new Wiseco 636M06900

[Roostius_Maximus]

A wiseco arrived for a customer today, its the new symmetrical version without windage at the wrist pin, i know guys have seen it, but i figured i'd post that the weight is 431grams without pin rings or clips

[MICK]

Wiseco had a tutorial in a Snow West (?) mag last winter. They spoke in detail about lessons they've learned making pistons. One aspect I found interesting was the skirt thickness. Apparently the skirts they produced in years past they feel were much too thin and caused the piston to expand at a much higher rate than necessary. So they began thickening the skirts which made them heavier, but they didn't swell as much or as fast preventing a lot of failures that would otherwise have occurred. Did this evolution cross over into the new CR500 piston? I believe it did. Among other things...

[100hp honda]

A wiseco arrived for a customer today, its the new symmetrical version without windage at the wrist pin, i know guys have seen it, but i figured i'd post that the weight is 431grams without pin rings or clips

what size is it, was does the old version weigh ?

[MICK]

Without looking at my book, my 89.25 weighed 290g +/- (old version).

[iggys-amsoil]

And I wonder what the intake thickness was before and now after?

[100hp honda]

the botton part of the skirt is visually thinner on the new version. thats just what i noticed, other than that i havent looked real close to determine what the other differences are.

[MICK]

Some other things Wiseco said they changed:
1) Thicker ring lands
2) Ring lands further apart
3) Thinner wrist pin area

...in case you get a chance to compare.
Again this was in regards to Bike/ATV/Snowmobile pistons abroad. But it seems to coincide with the sudden change in the CR500 piston...so I thought it made sense?

[Roostius_Maximus]

Its standard bore, the pin area, actually every part of the piston looks the same, just less machine work. its on the bench and i have both previous versions there to measure aswell. I'll post more tommorrow

[Roostius_Maximus]

INTAKE FACE THICKNESS
554p2 .127
636 gen1 .132
636 gen2 .103

EXHAUST FACE THICKNESS
.126
.101
.115

INTAKE PORT WINDOW WIDTH
1.938
1.757
1.757
(others oem 1.755 Rockey cycle 1.964 Vertex 1.750 Prox 1.959)

RING LAND TOP of #1 TO BOTTOM of 2ND
.249
.249
.249

BARE PIStON WEIGHT IN GRAMS
360.3
380.2
431.0
(others oem 404.6 RC 379 Vertex 422.7 Prox 418.7)

PIN IN GRAMS
79.4 (69mm)
59.8 (60mm)
62 (60mm)
(others oem 79.4 RC 73.4 vertex 82.2 prox 77.4 [all 69mm pins])

OTHER INFO
636 gen1 piston is machined to accept clips for both 60+68mm wristpins

[dannygraves]

I have run all 3, and honestly never noticed a difference. the old old one is the one I'm running in the gen-3 on a std bore.