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Anybody ever use an Athena piston kit for thier KDX? Just got one in for my 2000 KDX 220. I asked for a Wiseco when I ordered it from my local shop but got an Athena delivered instead. Just wondering about the reputation for quality....and if I should exchange it for a Wiseco. I've read a lot about guys having good results with Wiseco pistons.

First... If I ordered a Wiseco, I'd expect a Wiseco.

I believe Athena makes the Bore Kits for the Thumpers....

They are great pistons, better than Weisco imo. I believe they are made by Wossner pistons. Great stuff, i have one in my ktm.

Thanks, that will put my mind at ease. I was hoping the reputation of German quality would apply to this situation.
Yeah, I know. I really did expect a Wiseco. The shop owner is a friend, always gives great service and advice so I didn't gripe when he said all of his sources were back ordered on the Wiseco pistons.....Which is why I bought from him instead of ordering online. I like to support small business, and I can give him a call if I run into a problem and need some advice.

Be sure to check you clearances....

Clearances? I know checking them is the right way to do things but I'm affraid this back yard mechanic doesn't have any micrometers. I've heard the cylinders on these bikes are tough as nails and wear very well. I was hoping to put it all together and hope for the best. Bad idea? I've got a new piston, pin, bearing, rings, circlips and cometic gasket set.

At the risk of a flame...I would primarily check the ring end-gap. Feeler guages are cheeeeep...but that is where you *could* experience a problem.

Piston (without rings) should move freely in the bore when placed/aligned properly(arrow!)....and you did say the cylinder coating is in great shape, right??

Make sure you warm the engine *properly*....meaning the cylinder is warm/hot to the touch *before* applying a boot-full of heat/pressure to the whole works. Risk is that the piston expands more than the cylinder and seizes in the bore.

Not many manufacturers ship pistons that are too big for a standard (and used) bore!

Use extreme care when installing the circlips! ie: Rag in the cases....careful fitment. if you damage the circlip or over-tweak it...GET A NEW ONE!!...they're cheap, too, relative to the damage they can cause.


Let us know!

At least make sure the box/package indicates correct piston size. And it wouldn't hurt to make sure it's about 69mm in diameter with whatever you can measure with just to make sure you don't have the wrong piston.

Check ring gap - place the rings one at a time in the cylinder about 10mm or so down and check with feeler guage(s). Wiseco recommends a minimum of 0.004" per inch of piston diameter which equates to about 0.011" for your 69.0mm piston, I don't see why the same wouldn't true for other makes. I've gotten from 0.012 to 0.016 or so when I try so it's a good thing to check.

As you reassemble, before you bolt on the lid cycle it through a stroke or two just to see. hear, and feel that things seem fine.

Gee whiz, I posted right after GS - same story though!!

Thanks for the tips! I do have a set of feeler guages so I should be able to check the ring end gap. If the gap is too big the cylinder is worn out?

That coating doesn't wear much. Look for grooves and or flaking. SO, an excess end gap wouldn't be a cause for concern to me (within reason) but, TOO SMALL an end gap means you're soon to experience a broken ring.

I bet it's within spec, but you do need to ck, cause the damage is BIG-TIME BAD!

Just one add to Jeb's comments.....use the piston crown(top) to level the ring in the cylinder. And remove and place it with great care, so as not to damage.

rdsrf wrote: . . . If the gap is too big the cylinder is worn out?

A BTW: the gap is checked to ensure that there's enough clearance between the ends when the ring is compressed in the cylinder, not to "gauge" cylinder wear

Thanks again for the info. I have a better understanding of the reasoning as well as the procedure now. I think I'll rub a bit of oil in the cylinder while placing the ring in to check the gap. A little extra insurance to avoid damage to the bore.

Oil in the cylinder is a VERY good thing to do. And standard practice for anyone I know.

Don't forget to ck to see if the end gap measurement is within required specs, as the gap will close up when things get HOT in there...

Just a quick note! You should also check the piston pin hole to the the top of the piston (Compair it to your stock KDX piston). I have both seen and heard that the pistons that Athena supplies have up to .020" differend deck heigth.

Ron

Is the difference in deck height cause for concern? Too much or too little compression? Interferance with the head? I don't think I have anything that will measure .020". I doubt the naked eye can tell the difference. So the Athena pistons are not known to be precision parts?

Yikes. That would be a pretty big difference in height.

Lacking a suitable measuring device...perhaps setting them up beside each other will point out any obvious difference and .020 is quite visible with a background reference point for your eye.

Bit crude, I know, but sometimes you can still get a clear idea, using a little ingenuity. If there is that great of a difference, then you better not just throw it together.

I think Ron really knows what he's talking about here.

Oh boy. This is getting a little too complicated and risky. Maybe I should see about exchanging for a Wiseco.

You should do these checks no matter what piston you stick in there. It's just a surety that you have the right parts and that they fit YOUR cylinder.

Don't worry, it's not complicated or anything. After the first time measuring, you will be the expert.