Main bearing installation

[SirFallsALot243]

I was watching a video of a guy rebuilding his bottom end today, and to press his bearings in he used a heat gun. He heated the case, causing it to expand, and the bearing dropped right in. I was wondering- is this ok to do, or will it weaken the case?

[Spitfire]

From what I understand, it should be fine to heat the cases, as long as there is no direct flame going onto the cases. When I did my main bearings, we heated up the cases in an oven, and the bearings dropped right in.

[Faded]

Make it even easier and throw the bearings in the freezer for a while.

[SirFallsALot243]

Thats what i was thinking faded. Thanks guys.

[ossagp]

propane torches or heat guns,,hair dryers,,ovens they all work. dont know where the no direct flame tale started. moderation in everything.

the freezer or just outside here in winter works wonders.

heat the cases to remove the bearings too,,they practically fall out sometimes.

on reassembly, get them into the case, use a heated slug on the center of the bearing,,and insert the crankshaft. i make shims out of business cards to center the crank, no tapping necessary afterwards etc. just measure across the crank,,then measure the crank cavity,,split the difference and shim.

[boogieonmyfinger]

2 questions -

1. If they don't fall out, how do you get them out?

2. Can you explain the shim thing in more detail? Are you shimming it to center it in the cases?

thanks

[SirFallsALot243]

If they dont fall out you hit them out with a punch and a hammer I think.

[boogieonmyfinger]

Sounds good. I was thinking the bearings were set into the cases with no access to the back side of it.


Nice banana.

[99kx250rules]

I watched the Kawi tech change out the crank and bearings on my bike. Using a torch is fine when done right.

[ossagp]

you push the bearing out from the outside in,,if that makes sense. if not, once you have the cases apart you will know what I mean. one way that usually works and just requires a set of oven mitts is to warm it, take it in your mitted hands and smack it open side down on a phone book or similar. A punch or a large wooden dowl works if you want to drive them out.

yes on the shimming,,you just are looking for something to center it with. if you do that and warm the bearing centers enough to get a good "hand pressed" fit you alleviate some bind. lay the base gasket on and see that you will likewise be centered in the bore (don't laugh, i had a yamaha that was way off there, the crank had to be nearly an eighth inch to the primary side to get the rod in the center). it also allows you to take those business cards handed to you by insurance and realestate sales people to go to good use.

[Mainjet2001]

Andy.....you are something.
I love reading your posts because there is always a little gem in there.

I now know what to use that business card I have from that IRS agent. It really is good for something.....

[Aus_Rider_22]

Nice thread!

PLenty of info! You learn something new every day!

[RICHIE500]

Yeah good info guys!!