Stihl 660

[Allen Miller]

I'm thinking you are gonna have way too much compression

Been thank about taking .025 out of combustion chamber side. Also thought about making a copper shim for base. And raise cylinder up.

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[Allen Miller]

Do you have a degree wheel to measure the timing for us? I think your compression is a pretty big problem. I am also concerned with the timing if the cylinder after all the machining you did to it. It may be best to start over and take a much milder approach to modding this one. Its fun to play around but when they become so difficult to start and run poorly the fun is over. Before it gets pulled id love to see if the squish is even what the clearance us and what the timing is. Thank you for talking with us about your experiment.

Yes I have a degree wheel I have never used one on chainsaw before. been reading up on this. And your right this was an experiment figured I'd use a cheap cylinder before cut up a good mahle 066 cylinder I was shooting for 190psi when I was modify cylinder and piston .

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[brshephard]

I'm looking forward to seeing how this turns out.

When you get ready to check your port timing, Mastermind has a good video on setting a wheel up.

Numbers are read as: Exhaust/Transfers/Intake
Exhaust is read when the exhaust opens in degrees after top dead center (TDC)
Transfers are read when the upper transfers open in degrees after TDC
Intake is read when the intake port closes in degrees after TDC

You want to end up somewhere around 100/120/80

Here are a couple good threads:
http://opeforum.com/threads/mastermind-meets-the-ms660.244/
https://www.arboristsite.com/community/threads/066-ms-660-port-s-please-share-your-stock-s.263751/

 

[mdavlee]

Been thank about taking .025 out of combustion chamber side. Also thought about making a copper shim for base. And raise cylinder up.

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Open the chamber by making the band wider going into the chamber. Lewve squish at .022-024"

 

[drf256]

Been thank about taking .025 out of combustion chamber side. Also thought about making a copper shim for base. And raise cylinder up.

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Sorry, I don’t understand. Raising jug and then taking more outa the chamber won’t make the saw run well.

What squish now? You want a squish around 18-23 for chamber swirl and squish velocity. The charge left in the squish area doesn’t contribute to power, it’s lost charge.

If your squish is good now, just machine your popup dome down. If you cut your squish more, and drop jug more, you’ll just increase compression.

More isn’t always better for compression. Big saws like yours can’t dissipate heat like smaller saws can. Too much compression will lead to a saw that has increased bearing load, hard to start, low 4 stroking rpm and leans out in the cut as it heats up. Around 180-210 is the sweet spot for your size saw/model.

 

[Redfin]

You want to end up somewhere around 95/114/85

 

[brshephard]

Your best bet would be to shim up .075 and replace the piston.
This will get your compression down, fix your exhaust freeport, and fix your excessive intake duration all at the same time.

 

[Allen Miller]

Your best bet would be to shim up .075 and replace the piston.
This will get your compression down, fix your exhaust freeport, and fix your excessive intake duration all at the same time.

Relieved crankcase today. Put saw back together runs really well. No leaks around base. I guess everything I did wrong and for some reason will cut circle around my 066. So go figure you take your comments I'm shove them where the sun don't shine. Next time I'll do what ever body does and have the same saw. Like install a dual port mufler and base gasket delete. I appreciate 98 percent of comments and the post wear people tried to help but some people don't read from beginning and then make comments. I have learned a lot this week about port timing also using a degree wheel to check everything. And on compression I have a 044 10mm saw with 210psi and I that I built 3 years ago and I haven't had any problems with it and I used it about every weekend. Mastermind was right on his first comment and I would like to say thanks to him. I'll post all the numbers this week my degree wheel was to big in diameter. Order a 7inch one today. Also I bought two cross cylinder I'll post the stock one and the one I modified . Thanks

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[MustangMike]

I'm glad to hear your saw is running well, but calm down! I don't think anyone was trying to be mean.

Would love to see vids of it if you don't mind sharing.

