Which top end?

[k-dog]

I just installed the S.P.I. fix kit but i used arctic cat hypershift pistons instead of the s.p.i. anyone else use the S.P.I. kit

 

[Norway]

I just installed the S.P.I. fix kit but i used arctic cat hypershift pistons instead of the s.p.i. anyone else use the S.P.I. kit

So.. Cat pistons in the pro?? From the 800 then. What year?

Thanks.

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[tuneman]

So.. Cat pistons in the pro?? From the 800 then. What year?

Thanks.

Sent fra min GT-I9295 via Tapatalk

The whole "shim" style fix kits came about because someone discovered that Cat pistons would fit in a Pro as long as they shimmed for the 1/4" longer length. It's the only truthful reason for the shim. There's no other advantage with it.

 

[Norway]

The whole "shim" style fix kits came about because someone discovered that Cat pistons would fit in a Pro as long as they shimmed for the 1/4" longer length. It's the only truthful reason for the shim. There's no other advantage with it.

So you don't buy the increased efficiency from a slightly larger case volume?

RS

 

[tuneman]

So you don't buy the increased efficiency from a slightly larger case volume?

RS

Sure, it'll make it more efficient by about 1% or so. Had a friend rebuild 2 sleds last season, side by side. One with RKT pistons only and one with a MTNTK shim kit. No difference in performance between them.

 

[diamonddave]

The whole "shim" style fix kits came about because someone discovered that Cat pistons would fit in a Pro as long as they shimmed for the 1/4" longer length. It's the only truthful reason for the shim. There's no other advantage with it.

You couldn't be more wrong with this statement.

Sure, it'll make it more efficient by about 1% or so. Had a friend rebuild 2 sleds last season, side by side. One with RKT pistons only and one with a MTNTK shim kit. No difference in performance between them.

You couldn't be more wrong with this statement as well. Without asking a ton of questions, you are comparing apples and oranges.


The MTNTK kit has been the exact same kit since 2010.

MTNTK fixed a motor that RKT said couldn't be fixed.


RKT's has changed from no shim (screaming all over the internet about how bad it is to use a shim) to using a shim (surprise) back to no shim and now whatever he has in stock and pistons from Wossener to Wiseco. Search his posts and you'll find him absolutely blasting Wiseco.

Why does he use them now?

 

[Merlin]

I'm not an expert or metallurgist but somewhere along the line Wiseco changed the composition of their pistons to provide a tougher finished product, something less prone to skirt collapse.

I think this is why we are seeing the success with them being used in these "Fix kits".

I can tell you that if they were the same make up as the pistons that we installed on several big bore builds years ago, the skirts start to collapse immediately & then you end up with anywhere from .003" to .005" additional PTCW clearance. Lots of engines can tolerate this excessive clearance just fine but the '11 / '12 CFI-2 isn't one of them. LOL

 

[tinkerjohnson]

Rkt

Diamond Dave

RKT's has changed from no shim (screaming all over the internet about how bad it is to use a shim) to using a shim (surprise) back to no shim and now whatever he has in stock and pistons from Wossener to Wiseco. Search his posts and you'll find him absolutely blasting Wiseco.

Why does he use them now?

Just to clarify a couple things to that you must not be aware of with rkt kits. He has three different kits. One is direct replacement Pistons. Two is a drop in kit (rev one) no shim. Three drop in kit with a shim (rev two) it's not a m-8 piston in a Polaris engine, the shim is thicker and the piston is a completely different design than anything out there (if you haven't seen one you won't understand I'll post a pic). As far as the change in piston manufacture to Wiseco, the reason is simple, wosner wouldn't make his specs anymore they wanted him to use their design (which if you have looked at the new wosner piston wow junk! skirts are very thin and cheap) and Wiseco agreed to make pistons with his specs and his design, and I believe Wiseco has improved on their quality aswell. So before you throw out misleading info have the facts in place first. This statement you posted is very misleading to others looking for good information about (fix kits)

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[tinkerjohnson]

Rkt rev 2 piston vs Polaris stock piston

View attachment 274347

 

[tinkerjohnson]

Side view

 

[peaceofwork]

weisco

so if i see weisco pistons on ebay how do i tell if they are the newer style or {the good ones} ?
2015 polaris are the best variation of the stock piston?

 

[peaceofwork]

at what point did the Weisco Pistons get better? What's the new part number ? And what's the old number? If anyone knows post the part numbers them up here.

 

[peaceofwork]

For Weisco I find
2010/2012 pro Number sk1396
2010/2015 pro lite 2459mo8500 add says new forging design .
Would the last one be the best to date from stock Weisco Pistons ?

 

[trestlecreek]

Ditto on this last question. Great thread, I'm in the same boat...which route to go???

 

[Nyheim]

Just rebuilt my 13 Pro RMK with Wössner pistons. Not the RK-TEK design, but Wössners own design. A lot of people here in Norway runs these pistons, and they hold up damn good. Reccommended!

 

[trestlecreek]

Anyone run the SPI fix kit?

 

[peaceofwork]

my ebay 168.00 pair of weisco pistons with 5 thou clearance are working just fine and i have 600 miles on them now, compression has not changed ,