Oh bugger

[peatff]

We used 638 and it stops the spinning, bugger to get back out though if you need to.

[Conner]

I have new bearings on order. Saw runs well just didn’t oil as pump was worn. I would have expected to see more ware in the crankcase and a small ridge. I have plenty bearing fit loctite.

May have to bore the case and fit a sleeve for the bearing if off center.

 

[spudulike]

Check to make sure your loctite type fills gaps well as some are just for retaining and some fill up small cavities. I reckon you will get away with it unless the new bearings are really sloppy in the cases. 

If this doesn't work, you may pick up some second hand cases if you are lucky....ebay does work sometimes.

[Conner]

Il let you know when the new bearings arrive with the new oil seals for the crank. Not too long I hope as il have forgot how it goes back together🤣🤣

[bmp01]

The other thing to take into account is that the bearing gets 'looser' in the housing as the engine warms up (different rate of expansion for steel vs ally, mag). This is part of the reason the bearing is a tight interference fit at room temperature so at running temp you still have some interference. And why heating the case allows easier removal of bearing. 

 

Using a bearing fit loctite (because it is typically installed at room temperature), faces a 'loose fit' challenge at running temperature. It's one of those 'you might get away with it' games.

 

The difference in expansion is tiny, by the way, 0.015mm for 30mm O.D bearing with a 50deg C temp rise. But then the desired interference fit is also a very small amount, circa 0.025 mm  (room temp). Machining tolerances mean that bearings fit is often higher interference than that, 0.05mm.

 

Forget vernier calliper measurements for this level of precision. If the bearing is loose in housing see if you can slide a feeler blade in the gap, that will give you a better idea of where you're at.

 

Sleeving bearing housing is the right fix but it'll cost for a decent job. You can buy shaft sleeves to repair damaged shafts but I've not seen the equivalent for a housing repair. Wonder if you can do a home brew sleeve repair with shim steel ?

 

Fun and games 😆

 

 

 

 

 

[Conner]

I have used shim to repair this type of damage in the past. I have also pop marked cases to tighten up the bearing before loctite. This works well on machinery but haven’t tried it on a crank journal. I have always used internal callipers and a mic to measure accurately just how I was shown many years ago but can’t put my hands on my 25-50 mic.

[openspaceman]

1 hour ago, Conner said:

I have also pop marked cases to tighten up the bearing

In days of old a knurling tool in  lathe on an old piston (car) would pucker up the skirt a bit if it was slappping.

 

In this case has the bearing been rotating in the case? Is the hole in the crankcase oval?

 

Good luck with the repair but I wouldn't like to be the person that buys it after.

Edited September 29, 2021 by openspaceman
added in a lathe for clarification

[Rough Hewn]

I think it’s become a donor saw.

[Deafhead]

Whenever possible I have always popped crankcase halves in the oven before fitting or removing ball or roller races.

[bmp01]

I just looked at video on computer, couldn't see it previously.

"Oh bugger" is about right, you must have 1/4 mm play there. Something is more worn than the vernier numbers you've shown. Which bit is buggered ?

Re shimming, if housing is ovalised to any extent I cant see how you'd shim it without distorting bearing outer race.

 

What saw is it ? Value?