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Author Topic: CB500 k1 Primary shaft bearing spinning in case.  (Read 2118 times)

Offline Kai.chris

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CB500 k1 Primary shaft bearing spinning in case.
« on: September 06, 2025, 11:12:39 AM »
Hoping somebody can help please…
 Should the primary shaft bearing that sits behind the oil pump be able to spin freely in the case? Just rebuilding the bottom end and concerned it’s not right.
In the correct position the bearing can just slide in and out of the casing easily.
Also looks as if the bearing on the other end of the primary shaft has also been spinning in case.
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Offline McCabe-Thiele (Ted)

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #1 on: September 06, 2025, 02:14:38 PM »
That's definitely not right as I'm sure you have realised!
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Honda CB400NA Superdream (current money puddle)
Honda CB500 K1 (second money pit)
https://www.sohc.co.uk/index.php/topic,28541.0.html
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

Offline Bryanj

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #2 on: September 06, 2025, 03:09:51 PM »
No should not spin but not a press fit either, the bearing at clutch side is a slightly looser fit and is trapped by the quarter cicle steel plate held in with 2 bolts
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Offline Murf

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #3 on: September 07, 2025, 10:41:28 AM »
As already said you don’t want the bearings spinning in the housings so maybe use a Loctite bearing retainer when you assemble everything. There is a range of bearing retainer depending on the gap, I am guessing the gap you have will be very small so get the appropriate product. Get  the surface of bearing and housing clean and oil free before use. You will need very little so get a small bottle because it’s quite expensive. Try to get it from a reputable supplier as i believe there is a lot of fake stuff out there.
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Offline Kai.chris

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #4 on: September 07, 2025, 12:02:51 PM »
Thanks for all your replies.

I feel better now knowing Loctite make a product for this very problem.
The gap is very small indeed. Bearing will only slide in by hand once positioned perfectly.

Looks like Loctite 609 (up to 150 deg c) or 620 (232 deg c) will do the trick,, can’t find much info on suitability with oil though.

Will 620 be overkill? Not sure how hot these engines can get.
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Offline Bryanj

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #5 on: September 07, 2025, 03:04:55 PM »
DO NOT loctite the one on the clutch side, it is suposed to be a sliding fit or you can not strip the engine, as i said it is stopped from moving by the retaining plate, part 1 in the pic
« Last Edit: September 07, 2025, 03:08:15 PM by Bryanj »
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Offline Murf

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Re: CB500 k1 Primary shaft bearing spinning in case.
« Reply #6 on: September 07, 2025, 04:13:34 PM »
If the bearing is a pretty reasonable fit, then as far I know you should use one of the thinner viscosity bearing retainers Loctite do.  It’s the sort of thing where stronger or thicker isn’t particularly better.  When the gap is small the thicker fluids are more likely to get pushed off the matting surfaces as the bearing is pushed home. Push the bearing in with a twisting motion then just leave to set as per recommendation.
I would have a look at the Loctite site and on Utube for info.
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