New bearing ruining from a propane torch?

[slambox28]

HI, is it possible to ruin new crank bearings with a propane torch? Holding the flame at a distance and all of a sudden see the oil coating poof into a flash of flame, installed and nothing added. Never became discolored or purposely try to heat it too fast. The crank is centered but wondering if the bearings can be ruined from a small regular bottle tank propane torch from Walmart. There seems to be high resistance but also might be the install that changes the size of the race just slightly.

 

[Bob Hedgecutter]

It certainly can if the bearings were plastic caged ones.
I fail to see why the bearing required heat from a propane torch anyhow? Ideally you heat the bearing pocket in the case and drop the bearing in, sometimes you might even put the bearing in a freezer for a while first.
The idea is to use heat to expand the size of the bearing pocket and cold to shrink the bearing so they slip fit.

Or were you heating the bearing to slip it onto the crank, then pull the lot into the cases?

 

[slambox28]

It certainly can if the bearings were plastic caged ones.
I fail to see why the bearing required heat from a propane torch anyhow? Ideally you heat the bearing pocket in the case and drop the bearing in, sometimes you might even put the bearing in a freezer for a while first.
The idea is to use heat to expand the size of the bearing pocket and cold to shrink the bearing so they slip fit.

Or were you heating the bearing to slip it onto the crank, then pull the lot into the cases?

Yessir, I was heating to put both on the crank, the race is fully metallic. The torch was moved around quickly and kept at a distance, while focused on the inner race. It's just a camping torch propane n/a. The second bearing I heated, the factory oil coating flashed away in a split second, just a quick small flash. But I noticed more resistance on that side which is the reason for asking. The crank was just air temp around 70deg F. Maybe the resistance is normal for after installing it? But no lubricant was added to it either, could this cause too much resistance to a saw to run?

 

[Bob Hedgecutter]

I wouldnt think so- but then I wasnt there to watch you put them on the crank.
Im still picking side loading on the bearings is your issue.
After installing the bearings and crank in the case halves and screwing them up- you will have pulled side load onto the bearings- it can be corrected by hitting the crank stubs with a SOFT faced hammer.

This is assuming the correct size, correct spec bearings were used from a known bearing company and not cheapest you could find on Amazon.

 

[slambox28]

I wouldnt think so- but then I wasnt there to watch you put them on the crank.
Im still picking side loading on the bearings is your issue.
After installing the bearings and crank in the case halves and screwing them up- you will have pulled side load onto the bearings- it can be corrected by hitting the crank stubs with a SOFT faced hammer.

This is assuming the correct size, correct spec bearings were used from a known bearing company and not cheapest you could find on Amazon.

SKF bearings from wolf creek saw shop; commonly used for builds, USA made. And the backside of a hatchet from tractor supply co. The bearing slipped right on, the resistance was noticed after heating and sliding on the crank but before putting the crank into the case. The oil did burn off for sure it flashed away in a split second for the 2nd heated bearing.

 

[Bob Hedgecutter]

So you noticed rotational resistance before the crank was reinstalled in the cases- but installed them anyhow and the resistance is still there?
I would suggest something went wrong during installation and that side bearing is misaligned within itself.
The back end of a hatchet is possibly the cause- perhaps the cage that holds the individual balls of the bearing at the set distance apart is now bent.
Continuing the build with this issue is likely to lead to premature bearing failure- so it sounds like you are going to need to start over- I would suggest buying an electric fan heat gun and watching the likes of this video- to show how the crank should freely rotate after installation.

 

[slambox28]

So you noticed rotational resistance before the crank was reinstalled in the cases- but installed them anyhow and the resistance is still there?
I would suggest something went wrong during installation and that side bearing is misaligned within itself.
The back end of a hatchet is possibly the cause- perhaps the cage that holds the individual balls of the bearing at the set distance apart is now bent.
Continuing the build with this issue is likely to lead to premature bearing failure- so it sounds like you are going to need to start over- I would suggest buying an electric fan heat gun and watching the likes of this video- to show how the crank should freely rotate after installation.

That's the exact video I watched how to do it with!

The 2nd bearing just slipped right on but (when heating) flash burned away the factory oil coating. No hammering at all on it just slipped on. The first bearing didn't get as hot and got stuck 1/2 way again no hammering. The shaft is all the same diameter by design but the 2nd was sluggish on the spin like it had slight resistance. Noticeably more than the first...

The 2nd one never got hammered either just heated and seated by using the case and tapping the end of the crankshaft...

The saw won't start and it seems like it might have more resistance than it should from the bearings... And I noticed the 2nd bearing sluggish to spin and stopping noticeably quicker than the first... So just not sure if the propane torch might've ruined a new bearing.

Really don't know what went wrong with the saw... Gonna help diagnose with a new crankcase and engine assembly and need to do some cutting with a 42" bar on elm

 

[Bob Hedgecutter]

You are going to bolt a 42 inch bar onto a 372 and expect great results?
I guess you have to sort it out and get it running first- but still- a 42 is going in a bit over barred and under gunned.

 

[slambox28]

You are going to bolt a 42 inch bar onto a 372 and expect great results?
I guess you have to sort it out and get it running first- but still- a 42 is going in a bit over barred and under gunned.

Really a 76cc saw? Running a 42" bar? it runs like a banshee and insanely powerful... Idk probably gonna find out

 

[slambox28]

Just going to cut firewood out of 5' diameter elm... Think it's going to be fine but we'll see... 65 cc watercooled will put the front wheel off the ground with a 180lb man (2006 rm65)