372xp with a 268 50mm pop up piston.

[Nitris223]

Which piston would you guys use for a 372 xp. I'm doing a little experimenting with a AM cylinder before I use the new OEM cylinder I have.
These pistons came with the saw that was a xtorq now being converted to a 372xp OE.
The windowed piston on the left looks nicely made and the rings have a small HW on them, it was just in a small ziploc bag. Maybe hyway rings.
The slab side piston was in a Farmertec box. Slightly lighter piston also .
I know which ever one I use will need to be machined into a pop up depending on the squish clearance which I have a lathe for that.
I do have a couple Caber rings also.

Still waiting for my right angle hand piece to get here before I can do any port work.

I searched the forums quite a bit and I can't seem to get a solid answer if guys are still cutting down the cylinder wall flush with the base or not. It seems to be 50/50.

Also are the upper transfer ports and 2 different heights. Looks like the port closest to the intake is higher then the rear port. Maybe a degree or 2. Haven't checked with the timing wheel yet. I don't have my OEM cylinder yet to verify if they are the same. . Waiting for a buddy to pick it up for me in a couple weeks.

The AM cylinder I have I checked the timing a while ago and it is
IN 75
EX 102
TR 125
SQ .20 NBG.

My plan is to set the squish with a base gasket to the stock 2 rink piston then machine the 268 piston to work.

This way if I don't like it I can always go back to the stock piston and still have good compression

 

[beaglebriar]

@Czed has done this.

 

[Nitris223]

I have the same post on another site but I always find that site to be a little hostile at times and not open to other ideas.

 

[Stump Shot]

Slab sided piston works fine, there's no need for windows on a bottom feed cylinder.

 

[Czed]

Stumpshot cut those pistons for me
The compression landed in the 180s on stock cylinders
Easiest starting 70cc saws I've ever seen
It must be the lightweight mass of the pistons
But not the strongest of my 372s
The regular piston saws are stronger.

 

[Stump Shot]

Stumpshot cut those pistons for me
The compression landed in the 180s on stock cylinders
Easiest starting 70cc saws I've ever seen
It must be the lightweight mass of the pistons
But not the strongest of my 372s
The regular piston saws are stronger.

Pop-ups mess with the transfer flow over the top of the piston, taking away from the benefits gained.

 

[srcarr52]

Pop-ups mess with the transfer flow over the top of the piston, taking away from the benefits gained.

They don't seem to really bother anything at 0.020" with a 45° angle to the pop up.

 

[Stump Shot]

They don't seem to really bother anything at 0.020" with a 45° angle to the pop up.

For use in a stock cylinder it takes more than that to get it to work out correctly, I can't remember the number exactly just now, and not sure if it's still in with my notes, but I'll look.

 

[huskihl]

For use in a stock cylinder it takes more than that to get it to work out correctly, I can't remember the number exactly just now, and not sure if it's still in with my notes, but I'll look.

It’s 035 or 040 to make it work on a stock cylinder.

I said the same thing on AS. Apparently an honest opinion makes that site “hostile”lol

 

[wcorey]

It’s 035 or 040 to make it work on a stock cylinder.

I said the same thing on AS. Apparently an honest opinion makes that site “hostile”lol

Oh no, popup wars...!

 

[Czed]

It’s 035 or 040 to make it work on a stock cylinder.

I said the same thing on AS. Apparently an honest opinion makes that site “hostile”lol

It must be your accent.

 

[srcarr52]

It’s 035 or 040 to make it work on a stock cylinder.

I said the same thing on AS. Apparently an honest opinion makes that site “hostile”lol

But there are 5 pages on a POS EPA compliant gas can being "perfect".

 

[bretts]

It’s 035 or 040 to make it work on a stock cylinder.

I said the same thing on AS. Apparently an honest opinion makes that site “hostile”lol

A mod banned and removed me from that site because he was convinced he was right and I was wrong, he let the mod power go to his head.

 

[Ketchup]

There are multiple threads on AS about the 268 piston in a 372. Unfortunately that place has gone to the dogs.

I’ve done both slab and windowed. The slab feels stronger but neither holds a candle to a machined and ported 372 with the full circle slug.

 

[Czed]

There are multiple threads on AS about the 268 piston in a 372. Unfortunately that place has gone to the dogs.

I’ve done both slab and windowed. The slab feels stronger but neither holds a candle to a machined and ported 372 with the full circle slug.

Simonizer was well known for building that style of 372
I don't know what all he did but he built a bunch of them for logger's they were really happy with them.

 

[Ketchup]

I ran one of Simon’s saws. It was okay.

 

[Maintenance Chief]

Who makes the full skirt piston?

 

[huskihl]

Who makes the full skirt piston?

The standard 372 piston. KS, Mahle, etc