NWP MS260 Build

[wcorey]

I thought @wcorey was working on something to cut the top out a little? His invention was pretty slick.

Point of this is that Al is sanding the band to closely match the radius of the piston dome rather than simply cutting it angled but at a straight line to more or less match.

Most any mandrel type of cutter could do the straight angle by tipping the cutting bit but a purpose ground bit would need to be made to get the radius. Easier to do it with Al's method unless you were doing a ton of them. Particularly when you would sand it anyway after mandrel cutting so to even up chatter marks that sometimes happen with that method.

 

[RI Chevy]

OK. I got you. But I knew you were developing that cool cutter. [emoji106]

 

[paragonbuilder]

I think I can get a little more with a flat top because the exhaust can be dropped more. But even with a high exhaust, these saws can really run.

I do like the unaltered piston for simplicities sake though....

Couldn't agree more on the piston.

The flat cut I do buys me 3* more of exhaust roof, but its a ton more work.

The band match to the piston should bump the compression up more than a tapered band cut and keep the squish more symmetric. When I've cut on an angle, you get a tighter squish towards the chamber at a certain point.

More than one way to skin a cat for sure.

Is this because if you cut to get the exhaust that low with the domed piston the compression goes to high? Cutting the piston flat helps bring it down?

 

[Mastermind]

Is this because if you cut to get the exhaust that low with the domed piston the compression goes to high? Cutting the piston flat helps bring it down?

Cutting it flat lowers the exhaust, but makes the base too thin for comfort sometimes.

 

[paragonbuilder]

I've been pondering this for a half hour...
if the piston is cut flat from the outside corner, and re installed in the saw, timing should stay the same, no?
Isn't increasing the distance from the top of the exhaust port to top of piston at TDC the only way to lower the exhaust?
I'm having trouble picturing how cutting it flat lowers it on its own.

The only thing I can think is if you consider the top angle of the piston aiming at the port, but I can't see 3 degrees.

What am I missing? [emoji848]

 

[RI Chevy]

You have to experiment for yourself Dan. It's the best way to learn and debunk any myths. To see it for yourself in your own eyes.
Nothing ventured, nothing gained. Lol

 

[dall]

what al and randy are saying is if you flatten the squish area on the 026 /260 you are adjusting the timing al did mine with a flat top piston and i also have a spare

 

[RI Chevy]

You got spares for the spares! Hoarder. Lol

 

[drf256]

I've been pondering this for a half hour...
if the piston is cut flat from the outside corner, and re installed in the saw, timing should stay the same, no?
Isn't increasing the distance from the top of the exhaust port to top of piston at TDC the only way to lower the exhaust?
I'm having trouble picturing how cutting it flat lowers it on its own.

The only thing I can think is if you consider the top angle of the piston aiming at the port, but I can't see 3 degrees.

What am I missing? [emoji848]

It's easier to cut it flat and take that much out. As long as the edge is the same depth, the exhaust roof should stay the same.

The big issue here is that its an arc and not an angle. Conceivably, one could add a small cutter at an angle on the piston top to open the chamber a bit.

Opening it at the same arc as the dome should result in an even bigger squishband and a smaller chamber like you say Dan.

 

[Mastermind]

I've been pondering this for a half hour...
if the piston is cut flat from the outside corner, and re installed in the saw, timing should stay the same, no?
Isn't increasing the distance from the top of the exhaust port to top of piston at TDC the only way to lower the exhaust?
I'm having trouble picturing how cutting it flat lowers it on its own.

The only thing I can think is if you consider the top angle of the piston aiming at the port, but I can't see 3 degrees.

What am I missing? [emoji848]

You are only thinking about the piston. We also cut the squish band flat. Then the base has to be cut to set the squish clearance.

See?

 

[stihl_head1982]

Readin and learnin.

 

[paragonbuilder]

You have to experiment for yourself Dan. It's the best way to learn and debunk any myths. To see it for yourself in your own eyes.
Nothing ventured, nothing gained. Lol

Ok Jeff... you are no longer allowed to ask about sq filed chain. You need to buy some and figure it out for yourself...[emoji12]

 

[paragonbuilder]

You are only thinking about the piston. We also cut the squish band flat. Then the base has to be cut to set the squish clearance.

See?

I do!
I thought that you were suggesting that just cutting the piston flat helped lower the exhaust on its own. I'm. It not sure how I arrived at that now that I read back through... lol.
Carry on!

 

[RI Chevy]

Ok Jeff... you are no longer allowed to ask about sq filed chain. You need to buy some and figure it out for yourself...[emoji12]

That's why I still Round file!!
Lol

 

[paragonbuilder]

That's why I still Round file!!
Lol

I'm sensing an unwillingness to learn...
you shall from here on out be called "Pot"!

 

[RI Chevy]

WTF is pot? Lol

 

[dall]

pot and kettle

 

[dall]

lol come on jeff even i know the old term

 

[RI Chevy]

Lol. Sorry. I don't get out much.

 

[SOS Ridgerider]

Lol. Sorry. I don't get out much.

Come on Pot! Even I know that term, and I'm not from around here! Lol