Dominant saw V4 371 build

[mettee]

If your at .016, you could sand out .004 using an old piston with paper on it. Especially if you feel like you are hitting.

If the bearings wear in and some more tolerance happens you might start to really hit badly and wreck the saw.

 

[Funky sawman]

Piston has some sort of ceramic thermal coating on top, dont really want to mess with that

 

[Funky sawman]

And it's a pop up, not sure what u mean mettee

 

[Dub11]

I think I'm gonna sell that piston and just build the saw with factory piston. I'm completely out of basic resources. My solder is too thick to begin with and would have to buy solder. Excuses excuses I know but that's my life right now sorry

I'd call up the peeps you got the piston from. If its supposed to be a "plug and play" it shouldn't be given you these problems. Maybe the piston pop up is to big?

 

[mettee]

Use a flat top stock piston, slap some sticky back paper on it and trim the rest off with a razor. You can drop that down in the cylinder and spin it and remove the .004 pretty easy. Or if you have a wood mandrel that will work too.

Yeah no need to mess with the dominant piston at all.

 

[Funky sawman]

Well, like I said if crap is gonna happen, I'm always found in the middle of a crap storm. So I pulled the ring, reinstalled the thin gasket, and tightened the jug down, no more hitting, turns over smooth. Wtf, this is beyond my current mental capacity

 

[Ronie]

I personally wouldn't run it until I found out how much clearance I had. If your only a couple of thousandths from kissing the cylinder in a spot, you could have a big problem once you start using it.

 

[Funky sawman]

The ring looks like its hanging up at the top of the plating. The ring height is further up the piston that the factory single ring

 

[Ronie]

The ring looks like its hanging up at the top of the plating. The ring height is further up the piston that the factory single ring

That's odd, never had that happen.

 

[Funky sawman]

Well with piston out and ring on piston, it doesn't catch when shoved all the way into bore. But I dont know why having the ring on makes a difference. Weird part is the gasket. One corner is .011, opposite corner is .016. Studying the piston it looks like the chain side of the piston has shiny mark on it but that's it

 

[Funky sawman]

I think the old gasket was compressed at .020

 

[Funky sawman]

Just went through packaging, the gasket was packaged with cardboard backing....NOT A OEM GASKET. it's a hiway gasket

 

[mettee]

Well with piston out and ring on piston, it doesn't catch when shoved all the way into bore. But I dont know why having the ring on makes a difference. Weird part is the gasket. One corner is .011, opposite corner is .016. Studying the piston it looks like the chain side of the piston has shiny mark on it but that's it

Get rid of that gasket.

Put the ring on the dominant piston and put it in the bore, push it all the way up and make sure it doesn't hang on the top edge. I forget what they call that.

 

[Canadian farm boy]

Get rid of that gasket.

Put the ring on the dominant piston and put it in the bore, push it all the way up and make sure it doesn't hang on the top edge. I forget what they call that.

That’s the ring of death. Where the plating stops before it gets to the squish band.

 

[Funky sawman]

It doesn't catch

 

[huskihl]

Well, like I said if crap is gonna happen, I'm always found in the middle of a crap storm. So I pulled the ring, reinstalled the thin gasket, and tightened the jug down, no more hitting, turns over smooth. Wtf, this is beyond my current mental capacity

You may be hearing the ring when the piston changes direction

 

[Marshy]

Get rid of that gasket.

Put the ring on the dominant piston and put it in the bore, push it all the way up and make sure it doesn't hang on the top edge. I forget what they call that.

Ring of death. Usually after the squish band it turned and there us a small section of the bore that has no plating. Some times it's a smaller diameter than the bore also because it's hard to get the combustion chamber cut all the way against the cylinder wall.

 

[Funky sawman]

Nope, I can actually feel the flywheel stop at tdc, without the coil installed. It doesn't take much effort to continue rotating past tdc though.

 

[Funky sawman]

Found my issue with the ring......no issue. When I tightened cylinder down with that after market gasket I used two screws on opposite corners, the piston didnt hit. Then I found if I tightened all 4 corners then i have contact. Best case scenario is a factory gasket that's .020 and I end up with .010 squish which is scary tight

 

[Funky sawman]

I stuck a .010 feeler gauge on each side of the jug to space cylinder away from crankcase and tightened the jug down, at this thickness the piston just barely kissed the squish band. So I must need a .030 gasket?