 

[Wonkydonkey]

Thanks, That was a good thread,
https://www.arboristsite.com/community/threads/066-ms-660-port-s-please-share-your-stock-s.263751/
I don’t normally go looking there unless someone points me to something

Cheers.

 

[drf256]

Relieved crankcase today. Put saw back together runs really well. No leaks around base. I guess everything I did wrong and for some reason will cut circle around my 066. So go figure you take your comments I'm shove them where the sun don't shine. Next time I'll do what ever body does and have the same saw. Like install a dual port mufler and base gasket delete. I appreciate 98 percent of comments and the post wear people tried to help but some people don't read from beginning and then make comments. I have learned a lot this week about port timing also using a degree wheel to check everything. And on compression I have a 044 10mm saw with 210psi and I that I built 3 years ago and I haven't had any problems with it and I used it about every weekend. Mastermind was right on his first comment and I would like to say thanks to him. I'll post all the numbers this week my degree wheel was to big in diameter. Order a 7inch one today. Also I bought two cross cylinder I'll post the stock one and the one I modified . Thanks

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Anything commented was to try to help, not to criticize.

Learn from others mistakes and not your own.

Glad to hear it runs great. Could be even better, that’s the point. But sometimes a mistake can lead to a discovery.

Enjoy your saw and use good oil. Your squish at 10 will be great for swirl and velocity. I’m not sure if I would leave it there myself, but maybe I didn’t read the entire thread.

 

[cus_deluxe]

I guess everything I did wrong and for some reason will cut circle around my 066. So go figure you take your comments I'm shove them where the sun don't shine.

Seriously? You show up with a saw that doesnt run and your problem got solved. Nobody was tryin to hurt ur feelers there dude, just tryin to help. And those cross cylinders run better than a stock cylinder right outta the box, so that just means you didnt make it worse lol.

 

[drf256]

Seriously? You show up with a saw that doesnt run and your problem got solved. Nobody was tryin to hurt ur feelers there dude, just tryin to help. And those cross cylinders run better than a stock cylinder right outta the box, so that just means you didnt make it worse lol.

Stick it where the sun don’t shine Custer.

 

[Fruecrue]

Stick it where the sun don’t shine Custer.

Ain’t there a titanium wrist pin in there somewhere?

 

[brshephard]

Seriously? You show up with a saw that doesnt run and your problem got solved. Nobody was tryin to hurt ur feelers there dude, just tryin to help. And those cross cylinders run better than a stock cylinder right outta the box, so that just means you didnt make it worse lol.

Ha ha. Best answer

 

[huskihl]

Moron site......

 

[Fruecrue]

Moron site......

Bunch of ORPHANS

 

[smokey7]

Glad its running some things you did pushed the boundries of what most do for a long life saw engine. If squish is actually .010 and the motpr was rolled over several times (over 10 times over) you may be ok. Ive never gone tighter then .015 on a 50 cc saw. The bigger they are the bigger clearance you want as a rule. On a 90cc id shoot for .023-.025. I still would love to see sone of the timing nunbers and a complete comp test. Also was the jug hitting the case causing a air leak?

 

[brshephard]

Glad its running some things you did pushed the boundries of what most do for a long life saw engine. If squish is actually .010 and the motpr was rolled over several times (over 10 times over) you may be ok. Ive never gone tighter then .015 on a 50 cc saw. The bigger they are the bigger clearance you want as a rule. On a 90cc id shoot for .023-.025. I still would love to see sone of the timing nunbers and a complete comp test. Also was the jug hitting the case causing a air leak?

I tried a 660 with .010 squish. It looked like it had about .003 worth of squish band stamped on the piston.

I would guess .014" would be the absolute minimum for this saw.

 

[huskihl]

I tried a 660 with .010 squish. It looked like it had about .003 worth of squish band stamped on the piston.

I would guess .014" would be the absolute minimum for this saw.

Until the piston or band get some carbon on them