Piston/Rings Question

[waterfowler]

OK I have an 86 250R all stock (original). The piston is original with (now) siezed rings. After reviewing information provided on this site (THANKS) I have decided to have the cylinder bored. Now for the question. Traditionally I have replaced my pistons with Pro-X pistons in my X's. I understand that Pro-X is a cast piston and that the Wiseco piston's are forged. I likewise understand that the forged pistons are better. Any advice on which to go with, and also what exactly is the difference between the two, advantages/disadvantages?
Thanks in advance,

I am no master....and far from it.....but i have always used Wiseco pistons...i guess its just a pet peve (sp?) of mine!!! but anyway....i believe forged pistons are lighter and harder which helps in the long run with heat...but i can be wrong...like i said im no master!!!

[catfishwhisker]

With the Wiseco (forged), you can run a tighter clearance between the piston and cylinder. The forged piston will not "swell" like the cast piston will. I'd always go with the forged piston if your budget will allow. If your not going to be doing any racing, the cast piston should be fine though.

[kimmer250r]

Hey waterfowler,
Take it down to Mel's in mattawan. He does very good work and great pricing. He is going to put a rod kit and new crankbearings/seals in my bottom end of my 86 R for $400. Thats parts and labor. He only charged my friend $400 to rebuild his 200x motor. He uses wiseco pistons. Hope this helps.

I have talked to my boss about this and he showed me with a press. Put a forged piston in a press and try to crush it. do the same thing with a cast and it will shatter alot sooner. Just to show how much stronger they were. You can't go wrong with wiseco. Why don't you give me a call at the shop and I can get you a good deal on your piston and gaskets. we ship daily and it will only cost you $6 248-674-0663 ask for Drew.

[waterfowler]

Once again, thanks for the info guys! Looks like it will be Wiseco. The difference in price is only $20. And like my dad always says, Go big or go home. I think he rubbed off on me. Kimmer, thanks for the heads-up on Mels, it's right around the corner from me. I have only purchased tires from him so far. I will be calling him and Drew tomorrow for parts and service. I appreciate all the help guys!
86 R will live again!

[ATC'R]

I would stick with a stock or an aftermarket "Cast Aluminum" piston for normal use as they are more forgiving. Forged pistons require care and extra time when first starting a cold engine as they are more prone to cold seizure. You are also more likely to seize up a forged piston due to improper jetting as compared to cast. Forged pistons have much less silicon content than cast pistons, so they expand a lot more and faster when heated compared to cast pistons. Because of this they require additional cylinder wall clearance. Cast pistons actually have a tighter piston to cylinder wall clearance, not forged! Because of this, cast pistons have better oil control (four stroke), less noise and rattling on start up, especially on cold mornings, Also because the piston is not rocking back and forth in the cylinder it translates into less wear and longer engine life. Wiseco "Forged Aluminum" pistons are good for high end use(nitrous, high compression,etc) if set up properly and serviced regularly, but have their draw backs. Your bikes original stock "Cast" piston lasted 17 years I think the reliability has proven itself already.

[catfishwhisker]

ATC'R: Your 100% right! I went back and looked at what I wrote and said "You idiot!". I don't know what I was thinking when I posted that. Yes, you do run a tighter clearance with the cast piston. The forged piston will "swell". I guess my brain was farting that night! Sorry about that WATERFOWLER.

[TimSr]

I would agree with ATCr in everything stated, other than the advice not to use the Wiseco piston. If you are getting a bore job, Wiseco is more standard than OEM, and have proven to be very reliable. The biggest problem is most guys shop around and end up taking it to "Earl" down on the corner, to bore it, because he's the cheapest guy in town. Of course, "Earl" never even asks what kind of piston youll be using, and drills out .020" like you told him to, instead of realizing that bore tolerance's are different depending on your piston.
Very few motorcycle shops do boring any more. Every local shop here sends them to Wiseco for boring, and it comes back with a new Wiseco piston and rings, and a Wiseco warranty, at a cost of $150-$200, most of which is for the new parts. Ive had about 20 bore jobs done, and one had a problem and was redone, with new piston and rings at Wiseco's expense. It is my opinion that if you have your shop send it out to Wiseco to be properly bored for a Wiseco, its unlikley youll have a problem.

[waterfowler]

Once again, thanks guys. After re-thinking the situation, I have decided to go with the Pro-X instead of Wiseco. One comment really hit me and that was that the original cast piston/rings lasted this long why wouldn't a new set hold up well. I run Pro-X in all my 4 strokes and they seem to work out well. Thanks for the info!

[YTZ250N]

We do machining at my shop I just did the top end on a Poo-laris XLT 650. Its not too bad to do using good gauges and equipment. With that I could get it right down to a half thousandth of where i needed it.