090 Stihl ??????

379 pete · 03-06-2008, 08:59 PM

Hi, I recently tore down an 090 Stihl for a rebuild, The crankshaft has 2 weights added to the crankshaft counterweights, look like they were TIG welded on, and are Not factory. Is there anybody out there that can explain how balancing works, Was this done to compensate for a heavier piston or higher RPM's???? I didn't get the piston or jug with the saw, so I don't know what they had for a top end on this case. I would like to reuse the crankshaft, but don't know how it will act with a stock piston. I am thinking that this was an attempt to build a Hot Saw at one time. Any help would be great. Thanks/379 Pete

slabmaster · 03-09-2008, 03:53 PM

Interesting.That would be for balancing.Is the crank knife edged? That would be the most likely reason they are there.To make up weight that was taken off the crank.Do you have a picture?Are they inserted into the sides of the counterweights? Usually a hole is drilled and heavy metal slugs are inserted.Hope this helps,Mark

379 pete · 03-09-2008, 08:53 PM

Thanks Mark, Its really strange, the crank looks totally stock except for the two weights added. They are about 3/16" thick and are welded to the insides of the counterweights, leaving just enough room for the rod to pass thru. Some of the older 070 & 090 crankshafts had similar weights that bolted in with countersunk allen bolts, but this is a newer crank that didnt use that system. The only ideas I can come up with is that it was done to gain a higher RPM, the stock engine was governed to 7000 RPM max. or to compensate for a lot bigger heavier piston??? I just dont know all that much about how balance in an engine works. I can get pictures, if I can figger out how to post them. Thanks/379 Pete

Bill G · 03-09-2008, 10:07 PM

Here is a new 090 crank I pulled off the shelf. Does it look like this?

Bill

379 pete · 03-09-2008, 10:16 PM

Hi Bill, The weights are built like that, But they are welded in, and there are no drilled holes for the bolt on type weights. There is about 4 or 5 different crankshafts that were over the span of the 090. The newest style is like the 066 ect. and are pressed together, yours is the older forged 1 piece. Its got me stumped. Thanks for the reply/379 Pete

Bill G · 03-09-2008, 10:18 PM

Please post some pictures. I have 090 saws of various ages so I would like to see what you have.

Sincerely,
Bill

379 pete · 03-09-2008, 10:31 PM

Hi Bill, I looked closer at you picture, I think thats the new style thats pressed together with the one piece rod. Mine is the older style with the two piece rod. I will get some pics. later. Thanks/379 Pete

379 pete · 03-10-2008, 07:15 PM

Pictures of crankshaft

Bill G · 03-10-2008, 10:10 PM

Quote:

Originally Posted by 379 pete

Pictures of crankshaft

I would personally not run that crank. It looks like a accident waiting for a saw to occur in. I am sure other will weigh in but that looks like a "backyard fix"

Bill

ozflea · 03-10-2008, 10:56 PM

Mac did the same thing on their SP125C saws to ease vibration frst were glued and screwed second lot welded to stop crank failures

Macmuncher · 03-11-2008, 02:12 AM

My 20 cents say that they were welded in to increase crank case pressure, normally only for racing applications where the saw did not run long.

slabmaster · 03-11-2008, 06:05 AM

Quote:

Originally Posted by Macmuncher

My 20 cents say that they were welded in to increase crank case pressure, normally only for racing applications where the saw did not run long.

I agree.That is a racing mod.Done to lower crankcase volume,increasing presure for higher rpms.I don't think it would be good for a work saw though. Mark

379 pete · 03-11-2008, 09:37 AM

Thanks Guys, That makes the most sense I have heard yet, Lower crankcase volume !!!!! Somebody put some time into doing the modification. The saw came from Washington state, does anybody recognize their work ??? Think I should put it in, add a snowmobile carb., unhook the governor, see how it acts at 12,000 RPM ????? 379 Pete

Dibbs · 03-11-2008, 03:41 PM

Quote:

Originally Posted by 379 pete

Think I should put it in, add a snowmobile carb., unhook the governor, see how it acts at 12,000 RPM ????? 379 Pete

If you want to see a heavy Steel Flywheel leave your saw through the crankcase then that is the best way to do it!

olyman · 04-03-2008, 06:25 PM

Quote:

Originally Posted by Dibbs

If you want to see a heavy Steel Flywheel leave your saw through the crankcase then that is the best way to do it!

and what 090's are worth---------------N O T !!!!!!!!!!!

