Fins Sexy Twins!!

[MillerModSaws]

It's crappy! Lol.

 

[blsnelling]

WTF?

I guess the rules don't alway apply. That's tight.

Carl, it's gonna be interesting to see the compression difference between the two saws. Were they run for the same amount so that ring breakin differences can be discounted?

Not really. I shoot for .018"-.020". My 066 came from the factory with .017". I know of another very well respected builder that built a 7900 with .012".

 

[blsnelling]

Why do you like it.

I see a trend towards tighter squish and lower compression amongst the builders here.

I've always aimed for 180-200 PSI compression. It doesn't take ultra high compression to make most saws run very well, and much less stress on the bottom end. Matter of fact, too much compression will slow some saws down.

 

[Andyshine77]

I've always aimed for 180-200 PSI compression. It doesn't take ultra high compression to make most saws run very well, and much less stress on the bottom end. Matter of fact, too much compression will slow some saws down.

Raising compression, without setting proper squish is counterproductive IMHO. In MOST true 70+cc work saws I don't want to see much over 180 psi of compression. The 7900 and a few others it's a necessity to make a good runner.

 

[SAWMIKAZE]

I've always aimed for 180-200 PSI compression. It doesn't take ultra high compression to make most saws run very well, and much less stress on the bottom end. Matter of fact, too much compression will slow some saws down.

I ran one that blew well north of 200psi that was a slug.

 

[SAWMIKAZE]

Raising compression, without setting proper squish is counterproductive IMHO. In MOST true 70+cc work saws I don't want to see much over 180 psi of compression. The 7900 and a few others it's a necessity to make a good runner.

A young man thats a 2 stroke nut that lives by me who i have taking an intrest in saws alot more now shares your opinion...along with his dad who's been diggin in these 2 smokers for 30 years , the 2 saws i have ported by those guys are no joke...they fast and torquey..so obviously theres some truth to it.

 

[MillerModSaws]

@mdavlee from the center of the piston pin to top of piston measures 28mm with a 12mm pin.

 

[Ironworker]

Raising compression, without setting proper squish is counterproductive IMHO. In MOST true 70+cc work saws I don't want to see much over 180 psi of compression. The 7900 and a few others it's a necessity to make a good runner.

Would you mind explaining what you mean by raising the compression without setting proper squish, do you mean making the squish too tight.

 

[MillerModSaws]

Overall length is 43mm. It's roughly 33mm from the bottom of the skirt to the flat on the side under the rings.

 

[Deets066]

Would you mind explaining what you mean by raising the compression without setting proper squish, do you mean making the squish too tight.

I would assume he meant not tight enough

 

[Andyshine77]

Would you mind explaining what you mean by raising the compression without setting proper squish, do you mean making the squish too tight.

I would assume he meant not tight enough

Correct.

 

[Ironworker]

Correct.

Now how do you go about knowing what tight enough is.

 

[Moparmyway]

It does for a 28" 8 rim. Lol. We will see how it likes a 36"

Were both videos with 8 tooth rims ?

 

[MillerModSaws]

Were both videos with 8 tooth rims ?

Yes sir.

 

[MillerModSaws]

Saw #1 back together at 100/118/81. No other changes.
Saw#2 muffler back off and ready to be made a dual port.

Excited to see how they stack up! That is if it ever quite fricking raining here!

Hey @fin460 wanna come mud me to a tree. I'll bring the beverages!

 

[fin460]

I only have a couple days of wood left, I have to cut soon

 

[drf255]

Now how do you go about knowing what tight enough is.

The squish amount does a few things.

It adds turbulence to the charge, so you SHOULD be less detonation resistant.

Also, the volume tapped in the Squishband isn't burned during the essential part of the power stroke. So that volume of charge is lost.

When there is expansion of the piston when the heat builds up, the squish area tightens more than the measured amount on the workbench. If the piston hits the jug at 10,000+ rpm, bad **** happens.

From hat I've seen here, the minimum amount varies and is predicated to some extent by the model, displacement and the quality and tolerances of the machine work.

My latest 026 was at .014, but I opened to .020 for comfort. It's already pulling 240 psi at .020.

From what I'm reading here, I should drop the jug down to .016 and open my chamber by a beveling it where it interfaces with the band.

 

[MillerModSaws]

Alright this isn't a very good comparisson but the first saw up is the 83 intake second saw up is the 81 intake. I havnt timed them but I'm guessing that's almost pointless as I probably didn't stop in the same spot twice. Lol.

 

[MillerModSaws]

Justin came and grab the saws tonight so he will do further testing and we'll get a tach on them when it gets here. First impression is the higher intake saw is torqueier but the both need some run time to let the mtronic reset and we'll go from there. Both running the same b&c 8 rim 36".

 

[blsnelling]

Did you feel the additional muffler work made a difference?