Bottom end bearing/crank/case problem

[Old Crosscut]

Just finished installing new bearings, bottom end, on an 028. Now, I’m unable to get the crank to turn freely, at least as freely as I think it should.
Assembly procedure: Froze the crank, warmed the bearings on top of my wood stove. A few taps, long socket/washers, and the bearings easily bottomed on the crank. Froze the crank and bearings, warmed both case halves on my wood stove. Again, a few taps with a long socket/washers over the flywheel side easily seated the outer bearing race against the C-clip on the clutch side. The flywheel side went together easily, also, to within a quarter-inch closure--by the same method. I had the alignment pins set to protrude only an eight-inch or so, and the cases pulled the remainder of the way together with only minimal torque applied to the case bolts. The flywheel side outer bearing race popped a few times while pulling the cases together, then the pins drove on in and the bolts torqued down just fine. All seemed right with the world.
At that point, the crank would not turn. Same problem I’ve dealt with on other bottom end jobs. Some remaining bearing side-load, I believe, is to be expected. I assume this side-load (in this case) is caused by the flywheel side outer bearing race not yet fully seated (perhaps less than .0005?).
A couple of smart dead-blow pops to the crank end on the clutch side and the crank will now turn, but not freely. It’ll rotate 360 with the same mild drag, but it sure doesn’t turn as freely as I think it should, at least from past experience. At this point, I gave both ends of the crank a number of dead-blow pops with no change in the bearing drag.
What should I do now? I’m afraid of trying to run it in like this for fear of heating up and galling the new bearings. Help, please!

 

[jbighump]

are the seals in? if so they could be causing the drag:msp_confused:

 

[cambl]

I'm not up to speed on Stihls, but I think you may have bound the crank when you used the case bolts to pull the cases together that last 1/4 inch. For the Jonys and Huskys there is a tool that "pulls" the crank into the cases without binding up the bearings or getting the counterwieghts out of parallel.

Do you notice any runout at the clutch end of the crank when you rotate it?

 

[lone wolf]

Is the cylinder on yet can you see if the crank is off center?Keep tapping the ends maybe a brass hammer dont go gorilla on it.Did you forget the center case gasket?

 

[Old Crosscut]

I’ve seen it explained in other posts here, that pulling the cases together using the case bolts is acceptable. I can see where this method would cause minor--final--bearing sideload. I also understand that by pulling the crank/bearing into the case would probably not cause the same problem.
As to my situation, and to questions asked me (thanks, guys), the seals are not yet in or the piston/jug on. Case gasket is in. The crank is centered. I can see equal outer bearing race exposure both sides, inner cases. So any binding/bearing sideload (and it is mild) would logically be caused by incomplete seating (.0005?) between the outer bearing race and the flywheel case side. I’m heating the whole bottom end up on top my wood stove now, and will try a few more crank-end dead blows.
In any regard, the drag is mild. I can turn the crank easily with thumb/fingers on crank. So, the mild drag is probably no big deal. Just doesn’t seem quite right, and it’s bugging me!

 

[lone wolf]

I’ve seen it explained in other posts here, that pulling the cases together using the case bolts is acceptable. I can see where this method would cause minor--final--bearing sideload. I also understand that by pulling the crank/bearing into the case would probably not cause the same problem.
As to my situation, and to questions asked me (thanks, guys), the seals are not yet in or the piston/jug on. Case gasket is in. The crank is centered. I can see equal outer bearing race exposure both sides, inner cases. So any binding/bearing sideload (and it is mild) would logically be caused by incomplete seating (.0005?) between the outer bearing race and the flywheel case side. I’m heating the whole bottom end up on top my wood stove now, and will try a few more crank-end dead blows.
In any regard, the drag is mild. I can turn the crank easily with thumb/fingers on crank. So, the mild drag is probably no big deal. Just doesn’t seem quite right, and it’s bugging me!

Hit it with a brass hammer the bearing aint seated!

 

[lone wolf]

Are they Chinese aftermarket bearings?

 

[Old Crosscut]

Hit it with a brass hammer the bearing aint seated!

Thanks so much, Lone Wolf! You gave me the confidence needed. Bang, bang, and she spins just fine now!

 

[lone wolf]

Thanks so much, Lone Wolf! You gave me the confidence needed. Bang, bang, and she spins just fine now!

Easy for me to say huh ,but the brass wont hurt if you dont go nuts.

 

[acguy]

Bearing cocked

You have a hard bearing cocked in one of the soft magnesium cases. Look at it with magnification, and I'll bet my last dollar one side is cocked. Watch the hammering, you CAN destroy a crank or case. That magnesium fractures like potato chips. Especially if its cold and brittle.

 

[blsnelling]

You have a hard bearing cocked in one of the soft magnesium cases. Look at it with magnification, and I'll bet my last dollar one side is cocked. Watch the hammering, you CAN destroy a crank or case. That magnesium fractures like potato chips. Especially if its cold and brittle.

The way he assembled the saw is perfectly acceptable. Check a couple posts back. He simply didn't have the side load relieved yet.

 

[lone wolf]

You have a hard bearing cocked in one of the soft magnesium cases. Look at it with magnification, and I'll bet my last dollar one side is cocked. Watch the hammering, you CAN destroy a crank or case. That magnesium fractures like potato chips. Especially if its cold and brittle.

Should we ask you how you know?

 

[Old Crosscut]

I’ve gained confidence in my ability as a competent saw repairman--the result of learning so much from all the great folks here at Arboristsite.com. Fix saws now simply as a hobby. It’s very satisfying, certainly gratifying--to hand an old ragged-out beat to death saw back to a friend--clean, running strong, new bar and chain (inevitably, almost always needed). It’s worth the time and effort just to see their eyes light up.
Show me a guy who don’t like chainsaws and I’ll show you a guy who…oh well, mother told me over and over many years ago: Sunny, if you can’t say something kind, then just keep your mouth shut!
So, anyway, thanks again, Lone Wolf, and thanks, Brad--so neat to know you’re always around.
Sure enough, it’s the old dog (I’m 73 now), new trick. Dang, ain’t life great!

 

[PogoInTheWoods]

The way he assembled the saw is perfectly acceptable. Check a couple posts back. He simply didn't have the side load relieved yet.

Most folks would install the bearings in the case halves first. They also wouldn't apply heat to the bearings, but rather heat the case halves and cool the bearings. Crank would go in and halves assembled afterward. A couple whacks with a dead blow or brass hammer to seat everything seems to be common practice for final "seating" (from everything I've read).

Now if I could only remember where I read that and who wrote it...:msp_smile:



Poge