Aftermarket MS660 Performance

[Stihlmar]

OK, I'll be on the lookout for a used OEM

If you find some. Let us know. Lol

 

[brshephard]

Here's a video with a fresh grind and the rakers at .030. Seems faster, pulls a big chip.
What should I try next?

With an 8 pin.

 

[drf256]

Your ex roof looks a bit flat to me.

Next? Lose the popup and get the comp down to 180-190.

After testing that, next try to open the ex more by adding a deflector to the Fly side.

 

[brshephard]

Your ex roof looks a bit flat to me.

Next? Lose the popup and get the comp down to 180-190.

After testing that, next try to open the ex more by adding a deflector to the Fly side.

I was hoping you'd chime in.
So how flat is too flat?
Here's the cylinder in question


My stock 064 for comparison


And an ms440 jug on the bench

 

[Wonkydonkey]

I can see why the 440 is on the bench it’s been eatin straight gas

 

[drf256]

Depends on width to a degree. Looks too flat to me, but if it’s running great and hasn’t caught a ring then it’s probably OK.

You can cheat a bit and chamfer the inside of the plating assymetrically. Wider towards center and narrower on edges. The piston will see more of an arc.

 

[brshephard]

I can see why the 440 is on the bench it’s been eatin straight gas

Yep! Put it right in my price range.

 

[brshephard]

Depends on width to a degree. Looks too flat to me, but if it’s running great and hasn’t caught a ring then it’s probably OK.

You can cheat a bit and chamfer the inside of the plating assymetrically. Wider towards center and narrower on edges. The piston will see more of an arc.

Good enough for who its for I guess.
I did go with a pretty conservative bevel though, maybe that's why its held up.

How about compression. Have you found cons to running 200+? Or is 180-190 the sweet spot?

 

[Wonkydonkey]

The compression is a diminishing return at a certain point. Takes more power to compress,

So I’m guessing drf256 is quoting the sweet spot
And if you read around the net you should see the experts quoting a ceiling figure, but it is less than 200.

Cheers

 

[brshephard]

The compression is a diminishing return at a certain point. Takes more power to compress,

So I’m guessing drf256 is quoting the sweet spot
And if you read around the net you should see the experts quoting a ceiling figure, but it is less than 200.

Cheers

Yeah, seems like most guys willing to share there numbers are right under 200. But then you got JMS running like 240 and hauling ass.
I'll try 190ish and see how it goes, new cylinder should be here friday.

Anybody try the exhaust lower than 100? 101 maybe?

 

[MustangMike]

Don't pay attention to anything JMS says, He can build a strong saw, but he also lies, so don't trust anything that comes from him.

 

[Stihlmar]

I’ve got one at 102/120/82 AM jug squish and base cut. Intake filled. Stock port widths. Runs decent with bridge ports. Working ports in stages to see individual gains.

I Do not know right from wrong in any way. Just got to much time on my hands.

 

[Wonkydonkey]

Yeah, seems like most guys willing to share there numbers are right under 200. But then you got JMS running like 240 and hauling ass.
I'll try 190ish and see how it goes, new cylinder should be here friday.

Anybody try the exhaust lower than 100? 101 maybe?

Yeh I’ve read some peeps doin more than 200, but wasn’t it in one of those two strokin performance books, like yeh it may work for one race, then your be rebuilding it?

 

[brshephard]

Don't pay attention to anything JMS says, He can build a strong saw, but he also lies, so don't trust anything that comes from him.

I read about that halfass 064 he did for a member here. Seemed pretty crooked to me.
I bet he lost a lot more money in future sales than he ever saved cutting corners. Too bad.

 

[brshephard]

I’ve got one at 102/120/82 AM jug squish and base cut. Intake filled. Stock port widths. Runs decent with bridge ports. Working ports in stages to see individual gains.

I Do not know right from wrong in any way. Just got to much time on my hands.

Very cool, sounds like we're doing something similar.
Let me know how it turns out.

 

[Stihlmar]

It’s phat. Put the tach on it and it was only at 12k. Leaned it out to 12.8k. Really struggles To run big rpms. Holds 10k in the cut dawged in with the 32”. Work in progress!!

 

[brshephard]

I like it! I'd be curious to see how much rpm you gain when you widen the exhaust.
I had my saw at 13K no load with the timing set. I tuned it to 14.5 after widening.

Are you running full comp round?

Next time you're at the stihl dealer you should check out a 32" light bar. They're about like a 25" weight wise.

 

[Stihlmar]

You are correct on the chain. Rackers at .04.

I hope it starts to come along with some widening and maybe bring the exhaust up a few. Possibly add fingers. Been away from the garage. Getting busy at work.

Keep in touch on your build.

 

[brshephard]

You are correct on the chain. Rackers at .04.

I hope it starts to come along with some widening and maybe bring the exhaust up a few. Possibly add fingers. Been away from the garage. Getting busy at work.

Keep in touch on your build.

I hear ya on the work thing. I let let you know how mine turns out.

 

[Wonkydonkey]

I found this link, about compression and more heat generated, as well as knocking, not really sure if holds up to chainsaws. But it’s worth thinking /looking into. Maybe another reason why some chainsaws grenade

http://www.bridgestonemotorcycle.com/documents/higher_compression6.pdf