03-06-2008, 08:59 PM	#1
379 pete Junior Member Join Date: Apr 2006 Location: North Branch, MN 55056 Posts: 28	090 Stihl ?????? Hi, I recently tore down an 090 Stihl for a rebuild, The crankshaft has 2 weights added to the crankshaft counterweights, look like they were TIG welded on, and are Not factory. Is there anybody out there that can explain how balancing works, Was this done to compensate for a heavier piston or higher RPM's???? I didn't get the piston or jug with the saw, so I don't know what they had for a top end on this case. I would like to reuse the crankshaft, but don't know how it will act with a stock piston. I am thinking that this was an attempt to build a Hot Saw at one time. Any help would be great. Thanks/379 Pete __________________ Homelites - C-71, C-9, C-91, XL12's lots of em, Sthils 009, 170, 024, 028, 034, 038. MS 440, 064, 066, MS 660, S-10, 090, 070, Contra Lightning

03-09-2008, 08:53 PM	#3
379 pete Junior Member Join Date: Apr 2006 Location: North Branch, MN 55056 Posts: 28	Thanks Mark, Its really strange, the crank looks totally stock except for the two weights added. They are about 3/16" thick and are welded to the insides of the counterweights, leaving just enough room for the rod to pass thru. Some of the older 070 & 090 crankshafts had similar weights that bolted in with countersunk allen bolts, but this is a newer crank that didnt use that system. The only ideas I can come up with is that it was done to gain a higher RPM, the stock engine was governed to 7000 RPM max. or to compensate for a lot bigger heavier piston??? I just dont know all that much about how balance in an engine works. I can get pictures, if I can figger out how to post them. Thanks/379 Pete __________________ Homelites - C-71, C-9, C-91, XL12's lots of em, Sthils 009, 170, 024, 028, 034, 038. MS 440, 064, 066, MS 660, S-10, 090, 070, Contra Lightning

03-09-2008, 10:16 PM	#5
379 pete Junior Member Join Date: Apr 2006 Location: North Branch, MN 55056 Posts: 28	Hi Bill, The weights are built like that, But they are welded in, and there are no drilled holes for the bolt on type weights. There is about 4 or 5 different crankshafts that were over the span of the 090. The newest style is like the 066 ect. and are pressed together, yours is the older forged 1 piece. Its got me stumped. Thanks for the reply/379 Pete __________________ Homelites - C-71, C-9, C-91, XL12's lots of em, Sthils 009, 170, 024, 028, 034, 038. MS 440, 064, 066, MS 660, S-10, 090, 070, Contra Lightning

03-09-2008, 10:31 PM	#7
379 pete Junior Member Join Date: Apr 2006 Location: North Branch, MN 55056 Posts: 28	Hi Bill, I looked closer at you picture, I think thats the new style thats pressed together with the one piece rod. Mine is the older style with the two piece rod. I will get some pics. later. Thanks/379 Pete __________________ Homelites - C-71, C-9, C-91, XL12's lots of em, Sthils 009, 170, 024, 028, 034, 038. MS 440, 064, 066, MS 660, S-10, 090, 070, Contra Lightning

03-10-2008, 10:56 PM	#10
ozflea Arboristsite MVP Join Date: Dec 2004 Location: New South Wales Australia Posts: 1,145	Mac did the same thing on their SP125C saws to ease vibration frst were glued and screwed second lot welded to stop crank failures __________________ The one eyed Mac Man The thunder from downunder Australian McCulloch Racing Chainsaws http://macbobaust.com/saws.html "All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident." "Thats why you should have gotten a Mac First" Bob Cornwell.....

03-09-2008, 03:53 PM	#2
slabmaster Arboristsite MVP Join Date: Feb 2008 Location: Mi. Posts: 555	Interesting.That would be for balancing.Is the crank knife edged? That would be the most likely reason they are there.To make up weight that was taken off the crank.Do you have a picture?Are they inserted into the sides of the counterweights? Usually a hole is drilled and heavy metal slugs are inserted.Hope this helps,Mark

03-09-2008, 10:18 PM	#6
Bill G Arboristsite MVP Join Date: Mar 2002 Location: Illinois Posts: 4,795	Please post some pictures. I have 090 saws of various ages so I would like to see what you have. Sincerely, Bill

03-11-2008, 02:12 AM	#11
Macmuncher Member Join Date: Mar 2007 Location: Under the gum leaves! Posts: 40	My 20 cents say that they were welded in to increase crank case pressure, normally only for racing applications where the saw did not run long.

03-11-2008, 09:37 AM	#13
379 pete Junior Member Join Date: Apr 2006 Location: North Branch, MN 55056 Posts: 28	Thanks Guys, That makes the most sense I have heard yet, Lower crankcase volume !!!!! Somebody put some time into doing the modification. The saw came from Washington state, does anybody recognize their work ??? Think I should put it in, add a snowmobile carb., unhook the governor, see how it acts at 12,000 RPM ????? 379 Pete __________________ Homelites - C-71, C-9, C-91, XL12's lots of em, Sthils 009, 170, 024, 028, 034, 038. MS 440, 064, 066, MS 660, S-10, 090, 070, Contra Lightning

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