'A' 'B' & 'C' engine markings

[canyncarvr]

The cylinder/piston are matched sets based on these designations. The piston is stamped on the crown, the cylinder on the LH top (visible with the engine together, in the bike).

If you do a top-end job with an OEM piston, you might have a prolem.

Example: My kdx is marked 'C'. So is my riding buddy's.

BUT, if you order an OEM piston, you don't have the choice of which tolerance marking you get. You'll likely get a 'B' if you order a stock kawi 200 piston (if you have a 220, you don't WANT a stock kawi piston!). I got a 'B'.

That's a problem. You need a 'C' piston for a 'C' cylinder.

Put a 'B' piston in a 'C' cylinder,and you'll be within spec...but on the edge of the range.

My piston/cylinder clearance was .003, and the ring gap was .012. A 'C' fit would have been better.

But...I already had the parts. Don't have the time right now to wait on an EG 225..my cylinder needs to be replated anyway, so who cares if the piston isn't a perfect fit? Not me!!

And even so...it DOES run so much better!!

Wow. What a bike!!

IMO???..check your tolerance markings. If you don't have a 'B' engine, don't buy an OEM piston.

 

[KDX-Jack]

I thought you would be the person to ask............

From my understanding a KDX cylinder cannot be bored, but Weisco
sells + .010, + .020, and + .030 pistons. Am I safe to assume when doing a
top end to measure the cylinder for wear and buy a bigger piston if needed without getting it bored.

Thanks in Advance

Jack
(Always confused KDXer)

 

[r.2 stroke]

O.k then,with our cylinders being marked a,b,c,d,does wiseco make pistons in the same in the same graduations,or ,is their piston say, a 'c'??:think

 

[canyncarvr]

kdx-jack

In a word, no.

There is NO way you are going to put a .010"-over piston in any original bore. Pistons of those sizes are meant to go in a cylinder that has been bored and replated, which is to say a kdx cylinder can most certainly be bored. Of course, it then has to be replated.

r.2

Wiseco's website (pro-lite pistons) lists only oversize pistons meant for bored/replated cylinders (no 'tolerance difference' pistons). Their OEM piston would be a crap-shoot for fit in a kdx.

Pro-X is an outfit that is supposed to mfg OEM replacement pistons. From their webpage:

Pro-X piston sizes..... are available in standard sizes along with fractional increases of 0.01mm up to 0.04mm (A, B, C, D or A1, A2, A3, A4)

Note that .01mm = .00039"...call it just short of 1/2 a thousandth for rounders.


OK? Does that answer the questions? If not, feel free to ask again/summore or something. Feel free to email me if that suits you better (email in profile).

 

[r.2 stroke]

O.k Sage when you say 'a crap-shoot', do you mean wiseco will give you a piston that could be anywhere within the specified piston diameter range?(
(65.942~65.957 for the 200)
If you got a 220 like me, your kinda stuck with wiseco and whatever they give you i guess?!:uh:

 

[r.2 stroke]

Ooops! i mean't to address that reply to you Canyncarvr!

 

[canyncarvr]

crap shoot meaning..

..I don't know what you'd get. The numbers you list being .015 apart, certainly one size would NOT fit all.

Probably a piston that was within specifications, but not one that was optimally fit to your cylinder.

With the piston-to-cylinder clearance being measured in .00x, and the piston tolerances being 1/2 of ONE thousandth, there's a good bit of wiggle room.

If you prefer (as I would) to have the best possible fit for the highest return possible (moh power), putting an 'I don't know what size this is going to be..' piston into your cylinder isn't going to accomplish that.

As long as you're going to the trouble and expense of a top-end, why not do it right? ...or as right as you can, anyway. The gasket set costs just as much if you put in a sloppy fit piston as one that fits correctly. Just as much mess to cleanup, too!

I don't see a kdx220 on Pro-x's product list...but they DO say it's only a partial list, so contact them if you want to know about 220s. I'll bet they do make a piston for it.

http://www.pro-x.com/form.html

will take you to a screen that you can ask them if you wish. Also a dealer locator.

BTW, I'm not advocating pro-x as THE piston to buy. Just that they make pistons that actually FIT into different kdx cylinders. You won't get that from kawi..you won't get that from wiseco.

 

[KDX-Jack]

Awesome explaination !

Thanks Canyncarvr

JacK