036 PRO crank re-assembly

[TTuke]

Hey folks,

So, I recently got all the parts I ordered for the rebuild of an 036 PRO I purchased. When I acquired the saw, it was locked up, the piston had crumbled from the intake side and took the cylinder with it. I figured it would be a good culprit for the first saw that I'll fully rebuild. I do have a pretty good mechanical understanding of things, and everything in the bottom end seemed okay upon inspection, though I did not throw a dial indicator on the crank to check for a bent crank.

I bought new crank bearings and seals, top end, and gasket set. All OEM, except the crank bearings as my local STIHL dealer told me they have been discontinued. I ended up getting CROSS bearings. When I went to reassemble everything went smoothly, until I tightened up the case bolts and the crank was very hard to roll over. Borderline unable to turn it by hand.

I don't currently have a dial indicator at home so I can't confirm, but I am fairly confident the crank is bent. Upon disassembly and cleaning (A real nightmare!! The guy ran veggie oil) I noticed some other tell tale signs that I should have payed more attention to on the coil and flywheel, as photographed. I was just hoping someone might be able to chime in and give me their two cents before I buy a crank for this saw (that I'm currently wishing I just used for parts hahaha)

 

[mike-s]

everything went smoothly, until I tightened up the case bolts and the crank was very hard to roll over. Borderline unable to turn it by hand.

Guessing you simply pulled the case/bearing onto the crank using those bolts. That results in a lot of bearing side-load. Best way to fix is pull the seals and use a pipe or socket which fits over the crank and onto the inner bearing races, and press them onto the crank a bit more (or give a few light taps to push the races on further). You can also simply tap the crank with a plastic hammer (or use a block of wood to protect the end threads), without pulling the seals. That's a bit harder on the bearings, though.

 

[pioneerguy600]

Side load on the bearings is the most likely culprit. A couple raps on the crank ends with a lead hammer, other soft faced hammer will help unload the bearings and make the crank easier to rotate.

 

[lone wolf]

You will know if the crank is bent when you soin it over with the coil on and see if its out of true by the clearance as it rotates..

 

[pioneerguy600]

You will know if the crank is bent when you soin it over with the coil on and see if its out of true by the clearance as it rotates..

Turn it over?

 

[Mad Professor]

Your Stihl dealer is a liar, and/or probably wanted to sell you a new saw.......

036 crank bearings

9503 003 0346 BALL BEARING $15.81

9523 003 4266 BALL BEARING $17.65

What @pioneerguy600 said ^ about bearing preload/centering crankshaft.

Coil/flywheel issue is most likely no clearance, should be ~0.010" that's a guess, can't remember exact

 

[lone wolf]

Turn it over?

Roll it over by hand after he frees it !

 

[pioneerguy600]

Roll it over by hand after he frees it !

Thought you meant that but the word or spelling you used left some confusion.

 

[TTuke]

Thanks everyone for the responses! I'll give it another go.

So, by the sounds of it, the likeliness is pretty low that the crank is bent?

 

[pioneerguy600]

It takes a lot of pressure to bend a crank, doesn`t happen often just pulling cases together.

 

[cuinrearview]

Your Stihl dealer is a liar, and/or probably wanted to sell you a new saw.......

036 crank bearings

9503 003 0346 BALL BEARING $15.81

9523 003 4266 BALL BEARING $17.65

What @pioneerguy600 said ^ about bearing preload/centering crankshaft.

Coil/flywheel issue is most likely no clearance, should be ~0.010" that's a guess, can't remember exact

That made me lol too. That's a dealer I'd never be visiting again...

 

[TTuke]

Well that’s unfortunate to hear about the bearings! Hahaha

My only thought with the crank possibly being bent, was that maybe it happened when the piston failed. If it locked up immediately would that possibly bend the crank? Or is that pretty unlikely, and perhaps it would bend the connecting rod first

 

[pioneerguy600]

They can be bent, only a test will tell. If the gap between the flywheel and the coil changes a good bit when the flywheel is rotated then there is a possibility the crank bent. I had a saw in that the flywheel would hit the coil at one point and have 250 thou clearance on the opposite side.

 

[TTuke]

Yikes! That’s aggressive.

Okay, thanks folks! I’ll do some more work tomorrow and see what I come up with

 

[lone wolf]

Thought you meant that but the word or spelling you used left some confusion.

Yup. You are right.

 

[L34]

Put a wood wedge between the counter weights when installing crank to stop bending/loading also.

 

[drf255]

Wack the crank back and forth like Jerry said, but use a punch in the crank center. There is a recess in both sides for a punch. I’ve seen a few damaged cranks, even using a brass hammer. You‘re probably just side loaded, as stated above.

I have never seen a bent crank in an 034/036. Be careful to clean and inspect the large rod end and bearing on the crank. Make sure there isn’t any play. I HAVE had debris in the large end of a saw that grenaded let out continual debris and keep scoring an engine. Went through 3 pistons till I figured it out. Make sure u washed it out thoroughly.

The flywheel hit is probably from bad bearings letting the crankshaft move too much, or loose coil bolts.

 

[rupedoggy]

Look at your crankcase from above (with crankshaft installed). Notice how it is more to one side than the other. Smack it to the center..... voila!