Dominant V4 Piston for the 372

[huskihl]

I may end up doing something like that for the transfers. I think that if the transfers are ground up as high as they need to go then they might be too high if the piston is ever changed out.

But if the piston was replaced, you could machine the cylinder to get the ports back down

 

[Ronie]

But if the piston was replaced, you could machine the cylinder to get the ports back down

How much do you think I would have to take off the transfers to get to 121, 2mm maybe? They are at 128 now.

 

[Ronie]

I was thinking that the 372 has a 38mm stroke so 38 divided by 180 equals .21 so 1 degree eqals .21mm. .21mm x 7 degrees equals 1.47mm 0r 7 degrees. Would that work to figure things like this out. I could be way off, need a smart person to jump in and help me out.

I guess I should be shooting for 119 to get 20 degrees of blow down., not 121.

 

[beaglebriar]

I was thinking that the 372 has a 38mm stroke so 38 divided by 180 equals .21 so 1 degree eqals .21mm. .21mm x 7 degrees equals 1.47mm 0r 7 degrees. Would that work to figure things like this out. I could be way off, need a smart person to jump in and help me out.

Put a ring in the bore and rotate the piston to 121° then mark it and pull the ring out. Keep it simple...if I had to rely on math for everything I'd be screwed!

 

[Ronie]

Put a ring in the bore and rotate the piston to 121° then mark it and pull the ring out. Keep it simple...if I had to rely on math for everything I'd be screwed!

That's the way I would do it. I was just wondering if it could be calculated like that. My last math class was basic math in 9th grade and I made a D.

 

[Funky sawman]

That's why I suggested turning the top of piston down

 

[BonScott46]

I was thinking that the 372 has a 38mm stroke so 38 divided by 180 equals .21 so 1 degree eqals .21mm. .21mm x 7 degrees equals 1.47mm 0r 7 degrees. Would that work to figure things like this out. I could be way off, need a smart person to jump in and help me out.

I guess I should be shooting for 119 to get 20 degrees of blow down., not 121.

372 has a 36mm stroke.

 

[Ronie]

372 has a 36mm stroke.

I didn't know, just guessing.

 

[huskihl]

I didn't know, just guessing.

Gotta be close to .015” per degree. You need about 10* on the mains and 6 on primaries.

So about .150”

 

[Ronie]

Gotta be close to .015” per degree. You need about 10* on the mains and 6 on primaries.

So about .150”

The mains would be the ones closest to the exhaust, right?

 

[huskihl]

The mains would be the ones closest to the exhaust, right?

Correct.

Keep in mind, that’s just how I do it. It may not work for everyone. I like 18 on the mains and 22 on secondaries

 

[Ronie]

Correct.

Keep in mind, that’s just how I do it. It may not work for everyone. I like 18 on the mains and 22 on secondaries

Thanks huskihl, I'll give them numbers a try.

 

[huskihl]

I believe @David Young or @paragonbuilder could figure out the distance for you. My math on it is just a guess, and the error is multiplied by 10 in this case. So I’d want a more accurate number before I started

 

[Ronie]

I believe @David Young or @paragonbuilder could figure out the distance for you. My math on it is just a guess, and the error is multiplied by 10 in this case. So I’d want a more accurate number before I started

I was just curious if it could be figured out that way. I'm going to use a degree wheel on it.

 

[huskihl]

I was just curious if it could be figured out that way. I'm going to use a degree wheel on it.

Hard to get numbers on a degree wheel for marking the piston though (if you’re planning on grinding them into the piston).

You could put on an xtorq jug with the transfer caps removed and raise the piston up 10* above and mark the wiseco through the transfers lol

 

[Ronie]

Hard to get numbers on a degree wheel for marking the piston though (if you’re planning on grinding them into the piston).

You could put on an xtorq jug with the transfer caps removed and raise the piston up 10* above and mark the wiseco through the transfers lol

I'm going to get them on the cylinder.

 

[paragonbuilder]

Let me know if you need some maths done. No problem for me. [emoji41]

 

[Ronie]

Let me know if you need some maths done. No problem for me. [emoji41]

I will, thank you.

 

[David Young]

Yep happy to help. But it seems I’m late to the party and you are already in good hands

 

[Ronie]

After sleeping on it I've decided not to keep this piston. I pulled the top end and it has left two lines by the exhaust. I can't feel anything but they don't wipe off with my finger. I'm sure some will take them off but I wonder why it left them. The coating has started to come off a little and I read in a motocross forum that it's common for that to happen. If anyone want's to try to make it work, send me a PM.