Another chainsaw dyno...

[Red97]

By who?

Also, do we have a baseline for a stock one?

Miller mod saws

 

[Red97]

Sticker says same fella that did the Dolly

Yep

261c v2
5105
6100

All ported

 

[MustangMike]

See that, and I was thinking they were all real strong for stock!!!

That puts things in perspective as to why they all handily beat advertised Hp.

 

[cuinrearview]

To me, everything has looked pretty consistent with advertised specs and expectations.

 

[jacob j.]

That was a ported 261c

Yah, but was it a "new recipe" ??

 

[David Young]

Yah, but was it a "new recipe" ??

Always the best.

 

[Deets066]

Yah, but was it a "new recipe" ??

New doesn’t always mean better...

Ever make chili????

 

[mdavlee]

Yep

261c v2
5105
6100

All ported

What impressed me is the peak on the 5105 is at 11k.

 

[Redfin]

New doesn’t always mean better...

Ever make chili????

The jest, you missed.

 

[Deets066]

The jest, you missed.

I sawed it

 

[Redfin]

Was it worth your time or the risk?

 

[Deets066]

Was it worth your time or the risk?

Not at all

 

[Red97]

Picked the low hanging fruit.

Gasket delete, cut band .028
Move the ex, and transfers
Little muffler mod .

 

[mdavlee]

Picked the low hanging fruit.

Gasket delete, cut band .028
Move the ex, and transfers
Little muffler mod .

View attachment 246247 View attachment 246248

So 40%? [emoji23]

 

[Red97]

So 40%? [emoji23]

Maybe 6%?

 

[Terry Syd]

I wonder if the irregular power curve up in the revs is a result of reed valve 'flutter' on the 6100.

A change in reed material or thickness might change the curve.

I always wanted to see how a different set of reeds would affect the 6100. I suspect the factory may have found a particularly strong running set of reeds, but the reeds could have been too fragile for commercial sales and it would reflect poorly on the 6100s reliability.

If I ever get one of those puppies, I'd go with a bigger carb and thinner reeds with probably a lower reed stop.

EDIT: Was the 'limiter jet' in the carburetor's low speed circuit enlarged?

 

[Red97]

I wonder if the irregular power curve up in the revs is a result of reed valve 'flutter' on the 6100.

A change in reed material or thickness might change the curve.

I always wanted to see how a different set of reeds would affect the 6100. I suspect the factory may have found a particularly strong running set of reeds, but the reeds could have been too fragile for commercial sales and it would reflect poorly on the 6100s reliability.

If I ever get one of those puppies, I'd go with a bigger carb and thinner reeds with probably a lower reed stop.

EDIT: Was the 'limiter jet' in the carburetor's low speed circuit enlarged?

That one was being very picky. I do believe the second peak in the graph, is indeed a load spike.

Was being difficult to get a nice smooth run.

 

[Terry Syd]

With your set-up, it would be cool to have a couple of reed blocks and a selection of reeds. Try one set, then another, while the second run was going, change the reeds on the first block, then swap reed blocks again.

After a few runs you'd get a good idea which reeds were going to produce the most power. Or, what modifications might be made to a set of reeds, say, a shorter reed backing a full length reed to limit flutter at RPM.

 

[Bigmac]

I wonder if the irregular power curve up in the revs is a result of reed valve 'flutter' on the 6100.

A change in reed material or thickness might change the curve.

I always wanted to see how a different set of reeds would affect the 6100. I suspect the factory may have found a particularly strong running set of reeds, but the reeds could have been too fragile for commercial sales and it would reflect poorly on the 6100s reliability.

If I ever get one of those puppies, I'd go with a bigger carb and thinner reeds with probably a lower reed stop.

EDIT: Was the 'limiter jet' in the carburetor's low speed circuit enlarged?

In Mx style motors like dirt bikes, if the reed material is thick it will allow it to rev better, if it’s too thin it will make great power down low and then hit an rpm wall and the power fall of hard! It’s weird but it’s basically that too thin of reed material will just hang open and fuel will go back through the carb reducing the case compression, so a stiff reed should rev better, I know there is balance, but it shouldn’t cause the dips in the upper rpms

 

[Terry Syd]

if the reed material is thick it will allow it to rev better, if it’s too thin it will make great power down low and then hit an rpm wall and the power fall of hard!

Exactly! The 6100 has a dual intake system. The carburetor intake is piston ported. I have noticed in the EPA saws that the carburetor is usually small and the fresh air intake is a bit larger. I expect that is to promote less emissions. That's why I said I would use a bigger carburetor, to MAXIMIZE the carburetor intake - make use of the 'gulp factor' of the piston port intake.

When it comes to reed intakes, at low RPM the reeds work more like a rotary valve engine and give great low end power. However, at high RPM the reeds have a 'timing' (because of their mass that slows things down) that is closer to a piston port engine. A thinner reed allows more flow down low, but tends to flutter at higher speeds.

Back in the 1970s Suzuki had a reed in the piston port carburetor intake. That may have helped at very low RPM, but the biggest problem was that once the piston opened the port the low pressure across the reeds stopped and became useless.

The 6100 doesn't have that problem as the two systems are separate. The reed system can be open and continue to flow when the piston port opens.

Thus, the piston port intake with a larger carburetor could provide the flow needed for high RPM and a thin reed system (with appropriate reed stops or proper reeds) could provide extra flow at lower RPM.

With the carburetor set up to provide a bit more fuel flow in the low speed circuit when the thinner reeds were flowing well, the result could be a much broader powerband.