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Another chainsaw dyno...

Red97

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It's the nature of the carburetor. These little diaphragm carbs don't have an 'air bleed' jet in the high speed circuit to keep the proper fuel mixture after peak power.

I put an air bleed circuit in a Zama to try it and it revved like a motocrosser. Definitely needed a limited coil to keep from blowing it up.

Seems most other 2 strokes, bike,sled etc with a slide carb. The only thing keeping them from running away is load, then friction.

Where we can fuel a saw to not run away.

Have you tried tuning one on the dyno to find the peak power tune that way?

They are all set on the dyno, ad it has its own load and 84dl of chain.

The true max power does not change much. .05hp ish. From 1k extra rich to 1k lean.

The lean tune shows better power higher in the rpm range.

Other than maybe limbing i don't see any of the over rev power being super useful.

I like a tune you could process a whole bar length tree. Drop, top, and buck it all into firewood. 16k may be a little hot to do that with most any saw.

So is the 4
4 hp at 15.5k really going to do much? Not much tq at all at that rpm.
 

Nutball

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Seems most other 2 strokes, bike,sled etc with a slide carb. The only thing keeping them from running away is load, then friction.

Where we can fuel a saw to not run away.



They are all set on the dyno, ad it has its own load and 84dl of chain.

The true max power does not change much. .05hp ish. From 1k extra rich to 1k lean.

The lean tune shows better power higher in the rpm range.

Other than maybe limbing i don't see any of the over rev power being super useful.

I like a tune you could process a whole bar length tree. Drop, top, and buck it all into firewood. 16k may be a little hot to do that with most any saw.

So is the 4
4 hp at 15.5k really going to do much? Not much tq at all at that rpm.
Theoretically 4hp @ 15.5k should cut about twice as fast as a stock 60cc @8000rpm as long as wood cutting physics don't have a problem with that kind of chain speed.
 

Bigmac

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I think it’s more about the same saw tune to 12.5 vs 15.5 , In a large piece of wood we are loading the saw below 12,500 RPM it won’t make a difference, if you can’t load the saw to under 12,500 RPM in the wood because the wood is too small to soft or your chain isn’t set up correctly it will likely cut faster At the higher tune
 

Red97

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Theoretically 4hp @ 15.5k should cut about twice as fast as a stock 60cc @8000rpm as long as wood cutting physics don't have a problem with that kind of chain speed.

4hp at 15.5k is 1.4 ftlb. Not enough torque to cut anything sizeable without rpm drop.
 

huskyboy

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A 372 big bore 51.4 that’s a good one is gonna put some serious numbers out on that dyno for 5 cube. That is another saw that needs dynoed. I’ve ran a few that were something spectacular and others that were no faster or torquier than a 50mm. I think it’s in how they were ported...
 

Bigmac

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A 372 big bore 51.4 that’s a good one is gonna put some serious numbers out on that dyno for 5 cube. That is another saw that needs dynoed. I’ve ran a few that were something spectacular and others that were no faster or torquier than a 50mm. I think it’s in how they were ported...
It’s all in the porting! I think the tree monkey oh 66 is pretty good proof of that
 

ranchdadmike

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A 372 big bore 51.4 that’s a good one is gonna put some serious numbers out on that dyno for 5 cube. That is another saw that needs dynoed. I’ve ran a few that were something spectacular and others that were no faster or torquier than a 50mm. I think it’s in how they were ported...

I’d sure like to send mine..





(Sorry, can’t help myself[emoji23])
 
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