036 crankshaft alignment/bad trade

[AgTech4020]

I recently traded a nice MS250 for a non running but complete 036 Pro. The saw had lots of compression and new (aftermarket) plastic but had a good STIHL 20” bar and chain. Upon getting home I found the impulse line bad. I installed a new impulse line and the saw started and stayed running on the third pull. It had real snappy throttle response and idled smoothly laying on all sides. I sharpened the chain and cut with it for about three tanks of fuel. It ran good but didn’t lug like my MS360. I brought it back to the shop and did a compression check the next day, 175 psi in two pulls cold. I looked at the cylinder through the plug hole and was shocked at how badly the cylinder was scored. I could see where it was gouged through the plating in several spots. I removed the cylinder to find it was badly scored all the way around. I have no idea how it could make 175 psi compression. The cylinder is a very obvious low end aftermarket. A closer inspection led me to find that the crankshaft is offset towards the pto side. The crank is shifted far enough that the counterbalance has been rubbing the paint off the crankcase.

Has anyone successfully tapped a crank back to center without damaging the crank? I’ve got a new Hyway cylinder I could polish the ports and throw on it but the crank has me nervous. Both bearings appear to be metal caged and look fine. I do suspect the crank is also aftermarket but is tight and looks fine.

Thoughts?

 

[AgTech4020]

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[rupedoggy]

Yea dead blow hammer and center that thing

 

[pioneerguy600]

The cranks almost always need centering after case assembly so yes go ahead and give it a couple good taps, brass hammer, lead ,aluminum or dead blow just so the crank end is not damaged.

 

[Deleted member 135597]

Measure the gap and divide by two. Place a feeler gauge the thickness of the number you came up with against the flywheel side in your case and whack it till it touches. This way it’s perfectly centered.

 

[Chainsaw Jim]

It's offset to the pto side because the bearing on that side is set too deep. When set correctly the crank weights won't be able to touch the case.

 

[tomdcoker]

Yea dead blow hammer and center that thing

I put the nut on the crank and run it down until it is flush with the end of the crank. Tom

 

[AgTech4020]

I have put together several crankcases but I always measure first and then use feeler gauges to make sure the crank ends up in the correct spot on the first try. I have never tried tapping one around other than when first installed and there is still a good temperature differential between components. I will give it a try and hopefully it stays where it supposed to.


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[AgTech4020]

It's offset to the pto side because the bearing on that side is set too deep. When set correctly the crank weights won't be able to touch the case.

In that case should I completely disassemble and reassemble with the bearing in the right spot or do you think just tapping it over will work?


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[BangBang77]

The industrial mechanics and millwrights that work for me would be fired on the spot for hammering on a bearing or shaft.

Delta T, or temperature differential, is the only "correct" way to install a fit bearing, albeit a press is occasionally needed depending on size of components. Poor installation is the #1 cause of pre-mature machine failure. #2 is out of spec machining/fabricating causing tolerance stacking, and #3 is excessive or inadequate lubrication.

But we build and service multi-million dollar production machinery and I have a healthy dose of OCD about doing everything right the first time.

I'd split the case if it were me...

 

[Chainsaw Jim]

In that case should I completely disassemble and reassemble with the bearing in the right spot or do you think just tapping it over will work?


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I'd be careful trying to tap the bearing over because there isn't as much thickness on the outer edge. It might be a great excuse to split the case to install new bearings if it's in your budget. The "6202 c3" flywheel side bearing can be purchased at just about any bearing supply store for around 5 bucks.

 

[huskihl]

The industrial mechanics and millwrights that work for me would be fired on the spot for hammering on a bearing or shaft.

Delta T, or temperature differential, is the only "correct" way to install a fit bearing, albeit a press is occasionally needed depending on size of components. Poor installation is the #1 cause of pre-mature machine failure. #2 is out of spec machining/fabricating causing tolerance stacking, and #3 is excessive or inadequate lubrication.

But we build and service multi-million dollar production machinery and I have a healthy dose of OCD about doing everything right the first time.

I'd split the case if it were me...

You still need to tap the crank back and forth after assembly to free the bearings up.
Delta "T" is pretty much non-existent at that point

 

[BangBang77]

You still need to tap the crank back and forth after assembly to free the bearings up.
Delta "T" is pretty much non-existent at that point

I agree that some "tapping" could be necessary.

 

[huskihl]

I agree that some "tapping" could be necessary.

So you're saying that there should still be enough heat differential for the bearings to center themselves?

 

[BangBang77]

So you're saying that there should still be enough heat differential for the bearings to center themselves?

I don't believe that is what I said; I just didn't comment on that portion of your post.

But since you asked so nicely...no. There will probably not be enough Delta T to center the bearings.

 

[huskihl]

I don't believe that is what I said; I just didn't comment on that portion of your post.

But since you asked so nicely...no. There will probably not be enough Delta T to center the bearings.

Sorry you interpreted my question as being asked nicely. Lol. I was curious if there was a way to heat bearings and cases enough as to not require relieving side load inherent with this type of assembly.

 

[blsnelling]

Center the crank and move on.

 

[BangBang77]

Sorry you interpreted my question as being asked nicely. Lol. I was curious if there was a way to heat bearings and cases enough as to not require relieving side load inherent with this type of assembly.

The only way I have found to do that are to submerse the crankshaft assembly in dry ice, install the crankcase bearings in the crankcase halves, prep the crankcase gasket/sealant, and slide the crankshaft into both halves.

I have only been into 2 saws this deep in my life - an 026 family heirloom and an 026 Pro that I picked up from my local dealer that had a smoked top end. I used the same heat/cool principles as I always have on machinery and it has worked for me twice. I am not sure how others do it as I don't typically ask for help on how to disassemble/assemble much of anything. I may be doing it all wrong...

 

[huskihl]

The only way I have found to do that are to submerse the crankshaft assembly in dry ice, install the crankcase bearings in the crankcase halves, prep the crankcase gasket/sealant, and slide the crankshaft into both halves.

I have only been into 2 saws this deep in my life - an 026 family heirloom and an 026 Pro that I picked up from my local dealer that had a smoked top end. I used the same heat/cool principles as I always have on machinery and it has worked for me twice. I am not sure how others do it as I don't typically ask for help on how to disassemble/assemble much of anything. I may be doing it all wrong...

They will go together with ice and heat. Usually before the screws are snug, the temp differential has decreased enough to where things tighten up, creating a slight side load. I would guess that after a few heat cycles things may loosen up on their own, but a few taps on either end of the crank with a soft hammer will release the side load to where the crank can spin freely before running the saw. Some say this will prolong bearing life. I guess it all depends on if or how long the bearings take to center themselves

 

[pioneerguy600]

Just think, we have been doing this all the wrong way for so many years. I must tell my saws about this.