2- MS660 Arctics + 1-MS660

dastevoe

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Jan 10, 2012
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Hey guys, here's my dilema......... I have (2) MS 660 Arctics & (1) MS660 to work over. One Arctic is mine & the other 2 belong to a buddy who runs a tree service. I haven't got the timing off of them yet but recall some of you saying the 660's are not as good as the old 066's. What have you guys found to be the best "recipe" for these 660's ? Are you cutting the combustion chambers & if so what #'s are you getting ?
Tree monkey........ Mastermind.........JJ........Nitrosaws gang, any help is appreciated :thumbsup:

Steve
 

dastevoe

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Jan 10, 2012
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Thanks Rick. I tried to fire up one of the TT (tree trimmers) saws last night & "no poppy", checked compression ...... 95# :sad: pulled the muff & this is what I found 021.jpg024.jpg:throwup:

I am pretty sure he wants to try a BB kit on this one. Has anyone used the kits from Northwoodsaw ???

Steve
 

mweba

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Jan 10, 2012
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Yes, I haves several 372bb's out and one 660. I liked the plating and port shape was leaps better than NPW. Port shape was the reason I gave them a go in the first place...of course you will be changing the shape:yup:
 

dastevoe

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Jan 10, 2012
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Yes, I haves several 372bb's out and one 660. I liked the plating and port shape was leaps better than NPW. Port shape was the reason I gave them a go in the first place...of course you will be changing the shape:yup:
Was the 660BB a Northwoodsaw kit too ? If so sounds good as Sal ships fast & cheap to Canukistan :smoking:

Any BB piston swaps out there ? If not I guess a set of Caber rings will be in order too.

So what is the verdict on cutting the squish on these as well as the 660 stock jugs ?

Steve
 

mweba

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Jan 10, 2012
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Yes it was. No experience cutting the base on one but the kit rings have run thus far. The cir clips were better than the normal am kit as well. Interested to see what you come up with.
 

jacob j.

When I let my hair down, my friends call me Dick C
Jan 9, 2012
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The Northwood saw 660 BB kit still has a fairly flat roof on the exhaust port that has to be dealt with.
I would still stay away from using the wrist pin and clips in those as well. I used OEM Husky 372 pins and clips
in the last three I built. The good thing about the Northwood kits though was no "black ring of death" at the
squish band. The 660 case will require some clearance work most likely. I always do mine after I split the case
and pop the old bearings and seals out. If I'm doing the BB kit the saw gets new bearings even if the old
ones weren't shot unless it's an extremely low hour saw with a known history.

Other builders have already posted about the Stihl 660 cylinders having too much exhaust timing and that's been
my experience as well. Too much exhaust timing and tall blow down numbers. The old Red Light saws had about
the best timing numbers I've run into with any of the 066/660 saws.
 

dastevoe

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Jan 10, 2012
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The Northwood saw 660 BB kit still has a fairly flat roof on the exhaust port that has to be dealt with.
I would still stay away from using the wrist pin and clips in those as well. I used OEM Husky 372 pins and clips
in the last three I built. The good thing about the Northwood kits though was no "black ring of death" at the
squish band. The 660 case will require some clearance work most likely. I always do mine after I split the case
and pop the old bearings and seals out. If I'm doing the BB kit the saw gets new bearings even if the old
ones weren't shot unless it's an extremely low hour saw with a known history.

Other builders have already posted about the Stihl 660 cylinders having too much exhaust timing and that's been
my experience as well. Too much exhaust timing and tall blow down numbers. The old Red Light saws had about
the best timing numbers I've run into with any of the 066/660 saws.
Thanks JJ, I have the 660 (non-arctic), torn down & put the wheel on it. Found the ex. 96* (168* dur) , int. 81* (161* dur), and transfers 121* (118* dur).
I was thinking of cutting the squish to get 100* ex., that would move my int. to 85* & trans. to 125*. Where do these #'s fall in comparison to the Red Light saws ? I'm guessing the transfers on the RL would be higher, in the 118* zone ???
As a bonus of cutting the squish I'll reduce the combustion chamber & bump up the compression.

Steve
 

mdavlee

How the heck did this take so long?
Jan 10, 2012
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The 066 I did for the build off had .040" cut from the chamber and base. Squish was .024" and compression is 180 on it. It was a mahle with de comp and the exhaust is 99, transfers 118, and intake was 82. It seems to run real nice with those numbers.
 

dastevoe

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Jan 10, 2012
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I did some measuring & noticed this (Stihl), jug isn't honed completely up to the squish, borderline "ring of death" scenario. I have another scrapped Stihl labeled jug & it also appears that way too !! Are you guy seeing this in the jugs you're cutting combustion chamber/ squish band ?? I have seen where some cut as much as 1.5mm (.060") , on mine I am at the absolute top edge of the top ring If I cut out .030" & remove the base gasket & cut .018 off of the base. Fortunately this will put me right on my 100* exhaust number, maybe I'm worrying overly about that top ring into the "no-go zone"..........
Are the Mahl jugs finished right up to the squish ?
Interesting about using a 288 piston !!!!!! I'll have to have a peek at one I have here !!
Thanks for sharing, keep it coming.

