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Starter motor bushings

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Starter motor bushings

Posted by luke_albanese at June 14. 2011

Does anyone know the bearing dimensions (and part references) for the oilite bushings in the Prestolite starter motor.

 

I know the drive end dims, but I'd like to find out about the cap (brush) end bearing.

 

Thanks,

 

Luke Albanese

Re: Starter motor bushings

Posted by luke_albanese at June 14. 2011

Turned out to be 3/8" i.d., 1/2 " o.d. and 3/4 " long.  Oilite AA-521

Re: Starter motor bushings

Posted by tim_gostling at June 15. 2011

I've replaced the oilite bushes with needle roller bearings in my motor & the difference is amazing, it's still standard 2 brush with a mini type solenoid, better leads & a 12 a/h battery (yes, 12 amp hour, smaller than standard) & it spins the engine with ease form cold !  I think the inherant drag in oilite bushes steals too much of the motors power & there's not enough left to spin the engine.  Try spinning your motor by hand (off the bike, of course) & you'll find that it won't, when you stop turning it, it'll stop ! with the needle rollers mine now spins freely. The bearings I used required no modification of the armature but did require the end covers reaming out to take the larger outer diameter. Well worth the effort.

 Regards, Tim

Re: Starter motor bushings

Posted by jack_blakemore at June 15. 2011

Tim - do you have the specification of the bearings please?

 

Re: Starter motor bushings

Posted by tim_gostling at June 15. 2011

Previously wrote:

Tim - do you have the specification of the bearings please?

 

To the best of my memory & oily fingerprint stained notes, the drive end was a B118, which should be a Drawn cup needle roller bearing, 11/16" ID, 7/8" OD & 1/2" width & the brush end was a B610, which should also be a Drawn cup needle roller bearing, 3/8" ID, 9/16" OD & 5/8" width. If your armature shaft is worn, I believe an inner race is available for both, you would obviously need your armature machined for these to fit. The bearings were not very expensive, arround £10 I think. Another obervation I made was when reassembling, I held the starter body gently in a vice & while tightening the 2 long studs kept turning the armature & 'shuffling' the two end covers, it was supprising how much more freely the armature spun when it all settled correctly. Also remember to shim the end float correctly so the brushes run roughly centrally on the commutator. If you need any more help or info or cant find the bearings please feel free to ask & I'll do my best to help.

  Regards, Tim

Re: Starter motor bushings

Posted by luke_albanese at June 16. 2011

Previously wrote:

Previously wrote:

Tim - do you have the specification of the bearings please?

 

To the best of my memory & oily fingerprint stained notes, the drive end was a B118, which should be a Drawn cup needle roller bearing, 11/16" ID, 7/8" OD & 1/2" width & the brush end was a B610, which should also be a Drawn cup needle roller bearing, 3/8" ID, 9/16" OD & 5/8" width. If your armature shaft is worn, I believe an inner race is available for both, you would obviously need your armature machined for these to fit. The bearings were not very expensive, arround £10 I think. Another obervation I made was when reassembling, I held the starter body gently in a vice & while tightening the 2 long studs kept turning the armature & 'shuffling' the two end covers, it was supprising how much more freely the armature spun when it all settled correctly. Also remember to shim the end float correctly so the brushes run roughly centrally on the commutator. If you need any more help or info or cant find the bearings please feel free to ask & I'll do my best to help.

  Regards, Tim

Tim,

 

This is fantastic, many thanks.  Can I just ask you what you shimmed the end float with?  Did you use bronze thrust washers or just normal steel washers or something else?

 

Kind regards

 

Luke

Re: Starter motor bushings

Posted by luke_albanese at June 16. 2011

Tim,

BTW - can you advise on how to ream the caps?  I suspect the B118 will drive straight in, but I'm sure the B610 will need reaming.  Not having a lathe or milling machine I'm wondering the best way to achieve this?  Could I just use a 9/16 drill, handled slowly?

Kind regards

 

Luke

Re: Starter motor bushings

Posted by tim_gostling at June 17. 2011

Previously wrote:

Tim,

BTW - can you advise on how to ream the caps?  I suspect the B118 will drive straight in, but I'm sure the B610 will need reaming.  Not having a lathe or milling machine I'm wondering the best way to achieve this?  Could I just use a 9/16 drill, handled slowly?

Kind regards

 

Luke

Luke,

 To shim the end float I used hard steel shim washers, these are readily available in various dimentions & thickness, just grab a selection & you should be able to get it right without too much trouble, remember to leave a little float so things don't tighten up when it all gets hot. 

  As for the reaming, both ends need approx 1'16" tacking out, the drive end is easy, I used an expandable reamer & just took a little at a time untill I had the correct 7/8" bore to take the B118. The brush end is slightly more difficult as we are dealing with a blind hole. For this I set the cover up in a drill vice (I made up a pair of wooden blocks with a semi circle cut out which held the outer diameter of the cover so it was supported securely) & used a pillar drill, I started with a slightly under sized drill & finished with a 9/16" reamer, you don't have to go right to the bottom as the bearing is slightly shorter than the original bush. If you do go a bit too far with either end & have a loose fit, you can always fit the bearing with a spot of Locktight bearing fit, magic stuff made for rescuing worn bearing housings. Hope this helps, please ask if you need anything further.

  Regards, Tim

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