1999 KDX220 Piston Identification

[markcr]

I just bought a 1999 KDX220 and I'd like to know if the stock piston is in it. Does anyone know how to identify a Wisco piston vs. stock? The one I pulled out has an "A" stamped on the top along with the direction arrow. On the inside of the skirt there is a maple leaf looking stamp. Does this sound familiar to anyone? Thanks!

 

[markcr]

Correction...

Correction to my previous post: the marking inside the skirt is a two-banded star with the letters "SK" stamped inside it.

 

[ridejunky]

I'm looking at my stock piston that I saved (don't know why) and it is the same, so the answer is
yes its stock (does it have a 2 stamped above the logo?)

 

[markcr]

Yep, it sure does! Hey thanks for the reply. I'll now go ahead and order a Wiseco replacement.

I picked this bike up over the weekend for a pretty good price. I knew it had some problems with the motor but wasn't sure what the problem was. When I tore down the cylinder I found that the previous owner mistakenly put the piston in backward. As soon as I pulled the head and saw that the arrow on top of the piston was pointing toward the reed valves I knew I had found the engine problem. The result was that the ring ends (when passing by the port openings) would open up slightly, resulting in a large groove being carved into the cylinder wall. :bang: I'm sending the cylinder out to have it repaired and if the piston would have been a Wiseco I probably would have kept it. However, since the stock pistons are reportedly frail, I'll go ahead and replace it with a stronger Wiseco.

Thanks again for your reply! :cool:

-Mark

 

[the trail rider]

good idea, good thing you caught the problem as it would have damaged your motor.

 

[Red_Chili]

Getting it resleeved, or bored and re-Nikasil'd?

 

[craig_enid]

Thread hijack warning!
My pulled piston has a B stamped on it. I'm just starting to cull through all the posts pulled up on my search, but I'm posting this query, anyway.
I'll assume the B is a first bore compared to the above mentioned A stamp? If that assumption is correct, what corresponding Wiseco piston would I need?
About 4 weeks until the season's first race, so no hurry....

Thanks, Craig

 

[ridejunky]

I would measure the piston to be sure. 69 is the standard size. Im not real sure what the A or B represent but once you find out what size it is, check your ring end gap on your new one with the piston near top of the cylinder and if its in specs you should be good.

 

[canyncarvr]

Pro-X pistons are grouped into alpha designations A-F. The difference is .01mm, which you likely aren't going to have a lot of luck measuring (it's less than 1/2 of one thousandth).

There isn't a 'first bore' going on. The different piston measurements are grouped with a corresponding cylinder measurement (you'll notice your cylinder is also stamped with a corresponding letter) for a proper fit. Not a big deal, for sure...but something to be aware of.

The same ring set fits all pistons.

Wiseco does not have such alpha groupings.

If you're replating, be sure to include the piston you are going to use with your cylinder when you send it off. If the plater you're using does not insist on having the piston to size the cylinder to, find another plater!

 

[KdxChode]

The previous owner must have been an idiot!!! I can see putting a piston in backwards cause you don't know what your doing....but to tear a motor down and then put the old piston back in? Why?