Steve
 

komatsuvarna

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I know some use a 066 piston in a 288. If I have it right, you can machine a big ole popup on the 066 piston, and use a base gasket and have about 210psi in a 288. So the 066 piston must be taller. I guess a 288 piston would allow you to get the exhaust on down there on the newer 660 jugs that have 170+ degrees of exhaust duration.....but Im just thinking out loud too. Bet the intake would be on up there unless the skirts is longer. May have to check into that......:)
 

Wigglesworth

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Jan 9, 2012
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I did some measuring & noticed this (Stihl), jug isn't honed completely up to the squish, borderline "ring of death" scenario. I have another scrapped Stihl labeled jug & it also appears that way too !! Are you guy seeing this in the jugs you're cutting combustion chamber/ squish band ?? I have seen where some cut as much as 1.5mm (.060") , on mine I am at the absolute top edge of the top ring If I cut out .030" & remove the base gasket & cut .018 off of the base. Fortunately this will put me right on my 100* exhaust number, maybe I'm worrying overly about that top ring into the "no-go zone"..........
Are the Mahl jugs finished right up to the squish ?
Interesting about using a 288 piston !!!!!! I'll have to have a peek at one I have here !!
Thanks for sharing, keep it coming.

Steve
I wouldn't cut the chamber on a stihl branded jug. I have one in the shop that the "ring of death" is probably close to .200 down. Its the worst ive seen. Im not sure how it didnt hang a ring up there....

All of the mahle ive seen were finished all the way up.
 

MacLaren

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Jan 9, 2012
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I wouldn't cut the chamber on a stihl branded jug. I have one in the shop that the "ring of death" is probably close to .200 down. Its the worst ive seen. Im not sure how it didnt hang a ring up there....

All of the mahle ive seen were finished all the way up.
Wow. Thats certainly not good. A lot of Stihl branded cylinders out there. Mine included. Im not sure how much Scott cut from it though. It hasnt had any problems yet. But I hear ya Wiggz, and certainly believe ya too. Thnx for the 411
 

HEAVYFUEL

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I know some use a 066 piston in a 288. If I have it right, you can machine a big ole popup on the 066 piston, and use a base gasket and have about 210psi in a 288. So the 066 piston must be taller. I guess a 288 piston would allow you to get the exhaust on down there on the newer 660 jugs that have 170+ degrees of exhaust duration.....but Im just thinking out loud too. Bet the intake would be on up there unless the skirts is longer. May have to check into that......:)
Hey Durand, I'm not trying to say 288 is stronger, just throwin options out there. At the time I had it done it was just an option for me & I wanted to try something different. Like Eric said end result is prolly the same.
 

komatsuvarna

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Hey Durand, I'm not trying to say 288 is stronger, just throwin options out there. At the time I had it done it was just an option for me & I wanted to try something different. Like Eric said end result is prolly the same.
Ooh I know John, just thinking out loud.....pay no attention to me.:):banana:
 
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dastevoe

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Jan 10, 2012
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Here is the latest on this project. I got the Northwoodsaw BB kit & the transfers were "miniscule", had to open & widen them BIGTIME to come even close to the OEM jugs. Ex. freeported at the bottom of the piston at TDC by ~.020" :ahah: So after "fixing" the transfers & opening the piston windows I put Caber rings on & assembled w/out base gasket+ MM. Runs well............ lotsa torque, definately not a screamer. I won't buy another NWoodsaw BB kit though. This was supposed to be just a bolt on fix :(
The non-arctic is a different story :D, cut the comb/squish straight for~2mm then tapered it 2* & lost the gasket to get .020" squish, only needed to cut about.015" out (I wouldn't go any more anyway because of the "ring of death"), added Cabers, woods port, piston windows milled etc. & MM mod., advanced timing 1/2 the flywheel key ( I wish I had measured how much in *'s that was, I don't like doing things blindly but was anxious to get it done). This is a nice running saw !!! There is a lot to be said for OEM.
Has anyone found A/M 066/660 kits that are close to OEM ???

Steve
 
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naked arborist

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Merica kinda... So. Joisey
Has anyone found A/M 066/660 kits that are close to OEM ??? Steve[/QUOTE said:
Yes.

The piston is a bit longer also. I will be working through the numbers today. Your not going to believe the size if the transfers. The jug has a better factory finish in the ports than an OEM. Only shortcoming I see is the flat exhaust roof. The roof came in at 96 last night and the squish is 030 gasket delete. This piston should be the fix for free porting on OEM type jugs after they are dropped. Exhaust duration looks like 168 with a high floor. Top of hole, the band is wider and the pocket looks to be smaller.

The OEM jug was just showing the AM crown and put up the same numbers. Granted that OEM jug has the right or better exhaust port shape. This one should be very interesting.
 
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