6203 Bearing Chamfers

[L34]

Hi all at AS.Do off the shelf bearings have enough chamfer compared to OEM stihl?
I know you guys use a lot of these (f/w side) on rebuilds.
I thought I read a while ago that some people had locked cranks due to bearings not fitting against the radius correctly.
Thanks in advance,Chris.

 

[alexcagle]

The only saw I've ever ran into that issue was on a Target Quickie saw, which was a Pioneer brand 61 model.
The standard 6202 bearing was close, but was tight after installation because of excessive taper of the standard bearings' chamfer tapers.
If a greenhorn mechanic installed the bearings incorrectly, and didn't relieve the stress, then the bearings will probably fail.
One safeguard I started using on all crank bearing installs is to use something in between the counterweights to guard against accidentally bending the crank.
If you bend the counterweights slightly closer together by whacking the nut to relieve the stress, or even removing a flywheel, it can cause a wobble that tears up the bearings and even the bearing pockets in the crankcase. Outboard clutches are more susceptible to this problem.

 

[Jacob J.]

Centering the crankshaft correctly in the case is the key to making any replacement set of bearings work.

At the dealership, I had to correct a co-worker's repair on a case rebuild because the crank wasn't centered correctly
and wouldn't spin. He used OEM bearings off the shelf but they were mis-aligned.

If you end up cutting a chamfer yourself, be aware of possible stress risers.

 

[L34]

Thanks guys.
I know I have some bearings in my parts box (from a saw) that has more chamfer than a couple of other bearings that I think are off the shelf.
I think they are all 6203??
I you guys use off the shelf bearings on the f/w side i am happy to do also.
You blokes have been doing this longer than me.
Cheers,Chris.

 

[b fish]

Centering the crankshaft correctly in the case is the key to making any replacement set of bearings work.

At the dealership, I had to correct a co-worker's repair on a case rebuild because the crank wasn't centered correctly
and wouldn't spin. He used OEM bearings off the shelf but they were mis-aligned.

If you end up cutting a chamfer yourself, be aware of possible stress risers.

What method do you recommend for centering crankshaft?

 

[Jacob J.]

What method do you recommend for centering crankshaft?

Brass hammer and a good eye.

 

[b fish]

Do you think it’s necessary to support the counterweights to keep crank from tweaking? I thought they would be tough enough that you could center crank or tap off flywheel without. Damage.

 

[67L36Driver]

Not a 61 but a 655BP:
The main bearings are a special.

Not only are they metric OD and width with an inch size bore but the inner ring radius is larger than standard to clear the extra large fillet on the crank cheek.[emoji15]

I have two sets of bearings I bought that don’t fit.

 

[blsnelling]

Do you think it’s necessary to support the counterweights to keep crank from tweaking? I thought they would be tough enough that you could center crank or tap off flywheel without. Damage.

I never used to, but I now like to put a stack of feeler gauges in between the counter weights to make sure nothing bends.