Dominant piston v4 tight squish

[blsnelling]

Requiring thicker than OEM gaskets or stacking them is not a desirable scenario for what's supposed to be a drop in piston. They simply made the piston too tall. I don't like the bevel on the exhaust side either. That's a bandaid that actually hurts compression and squish velocity. Not a great idea.

 

[Matthew Steingass]

Requiring thicker than OEM gaskets or stacking them is not a desirable scenario for what's supposed to be a drop in piston. They simply made the piston too tall. I don't like the bevel on the exhaust side either. That's a bandaid that actually hurts compression and squish velocity. Not a great idea.

Isn't the intake skirt too short as well? Netting too low of an effective intake port lowering. Raising the entire cylinder .013 effectively raises the intake port to a more moderate level. Benifical for exhaust port as well. Transfers benefit from the raised crown. Popup negates the exhaust bevel volume loss. I feel that the whole piston is a bandaid for porting but the benefits outweigh the drawbacks. They need to include another bandaid aka new gasket. tn-9014 can probably be had in various thicknesses as well

 

[blsnelling]

IMHO, the piston is defective and a bad design all around. I would "fix" it by turning the crown down until I had sufficient squish. That would get rid of the unwanted bevel on the crown as well.

 

[Matthew Steingass]

IMHO, the piston is defective and a bad design all around. I would "fix" it by turning the crown down until I had sufficient squish. That would get rid of the unwanted bevel on the crown as well.

Can't wait for V5 lol. Is Andy from dominant on here?

 

[Yotaismygame]

I still vote the 268 piston. I think this winter ill do the comparison between the 268 piston and dominant piston. Both new in a new oem untouched cylinder. Same bar and chain in the same log. Ill do port timing, compression comparisons as well. Which will be better? Maybe ill do a ported comparison too..

 

[Yotaismygame]

Can't wait for V5 lol. Is Andy from dominant on here?

I'm not sure

 

[blsnelling]

I'm a fan of their earlier piston, just not this one.

 

[Andyshine77]

Too many compromises on this piston IMHO. With manufacturing variances it's almost impossible to get a plug and play part when you start trying to get things this close. Flat top pistons are the best performers and cutting the exhaust side of the piston down for anything other than researching exhaust port timing, is a hack job. Sorry but I wouldn't use that piston, and I'd want my money back. For what they're charging I'd want something a whole lot better.[emoji111]

 

[Matthew Steingass]

Oh well. I'm gonna run it. I already got their hat and stickers so theres no turning back lol. After this goes together I'll probably move on to a ms200t so I can clear trails by bike. Thanks guys.

 

[Andyshine77]

Let us know how it turns out, never know could run real well.[emoji111]

 

[Matthew Steingass]

Squish is at .017 now. Pin to crown height was .683 on the v4 and stock is .649. Plugged the decompression valve. Might be able to run her before work today if we have a late start.

 

[blsnelling]

Squish is at .017 now. Pin to crown height was .683 on the v4 and stock is .649. Plugged the decompression valve. Might be able to run her before work today if we have a late start.

That's plenty.

 

[Yotaismygame]

Squish is at .017 now. Pin to crown height was .683 on the v4 and stock is .649. Plugged the decompression valve. Might be able to run her before work today if we have a late start.

Now? Did you end up adding a thicker gasket?

 

[Matthew Steingass]

I did. But the gasket came in at .0275 and compresses easily. Had to add 2 sheets of drawing paper. My dad has a lathe and I'll be bringing this piston with me the next time I visit.

 

[Yotaismygame]

Unless he’s machined chainsaw cylinders before he’s going to have a difficult time the first go around. Not a difficult thing to do but if you have zero background doing it or have not even heard of machining chainsaw cylinders it will be a learning experience for sure.

 

[blsnelling]

Just turn the crown down, increasing the pop-up by about .020".

 

[Matthew Steingass]

Just turn the crown down, increasing the pop-up by about .020".

Exactly. And like you said it gets rid of the .020" exhaust bevel

 

[Andyshine77]

Exactly. And like you said it gets rid of the .020" exhaust bevel

Should be making a good bit of compression after the machine work.[emoji106]

 

[Yotaismygame]

I did. But the gasket came in at .0275 and compresses easily. Had to add 2 sheets of drawing paper. My dad has a lathe and I'll be bringing this piston with me the next time I visit.

My mistake. I swear your post said cylinder. Turning the piston is no big deal at all.

 

[Matthew Steingass]

Should be making a good bit of compression after the machine work.[emoji106]

Between the bevel delete and larger popup I bet. Wonder how close the spark plug will be.