365 piston swap

[duramax99]

Just wondering if anyone knows of a piston that will work in a 365 that is a bit taller? I can set the squish band but I'm not setup to machine the base of the cylinder.

 

[w8ye]

I don't see anything that will work

The 61 pistons have a .020" lower crown and the skirts are wrong

The 262 piston has a .060" lower crown

The 036 piston has a .020" lower crown and the wrist pin is wrong

 

[duramax99]

So no easy fix like the 372s. Well thats not what i wanted to hear haha.

 

[Mastermind]

Going away from the full skirt piston don't work well for me anyway......

 

[duramax99]

Ive built a few 372s with windowed pistons and they seem to run as well as the ones ive done without. But then again ive never tried the exact same cylinder with a full circle then a windowed piston.

 

[Mastermind]

Ive built a few 372s with windowed pistons and they seem to run as well as the ones ive done without. But then again ive never tried the exact same cylinder with a full circle then a windowed piston.

I just did a BB with a 272 piston......I was disappointed with it.

 

[w8ye]

A big bore with a 064 piston is not too bad.

 

[wigglesworth]

I find no reason to use anything but a 365 piston....

 

[duramax99]

Just trying to avoid cutting the base of the cyl. I dont have a lathe yet. I had a few mandrels made up so i can cut the squishband though.

 

[davebull]

I just did a BB with a 272 piston......I was disappointed with it.

Are you still tinkering with this project or is it in the scrap bin?
Did you get it running again after you seized the first piston?
I really want it to turn out well, I just got my order on 5 272 pistons but I could probably make them paper weights if there more useful on the bench than in a 372

 

[davebull]

A big bore with a 064 piston is not too bad.

That's what I'd do....

 

[MCW]

Sometimes there are really good reasons to fit different pistons. Sometimes there isn't

 

[Mastermind]

Are you still tinkering with this project or is it in the scrap bin?
Did you get it running again after you seized the first piston?
I really want it to turn out well, I just got my order on 5 272 pistons but I could probably make them paper weights if there more useful on the bench than in a 372

It ran good enough that many would be very impressed.

I wasn't.

 

[MCW]

It ran good enough that many would be very impressed.

I wasn't.

You're a hard man to please Randy. Sort of a good trait when building and selling saws.

 

[Mastermind]

You're a hard man to please Randy. Sort of a good trait when building and selling saws.

It was strong......but slow. It had plenty of power, but was missing RPM. Most of the 372s we build will still 4-stroke at insane rpm, but this one seemed to go lean early. I'll play with some more when I get time......I want to use the kit's piston to compare.

 

[davebull]

It was strong......but slow. It had plenty of power, but was missing RPM. Most of the 372s we build will still 4-stroke at insane rpm, but this one seemed to go lean early. I'll play with some more when I get time......I want to use the kit's piston to compare.

We're you running the xt carb randy?

 

[Mastermind]

We're you running the xt carb randy?

Yep

 

[davebull]

Yep

Do you think you would get more rpm out of a 385 carb or would it not make a difference?
Just remember I'm still learning....:msp_biggrin:

 

[Mastermind]

Do you think you would get more rpm out of a 385 carb or would it not make a difference?
Just remember I'm still learning....:msp_biggrin:

It didn't seem to have enough case compression.

 

[Trx250r180]

It didn't seem to have enough case compression.

i hear that may happen when you leave out a crank bearing :msp_wink: