288 Piston in a 660

[Vintage Engine Repairs]

Nice mate, top work as always!!

 

[drf256]

Bought an AM rear cover to hack up for some airflow.

The coating on the bottom of the piston is pristine, but is seems that some came off near the ring land area. Can see machine marks, so all good.

My exhaust roof looks a bit too safe, but it’s damn wide.

The MAGNUM sticker has to worth 2% easy.

Played w the carb a bit too. Hope to cut Sunday.

 

[drf256]

Skirt pics. The “whoops” a did when the burr jumped on me is still on the skirt.

 

[drf256]

Wasn’t entirely happy with how the saw was running, so I went back into it. This is the piston after one tank.

Imagine the coating normally wears off?

I widened exhaust, flattened the roof, and change the timing of all 4 ports.

Vids to follow, likely this weekend.

 

[Maintenance Chief]

Yes, its like moly coating you camshaft, meant for break in.
Is the swirl pattern too far foward on the piston?

 

[Vintage Engine Repairs]

What oil are you running there mate?

 

[drf256]

It’s just under a tank of Dominator in Efree 89 at 32:1

I think the pattern is pretty good. The issue is saw port geometry and the fact that the Stihl 660 jugs are sow’s ears.

 

[drf256]

Reworked roof, uppers and intake. HOPE to run tomorrow.

Believe it or not, the front of the big sloppy upper is square.

 

[rogue60]

That saw has the good heavy 066 clutch shoes. The lighter ms661 clutch shoes and springs are very noticeable in throttle response and fast spool up.

 

[rogue60]

Here you can see how much they lightened the ms661 clutch shoes compared to a ms660 clutch. Also the ms661 springs are heavier and engage at a higher rpm.

 

[drf256]

another pic of redone ex roof.

 

[NateSaw]

another pic of redone ex roof.

View attachment 384415

Lack of experience... Clearly it isn't a problem or you guys doing hybrids wouldn't do it.... But that ring gap in the exh port makes me noivous

 

[Vintage Engine Repairs]

Like a surgeon, well done mate!

 

[drf256]

 

[Powerstroke Cowboy]

Very nice! What rpms was it producing in the cut? Sounds like it was reving up pretty good. Wild guess. 11,500 to 12,000? Maybe my ear needs recalibrated?

 

[Maintenance Chief]

Impressive amounts of torque! Are you running full comp?
Looks great in the cut.

 

[drf256]

Full comp 404. Stihl RS. 7T

It held 10500-11200 in the cut. More with the slower rpm fatter tune. Piss revving, I was anywhere from 13200-14000.

Most work saws make more power in the cut with a fatter tune. Especially with wood that loads them, like this dry white oak.

 

[Powerstroke Cowboy]

Full comp 404. Stihl RS. 7T

It held 10500-11200 in the cut. More with the slower rpm fatter tune. Piss revving, I was anywhere from 13200-14000.

Most work saws make more power in the cut with a fatter tune. Especially with wood that loads them, like this dry white oak.

My ear needs recalibrated. It looks like it
cuts nice!

My clone 880 that I ported runs better fat as well. I tuned it by running up to max rpm, then I backed it off till it was 4-stroking then made it a little fetter for break in. It ran good, but not in the cut. Se saw wanted to buck a little it didn't cut nice and smooth. So.Ingave it more fuel, the rpms out of the cut dropped, but the rpms in the cut went up. She stopped bucking and ran nice and smooth in the cut.

 

[Maintenance Chief]

I thought those were big chips , she's a winner in my opinion.

 

[drf256]