Lakeside53
Stihl Wrenching
???
066 Magnum Big Bore Project
- Thread starter blsnelling
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2000ssm6
Stihl User
???
I'm just wondering what Gumnuts is referring to about the MS crank. This is a later model poly flywheeled 066 Magnum, so it has the larger crank stub and bearing on the flywheel side.
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Some people think that the cranks were beefed up when the model designation went to the "MS" series, but of course the cranks were beefed up long before then...
Gumnuts
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Were they.Not what my Stihl tech( supervisor State HQ ) told me.
Mines a 2002 Mag that was rebuilt, i was told ,with larger MS crank
Guess thats another good reason to be here.Only believe half of what i'm told by workshop.Bad experiences with BSh$$ from them.
Mines a 2002 Mag that was rebuilt, i was told ,with larger MS crank
Guess thats another good reason to be here.Only believe half of what i'm told by workshop.Bad experiences with BSh$$ from them.
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I have on 066 that I got from AS member Thompson1600. I put the BB kit on it, but needed to do some significant modification to the crankcase to get clearance for the piston at BDC. Timberwolf documented a similar situation with his BB installation, so I was on the look out for the same problem when I went to install mine. Sure enough, I did a loose assembly and couldn't turn the engine over. So, I got the grinder out and cleared out some metal.
It runs pretty well now. I only have about 5 tanks through it, so there still may be some gains. I'll try to remember to get some numbers from it in a week or two once I can run more fuel through it.
I can tell you that it pulls a 32" bar with full comp round ground Oregon chain through hard maple and red oak with no trouble spinning a 7 tooth gear.
It runs pretty well now. I only have about 5 tanks through it, so there still may be some gains. I'll try to remember to get some numbers from it in a week or two once I can run more fuel through it.
I can tell you that it pulls a 32" bar with full comp round ground Oregon chain through hard maple and red oak with no trouble spinning a 7 tooth gear.
Was this a recently purchased kit? I did nothing but bolt the kit on and run it.
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Freakingstang
Doctor Freakinstein
I'm wondering if the older metal flywheel cases had less clearance?????
The piston skirts are considerable shorter on the BB kit than OEM. Something like 1/8". I did not measure. Have they always been this way or was this done to simplify installation?
Lakeside53
Stihl Wrenching
I'm betting it was a quick and dirty way out of the case fit issues...
From where i sit, sounds like you got a bit lucky. Free port wood mess up everything.
man o man it is wild here in Lawrence. Guns, fireworks, screaming, helicopters, airplanes, I oughta shoot offa gun or two, except I hafta be at work in less than 8 hours. o well
WTF KU WINS! HAHA
That's not what I'm told by a builder that uses these. He even proceeds to do a popup piston which causes an additional .035" of free port. Still idles and runs great. The key is to open up the muffler enough that the pressures are equalized.
I think I got one of the earlier released kits where skirt/case clearance was an issue. I agree with Lakeside that shortening the skirt (who could argue with that!) was a way to solve the problem.
I remember a discussion here as to whether a very slight opening of the crankcase at TDC (due to a too short skirt) would be a problem.
If there's a positive pressure wave heading back to the piston that arrives a degree or two before TDC as the skirt is clearing the bottom of the exhaust port, then perhaps there could be a slight pressurizing effect in the crankcase. However, a negative pressure wave could suck part of the charge right out of the case, leaving less fuel to power the next cycle. So, maybe it's an rpm dependent phenomenon.
Timberwolf, where are you, we need you here!!
I remember a discussion here as to whether a very slight opening of the crankcase at TDC (due to a too short skirt) would be a problem.
If there's a positive pressure wave heading back to the piston that arrives a degree or two before TDC as the skirt is clearing the bottom of the exhaust port, then perhaps there could be a slight pressurizing effect in the crankcase. However, a negative pressure wave could suck part of the charge right out of the case, leaving less fuel to power the next cycle. So, maybe it's an rpm dependent phenomenon.
Timberwolf, where are you, we need you here!!
OK. Thanks, I really didnt know, I just thought it wood mess up the impulse line pressure and throw the whole fuel delivery system on its face. Don't send yoiur saws to me for race builds just yet....... I am still on the butt end of the learning curve!:monkey: :greenchainsaw: :greenchainsaw: :greenchainsaw:
I don't know this stuff either. Just passing along what I've been told.
Freakingstang
Doctor Freakinstein
I was always under the assumption tha the term free port meant side clearance, as in making the port wider than the piston skirt....
As far as the cranks are concerned, mid 97' (lakeside and jacob can correct me if I am wrong) is when they changed to the heavier duty cranks and poly flywheels. If it has a metal flywheel it is the smaller crank. I have an older version (looks like an old redlight, but is a crossover with the decomp and poly flywheel/heavier duty crank.
I also don't believe they put the MS title on them before 03 (in the ms 660 line). My first 066 was an really early 03 model and was an 066 instead of the MS 660....
As far as the cranks are concerned, mid 97' (lakeside and jacob can correct me if I am wrong) is when they changed to the heavier duty cranks and poly flywheels. If it has a metal flywheel it is the smaller crank. I have an older version (looks like an old redlight, but is a crossover with the decomp and poly flywheel/heavier duty crank.
I also don't believe they put the MS title on them before 03 (in the ms 660 line). My first 066 was an really early 03 model and was an 066 instead of the MS 660....
Lakeside53
Stihl Wrenching
nothing to correct!
When did they changed the case to make it longer, to fit the case gasket that comes in the gasket kit. My 066 Magnum has the larger crank and poly flywheel, but uses the same case gasket as my 066 RL. Was anything else changed at that time? Is my plastic the same as a 660?
Lakeside53
Stihl Wrenching
Apart from the model plate, yours is basically the same as a 660... and uses the same plastic.
What about the case gasket difference? Mine required a 1122 029 0500 gasket, same as the RL.
