you 225 em?

I've never heard of it being done. I'd imagine that it would need a iron liner for that as well and would have the same related issues. I should send EG an email sometime and see if its a possiblity.

Mr. Fredette's response

Some time ago I asked Jeff about this very issue here is the email text.

"Jeff;
Is there a big bore kit available for KDX200 E-models 89-94?

steve,
there is a 240 kit some one does out there but it is not good. nothing but problems. biggest i would go on you bike for no trouble would be a 67-68 mm bore. good luck, jeff"


The piston size for a 220 is 68.95mm. I don't know if it is possible to have the cylinder bored, replated then use a 220 aftermarket piston.
Has anyone tried this???
Or maybe an oversize 200 piston?

If boring to repair a damaged cyl. I understand but for performance I think there are better things that you can do that will not hurt the life of your cyl.

I've always wondered how the 220 bore would work with 200 porting(even if it needed dressed up).