Weisco VS. Pro X

[clutchcover]

Well, I am rebuilding the topend on my kdx again. Last time I used a pro x, and all was good, but this time I got a good deal on a weisco. I am just curious what advantages either piston has over the other in the kdx. I've used both types in other bikes but never in my kdx. Just wanting to get some fellow riders opinions.

[KDXer]

I think its the manufacturing process differences that are the big factor (piston material, etc). Someone else will have to give more details as thats all I remeber. CC has told me the differences before I'm sure he can help here.

[canyncarvr]

Largely it is a matter of opinion.

And mine is right a good 20% of the time...so here 'ya go!!

In the case of the 220 Pro-X piston, (OK..piston from Pro-X..not MADE by Pro-X but distributed by them) it has known problems. Don't put a Pro-X in a 220.

You don't have a 220.

One of the advantages of a Pro-X is being able to 'size' the piston to your bore. If you have an 'A' marked cylinder/piston, you should (everything else being ok) use an 'A' piston.

The difference between the letter designations being a bit less than 1/2 of one thousandth of an inch (.01mm), it's not a huge deal. But...if you're buying a piston, why not buy one that fits?

If you order from Kawi..you cannot specify which alpha designation you get. You will most likely get a 'B' piston.

The rings are the same for the different letter designations. That kind of gives you an idea of how big a difference it makes...not a whole lot.

Your best bet is to have your cylinder measured and choose the Pro-X that gives you the best fit. That will allow for finding out your cylinder is worn out of taper-spec. Not real likely with a plated cylinder and no visible damage...but it's easier to check when it's off the bike than when you're riding.

Wiseco's (Y-Z-Khos? ;) ) are forged aluminum. Not cast. Generally a Wiseco piston needs to be fitted a bit more loose because of that. The forged piston and cast cylinder expand at different rates. That's where the nickname 'Seize-co' came from for Wiseco. If you setup your top end too tight for a forged piston, it's more likely to stick.

That's not the piston's fault. It's the builder's fault.

The whole 'setup' issue applies to a cylinder that is not plated...being bored or finish honed...or a plated cylinder that is being REplated. On your regular one-each plated KDX cylinder, you don't change the bore size to 'setup' the fit of the cylinder to the piston.

When my cylinder was replated..the piston was supplied so the plater could do the 'fit' TO the piston of my choice (a 'B' Pro-X).

Wiseco's come in only one size for a 'standard' bore KDX. There are no alpha designations to choose from.

Wiseco did have a problem a couple years back with providing piston pins that were a bit too long. The pin clips didn't 's-n-a-p' into place as they should...they'd come out. Not a good thing.

Make sure your clips SNAP into place. Make sure the clip gap is installed as specified.

...don't argue the 'it doesn't matter' part. You would be wrong.

..IMO and all that....

[fuzzy]

Yeah, Like CC said....

One's cast and one's forged(Wiseco). Forged pistons are better for high-rpm applications, NOS, boost(turbo/supercharging), high compression w/ racing fuel/alky, etc. Not much of this going on w/ a KDX motor. If you use a Wiseco, just make sure the motor is at full operating temp before flogging it to avoid cold siesure('Sticking')....

[clutchcover]

Thanks for the info. Will keep all in mind. Cylinder is a "b" and at last tear down was well within spec. I'm one of those you can't be too careful types and am pretty anal about maintenance. Tear down begins Monday (hopefully) and my annual grease everything- a- thon begins. Thanks to all for the help.