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Crankshaft End Float (can it be measured?)

Submitted by leslie,peter_howard on Thu, 15/07/2010
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Heavy Twins

I have in the past rebuilt many motorcycle engines including Dominator motors, but not recently.

As I will soon have to rebuild an early engine, I have this question.

As most of you will know, the Dominator engine has a roller bearing on the drive side and a ball bearing on the timing side.

As both bearings should be a tightish fit on the crank mainshafts, sometimes secured with Loctite, how on earth can the âEnd Floatâ be measured?

I can see how shims can be added behind the roller bearing inner race to centralise the crankshaft within the case but as far as end floatâ?.surely that is impossible as the timing side ball bearing will hold the crankshaft rigidly as far as in line movement is concerned?

To replace the timing side case half, the best way is to heat the inner race with a heated mandrill so it can expand and slip over the timing side shaft, but once cooled, it will hold the shaft firmly and not allow anymovement, (apart from the tolerance of the bearing itself) so I would appreciate your views and explanations please. Manuals always quote a measurement for this.

âTis a mystery to me.

Many thanks.

Regards.

Les

Submitted by leslie,peter_howard on Thu, 15/07/2010

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For Clarity of answers, please answer on the "Quick Reply " box at the bottom as this prevents all those silly red lines and repeated messages fromappearing and thus making for an easier read of the message string...Many thanks again...Les

Submitted by warren_dagnall on Thu, 15/07/2010

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Hi Les.

If things were as you describe it would indeed be impossible to check. BUT the Ball inner is only a light fit to the shaft and movement is found there. Surely you will be going to a twin roller set up any way ( Superblend )? and you can play to your hearts content.

Ron C.

Submitted by leslie,peter_howard on Thu, 15/07/2010

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Hi Ron.

As far as I can remember the bearing should be quite a tight fit. In my experience a slack fit results in the mainshafts spinning inside the inner bearing and wearing away the shaft. I had this happen to a 99 and had to have the main shaft metal sprayed to build it upand make the bearinga good tight fit with no spin. Nowadays Loctite can be used.

I think I can remember recently reading thata high capacity BALL bearing is sometimes now preferredon the Commandoengine just for the very reason to avoid shimming worries.

Surely, If the timing side bearing was solidly locked onto the timing side shaft there would be no problems as long as the engine was assembled cold. When the crankcases heated and expanded, all that would occur is the roller on the drive side would be moved slightly out of its cold running track position but return when cold.

I don't think a Superblend bearing will have any advantages in a Model 7engine as it is so lowly stressed.

Coming back to measuring the end float, I would imagine that the fit of the bearing on the timing side would have to be VERY loose for one to be able to actualy move the crankshaft back and forward for measurement...so loose in fact it would surely spin as I have said.

Your viewsmost welcome again Ron.

Thanks

Les H

Submitted by warren_dagnall on Thu, 15/07/2010

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Hi Les The superblend thing was a bit tongue in cheek remark, I fitted them, simply because if you are fitting new why not, personnel preference.

End float, well thatâs the way itâs done, the inner race is pinched between the crank and the oil pump worm when itâs all tightened up.

Ron C.

Submitted by leslie,peter_howard on Thu, 15/07/2010

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Hi Ron.

Excellent, you have explained it. So one should expect a sliding fit on the timing side bearing, thus enabling the end float to be measured, and then the oil pump worm, when fully tight binds the inner of thebearing solidly to the crankshaft end. Yep that makes sense, so I'll keep off the Loctite on the timing side, but the drive side is better Loctited into the case and onto the shaft to prevent any movement at all.

Thanks Ron...after all these years!

Much obliged.

Les H

Submitted by warren_dagnall on Thu, 15/07/2010

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Hi Les, The interference fit of the inner ball race should be a light drive fit. Checking end float is not a nice engineering job as some force is required.

Go easy on the Loctite, think about the poor guy that has to get the thing apart next time!

Regards Ron.

Submitted by paul_wilson on Thu, 15/07/2010

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Leslie Howard wrote (on 15th July 2010. 18.24hrs):

>Oh dear...shame this string has got it's running order all out of line.

When will they sort it out?

Les<

Hello Les,

I attempted to raise the same question on the Message order reversal thread (Website Suggestions) on June 19th.

It began: 'Hello Peter'

Although I made a mess of the formatting, I think the gist of myquestion was easy enough to understand; but there was no response.

Paul

 


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