Warming engine case to fit new bearings.

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nickjaxe
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Warming engine case to fit new bearings.

Unread post by nickjaxe » Thu Nov 26, 2015 12:17 am

Fitting new main crank bearing to my B175 Bantam soon...is it normally req to heat the engine case prior to removing the old and fitting the new bearings?

If it is whats the best way to heat...I have gas torches and hot air gun or will a kettle of boiling water do?

Nick.

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Zunspec
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Re: Warming engine case to fit new bearings.

Unread post by Zunspec » Thu Nov 26, 2015 2:24 am

Hi Nick,

Heating the cases and freezing the bearings is the way to go. I would recommend placing the cases in the oven on a low heat to ensure they are heated evenly. Of course you may not be able to get away with that :D . Worked for my 500cc 5TA, bearings practically dropped in.

Cheers Geoff

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Re: Warming engine case to fit new bearings.

Unread post by Willpower » Thu Nov 26, 2015 10:52 am

Agree with Geoff. No more than 100C for 30 minutes and it worked every time when I fitted new mains to various machines.

nickjaxe
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Re: Warming engine case to fit new bearings.

Unread post by nickjaxe » Thu Nov 26, 2015 11:36 pm

Would pooring boiling water over them be a waste of time.

Any need to loctite each bearing in place.

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Zunspec
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Re: Warming engine case to fit new bearings.

Unread post by Zunspec » Fri Nov 27, 2015 2:31 am

Hi Nick,

Boiling water would not be a complete waste of time but it would take a bunch of it to heat the cases up sufficiently. The oven method is much better, do one side of the cases at a time, there is really not a lot of fuss if the cases have been WELL degreased/cleaned before hand.

Cheers Geoff

nickjaxe
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Re: Warming engine case to fit new bearings.

Unread post by nickjaxe » Sat Nov 28, 2015 1:02 pm

And no chance of distorting the case...I am a born worrier.

Triton Thrasher
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Re: Warming engine case to fit new bearings.

Unread post by Triton Thrasher » Mon Nov 30, 2015 2:59 pm

No point in Loctiting.

Willpower
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Re: Warming engine case to fit new bearings.

Unread post by Willpower » Mon Nov 30, 2015 4:50 pm

Case will not distort at low temperatures in the oven as it's are warming up uniformly and usually the bearing just drops out of the case when its ready.
Agree with TT that not loctite, etc is needed for refitting.
Have the new bearing ready, it should drop straight in as soon as the old one drops out (maybe a little tap with a plastic/wooden mallet). Saves warming the case again.

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Hooli
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Re: Warming engine case to fit new bearings.

Unread post by Hooli » Mon Nov 30, 2015 6:54 pm

Put the new bearing in the freezer a few hours before, makes sure it just slips in while the cases are hot.
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Bobber-job
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Re: Warming engine case to fit new bearings.

Unread post by Bobber-job » Mon Jan 11, 2016 5:05 pm

Have done the oven method with all my 2 strokes and it works a treat esp chilling the bearings as well - one problem I did find was when the cases cool they can sometimes push the bearings back out of the case by a few thou. make sure you gently tap the outer race to ensure they are properly seated. on a Bultaco it was enough to stop the crank turning when the cases were torqued up.

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