Choosing right pistons for rebuild

[Polish jet pilot]

Hi all,

I was wondering what pistons would you recommend for my top end rebuild (9 seasons old). I wish to go higer in cc's but stay with the original 61x cylinder (no BB in this boat). I had a poor experiance with Pro-x, although they make OEM style pistons, which are widely recommended. I was thinking WSM platinum series, but I don't think they go up to e.g. 83mm??

Wisecos: a bit afrad of them - some say only wisecos, other say - stay away from them (but maybe that is due to the misuse of them in certain applications, or bad exploitation?)

What is SUDCO? Seen them on ebay..?

The setup will be ported 61x with bpipe and some bolt ons...

Thanks!

 

[luker]

ive used vertex myself for years with no problems, heard pro x are good as well!

 

[D-Roc]

wiesco. what is there to be scared of. that is all i ever use, and never blown a motor with them yet.

 

[Polish jet pilot]

The fears with Wisecos around here are with their fittment. As theya are forged, they tend to expand with temperature. If they are wrongly fitted to sleeve they will slap around the sleeve - and then seize.. BUT that is what folks around here say (racing guys)

Secondly I think that wisecos are flat on top. OEM pistons are domed. This does matter but not sure what is better (issues with squish, deto, etc.)

 

[QJS]

The Wiseco's made for Yamaha are not flat top, they are a direct replacement. You have to bore with the correct clearance and warm the engine from cold but you should be doing that anyway. Never had a problem with them, but then I've never had a problem with Prox either its just something about the quality of Wiseco that makes me prefer them.
Chris.

 

[chad]

until just recently , All I ran was Wiesco pistons. I just rebuilt my top end and decided to save about 100 bucks and try the WSM piston kit. I can feel that the wiesco pistons were lighter and would rev faster , more snappy.. it feels like I slowed down my motor by going to WSM .

 

[Polish jet pilot]

Chris, Chad, that is good advice. I guess it will be the wisecos...faster revving sounds nice...

 

[58vwragtop]

Go with the Wiseco. There is a reason why they build "high performance" pistons and not "oem" replacement. Find a good machine shop to bore the cylinders. The clearence specs are listed on the box of the piston. Try to find a shop that is familiar with 2 strokes so they know how to chamffer the port right. Good shops would be PWC, outboard boat, or I found that go karting shops are great.

 

[Polish jet pilot]

What about SUDCO? What brand is that? I've heard that people use them... are they a cheap or good piston?

 

[58vwragtop]

From what I understand the Sudco is the same as the ProX. They are just an older piston, then they changed marketing to a different name. If you are going to run pretty high compression I would get a forged piston (wiseco). The ProX, stock Yamaha, Sudco, and other cast are good pistons. I would rather run the forged on higher compression engines though.

 

[SUPERJET-113]

Wisecos are superior and my favorite, but cost more. They are forged, stronger and lighter and if part of the skirt breaks its doesn't crumble like a cookie into a hundred pieces like a cast piston does.

For cast pistons I prefer in this order: Vertex, OEM(ART), Pro-x, WSM Paltinum series.

 

[Rickster]

Bigbore = Wiseco flat top
stock bore SJ = Pro-x
couch = WSM Platinum

:headbang:

 

[Polish jet pilot]

Can I go safely to 84mm? I know group K even says 84.5mm is still "ok"...then I could use Yam 760 std pistons.....as pin size etc are the same...what about squish clearance?

 

[Matt_E]

You're not gaining much by going to 84mm and you will loose opportunity for overbore.

 

[bigpine007]

pistons

Vertex pistons that are sold in the US are made by WSM. Somebody at WSM told me this. The box still says made in Italy.

 

[Kennay]

It's probably the other way around... perhaps for their (WSM) top of the line piston. This is just speculation due to WSM's junk factor.

 

[bigpine007]

pistons

I got these two very different pistons out of an unopened Vertex top end kit. I had to call the manufacturer which ended up being WSM.

 

[Polish jet pilot]

Anybody has pistons for sale?

 

[B_RAD_BALLA]

i love my wisecos. i pulled my motor apart after a LONG season of abuse and im going to put it back together as is and run it another year. all looks well...

 

[Polish jet pilot]

Subject solved for now - 2 x new complete sudco + 1.5mm @ 110 USD... I think at that price...good choice.. we will see... I heard SUDCO is oem Yamaha, and now they changed the name to PRO-X (few years ago).

Thank you all for help!