I posted this in the wrong section earlier, so here it is again:

Is there any appreciable difference in quality between the three?  There is a considerable price difference.  I used Vertex with great results in my 2 strokes.

Procircuit is just rebranded Je Pistons.. I would say get a CP or JE piston..

Pr1malR8gw, on 14 May 2012 - 10:28 AM, said:

Why?  I'm looking for some product reviews that point to value.  PC just has a hot name behind it.  Vertex is largely unknown.  But is their product any worse?  I know they are a HUGE manufacturer.

Well, without much input, I split the difference and ordered the wiseco kit.

I put a Wiseco in my 07 and it got horribly loud. The clearance was dead on. It worked fine though.

A piston made it loud???

Paab, on 15 May 2012 - 10:58 AM, said:

The engine got noisy, even though piston - cylinder clearance was good. Others have had this happen too.

As in like rattley?

Paab, on 16 May 2012 - 05:39 AM, said:

Yeah, sort of rattley/whirring/ringing.

My buddy had the exact  same type of bike and changed his piston for a JE and the sound was the same as before he changed it. Everyone heard that my engine was noisier.

Edited by D-K, 16 May 2012 - 11:14 AM.

Ah, gotcha.  I think my bike may have a wiseco in it now.  It has always had a lot mechanical noise.  I always wondered about that.

I would say cp is the best, wossiner (sp?) is also VERY good,  i know people say wiseco are good but i just don't trust them.  I would choose from cp, wossiner, and oem/prox

So, I finally did the top end.  The piston in there was indeed a wiseco hi comp and it looked mint after 2 seasons (I'd guess 80 hours) plus some unkown amount of hours.  The cam chain was stretched  out pretty badly though.

After replacing both, the bike runs great and is quieter with the new cam chain.  I still get a lot of popping on decel, but I guess that's from running pump gas on the hi comp set up.  There was no visible signs of any detonation on the piston ring land, so I'm not gonna worry about that anymore.

I'm happy with my choice.

What year is your KX? If it is fuel injected there should be zero reasons why it would pop. If it isnt then I would work on the jetting and you should be able to get it right, if you are running premium (91) you also shouldnt have any problems. I know that procircuit (JE) claims that pump gas is fine, so im not sure why wiseco would be differant. I would invest in a jet kit and then you should be set. (once you figure out the settings)

Well,  It's an 09.  I have gone richer on the pilot. (45) and it makes no difference.  Perhaps I should raise the needle a position.  I don't think the main effects this at all, and I'm not so sure the needle does either.  Pretty sure my settings are the "recommended" setup.

Edited by Paab, 09 July 2012 - 03:07 AM.

Paab, on 09 July 2012 - 03:05 AM, said:

Usually a #42 is enough. The needle has nothing to do with the popping.

I suspect a leak somewhere. Probably the copper crush gasket between cylinder head and header pipe. Or maybe a hairline crack in the header.

I recently put a fresh copper gasket in.  No love.  I was thinking of stacking two in there.

OK, this is getting frustrating.  My bike has been running rougher and rougher little by little.  Nothing I do seems to improve it.  I have recently done the valves (mxtime seat work with KW intakes) and they are in spec.  I did the top end and camchain.  The thing is stronger than ever, but still raspy on decel and even misses occasionally on steady throttle.  It was hard to start today too...

I guess I can try a new plug.  any other ideas?  do the ECUs die slowly?

Edited by Paab, 09 July 2012 - 02:34 PM.

At this stage, I would check if any of the cam sprockets are slipping. There is a hole in the sprocket that should line up with the hole in the outer lobe.

And try starting it up at night, if there is a crack in the header you should see flames and glowing edges.

late on this I realize but I vote for the stock piston, or if you want soemthing more expensive, I'd say CP, JE, or Cosworth.  The cosworth is cool because it has the same boxed design as the OEM Kawi piston,  The great thing about the kawi piston is that it uses a shorter, lighter pin than any aftermarket or other brand OEM piston.  It makes more horsepower than an aftermarket piston.  It is a reasonable price, and you can get a 1 or 2 piston (although I have only got a 1 on a new bike and a 2 when I order a spare part).  It is also semiforged, I believe, which benefits from the pluses of both cast and forged pistons.  It is boxed, and it is a great piston.  for the price, I probably will never use anything than a stock piston in my KX250F.  In '12, it even got a tin coating,  There is no issue with the '10 using an '11 or '12 piston.  The '09 would hit the valves with a '10-'12 piston, unless you got a thicker gasket that athena sells and did some good measurements.  Anyway, '10-'12 piston is an awesome piston design...the aftermarkets are catching up to it still.

^{I agree with drzadam. Nothing fits or works as good as OEM. I've seen far more aftermarket top end parts fail than OEM.}