C15Main bearing installation on crank

[rhyatt]

good morning,
I have just received my renovated crank back and I am offering the new 6305 drive side ball race up to the crank.
bearing in mind potential in/out for end float shimming, should/must ? the crank shaft just glide smoothly and squarely into the inner race?
as opposed to any form of mild force - I can heat the crankcase to drop the bearing into it no problem , but need to ensure that I can get the crank in/out of the bearing to facilitate any shimming required.
thank you.
the standard ID for the bearing is (i believe ) 25mm , so I may need to "polish" the crank a shade I wonder?
as best as I can , my crank is 25.02/03

[limeyrob]

The parts book shows shims but its not clear that there were ever used or fitted.  You may not need to pull the bearing off.

[rhyatt]

yes thank you - seen the shims - but at this moment, I cant get the 6305 onto the crank(or the crank into it) to enable me to establish whether I actually need shims or not.
common sense tells me that the crank should smoothly glide into/ and out of the ID of the ball bearing.
once the need for shims or not is established , the crank can all be built up on the drive side in situ and hopefully never see daylight again !!

[Stubaker58]

Hi Richard,

This is the issue with the cranks! The bearing should be (very) tight on the shaft, the shaft should not slide freely.

Measuring "end float" is difficult (at least I found it difficult) I used the old bearing .. I opened out the inner race so it was a sliding fit, put the bearing in the case, bolted everything together and measured the "end float.

I then took the bearing out, put the new, tight, bearing (same dimensions as the old) in added shims to give 4 thou gap and bolted it all together. I have a crank puller to pull the crank through the bearing (it can also push the crank out of the bearing).

A cleverer person than me would be able to measure the gap very accurately without all that faff but my instruments (and my brain) couldn't cope!

You're welcome to borrow my crank puller if you like to.
Regards.

[rhyatt]

Ah , tight on the crank is the answer.
I even thought about creating a dummy bearing type thing same Id and od as the 6305 to slide in the crankcase and also accept the crank to facilitate the shimming measurement process.
Thank you for the offer of your tool.

[limeyrob]

I think relieving the old bearing is the best method.  The new bearings can be a tight fit and they can get damaged when you take them off to fit the shims, especially if they have a plastic cage.  If the bearing is too loose a fit it can spin and destroy the shims which then land in the sump so the tight fit is good but you just don't want to be sliding the tight bearing on and off too many times.

[rhyatt]

I am trying to look calmly at the reassembly process of my crank into the crankcases - looking at service sheet 424 it seems so simple!!! "just place this on that" .

warming the 6305 bearing to place it on the crankshaft and then warming the crankcase to get that lot into the drive side crankcase - there has to be a simpler method !!

Thank you Stubaker for your offer of the puller to draw things together. I will PM you.

how do others do this job - I am all ears !!

[Mark Cook]

For any crank in a vertical split engine.
Measure the width of the crank.
Measure the space in the crankcase.
Calculation is the quick and easy answer.

Mark

[rhyatt]

Mark,
Thank you for this idea, but this crank has various shoulders etc on it which don't make calculation easy and the running width is not at all easy to ascertain.
Thank you anyway

[limeyrob]

If you haven't already done so drill a hole for the crank in your bench or in a large bit of wood so you can lay the case flat then drop the crank in.

[rhyatt]

Thank you , i have a good assortment of wood blocks thank you

[Tigerfeet]

Do you need one of these?  https://www.ebay.co.uk/itm/265809397131

[rhyatt]

thank you - but I borrowed an identical tool.

however - whilst warming the cases to drop the drive side main bearing in, i used my hot air gun and warmed it round the area, lowered the bearing into place expecting to tap it home --but it literally dropped into place - then --
whilst sorting out wood etc, the heat transferred into the bearing itself and caused it to expand and the crank literally dropped home snugly.

thank you anyway for your thoughts