Author Topic: Warning to 500K0 owners--dodgy mainshaft needle roller bearing  (Read 1933 times)

Offline AshimotoK0

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Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« on: September 19, 2018, 02:45:18 PM »
When I  stripped my 3/71 500K0 engine, the bottom end was in very good shape except that the cage in the main-shaft needle roller bearing was cracked in a couple of places.
I thought I may be lucky in that the mainshaft bearing surface appeared to good and not scored or discoloured. However, getting my 'ducks in a row' ready to rebuild the engine I investigated further and looked at the bearing surface under a 15x magnifier today  and there is weird micro crazing all over the surface. Luckily, Bryan on here let me have a spare shaft and studying that one, it doesn't show any signs of the crazing effect like there is on my original. The needle roller bearing is unusual in that it has needles in individual pairs, separated by the cages  and is different from the counter-shaft one, which has needles equi spaced and is a CB250/350K  ---286--- part. The mainshaft one is P/N 23931-323-004, so obviously a part first used in the CB500/4

I gather from 500 gurus on this forum that there were early gearbox failures on 500K0, which Honda tried to cover up and it partly related to there being a Class Action law case against them in the USA in 1971. It would kind of explain why we never officially got the K0 model here. Trigger once showed me 550 version, where there is a little trochoidal oil pump built into the bearing assembly ( I think Oddjob had told me about that mod too).

So if you have a early 500 and have the bottom end apart it would be prudent to check out that bearing and the mainshaft it runs on.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Trigger

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #1 on: September 19, 2018, 03:41:27 PM »
I have built a few early CB500 engines and 9 out of ten have had problems that you have mentioned Ash. Even my own early  UK, K0 had a locked gear box and i had to replace the shaft and needle bearing.

Offline deltarider

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #2 on: September 19, 2018, 04:04:31 PM »
Quote
The mainshaft one is P/N 23931-323-004, so obviously a part first used in the CB500/4
I doubt the needle bearing itself is the problem because that part is still in the CB500s that were assembled in 1975-6, like the CB500K2 (ED, F, G), be it that there were some changes. For these changes see pages 26-9 in: http://www.honda4fun.com/pdf_parts_list/pdf_spac500/CB500-76/CB500-76_2.pdf

Offline AshimotoK0

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #3 on: September 19, 2018, 04:07:11 PM »
I managed to get a shot of the surface on my digital microscope to show what I found on the shaft. The cage on the needle roller that I got with the replacement shaft is steel but from memory it was some form of alloy on the original. I will try to find the old one to confirm. I reckon Toyo changed the internal construction of the bearing but Honda still gave the new part the same P/N.

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« Last Edit: September 19, 2018, 04:11:13 PM by AshimotoK0 »
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Trigger

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #4 on: September 19, 2018, 04:07:29 PM »
Not the first part used with a number ending in 004  ;)

Offline AshimotoK0

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #5 on: September 19, 2018, 04:13:50 PM »
Not the first part used with a number ending in 004  ;)

I think the K2 still used the -004 part Graham but question is did the manufacturer change the design?

Any metallurgy gurus out there?  ;)
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Nurse Julie

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #6 on: September 19, 2018, 04:19:50 PM »
Not the first part used with a number ending in 004  ;)

I think the K2 still used the -004 part Graham but question is did the manufacturer change the design?

Any metallurgy gurus out there?  ;)
I thing Trig is in the workshop Ash, rummaging around in crates trying to find the one that came out of his K0, he may be some time !!!
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Offline AshimotoK0

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #7 on: September 19, 2018, 04:30:01 PM »
Not the first part used with a number ending in 004  ;)

I think the K2 still used the -004 part Graham but question is did the manufacturer change the design?

Any metallurgy gurus out there?  ;)
I thing Trig is in the workshop Ash, rummaging around in crates trying to find the one that came out of his K0, he may be some time !!!

Whoops ...hope I am not in the doghouse Julie  ;D ;D :-[ :-[

Thought I would post it as there are a few low miler 500K0 imports around that DK & Freddie brought in.  Evidently, Honda were obviously aware of the problem and the gear selector issues but didn't recall  bikes still being sold new and in early '72 were trying to shift the old ones alongside the K1's. Hence the legal action against them.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Nurse Julie

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #8 on: September 19, 2018, 04:40:50 PM »
Not the first part used with a number ending in 004  ;)

I think the K2 still used the -004 part Graham but question is did the manufacturer change the design?

Any metallurgy gurus out there?  ;)
I thing Trig is in the workshop Ash, rummaging around in crates trying to find the one that came out of his K0, he may be some time !!!

Whoops ...hope I am not in the doghouse Julie  ;D ;D :-[ :-[

No, you're OK Ash, he seems to be resident out there at the moment......lots of engines arriving for overhauls over the winter, so he has lots of stripping and assessments to do and I have lots of typing to do......we don't communicate much at the moment 😀😀😀
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
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Offline Seabeowner

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #9 on: September 20, 2018, 01:17:36 PM »
Trigger once showed me 550 version, where there is a little trochoidal oil pump built into the bearing assembly ( I think Oddjob had told me about that mod too).

So if you have a early 500 and have the bottom end apart it would be prudent to check out that bearing and the mainshaft it runs on.
Ash, isn't the trochoidal pump is fitted to the end of the other shaft on the 550, the one that had the regularly spaced rollers, 286 p/n bearing. This was replaced by 91022-374-003 + the pump. The bearing 23931-323-004 was retained right through the 550s.
I wonder when the problem surfaced. My K0 is VIN 23k from 7/71, but at least I have a spare later 500 bits, just in case. I suppose there must have been a 23931-323-000 at some time.
« Last Edit: September 20, 2018, 01:19:36 PM by Seabeowner »
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Offline AshimotoK0

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #10 on: September 20, 2018, 06:24:55 PM »
Trigger once showed me 550 version, where there is a little trochoidal oil pump built into the bearing assembly ( I think Oddjob had told me about that mod too).

So if you have a early 500 and have the bottom end apart it would be prudent to check out that bearing and the mainshaft it runs on.
Ash, isn't the trochoidal pump is fitted to the end of the other shaft on the 550, the one that had the regularly spaced rollers, 286 p/n bearing. This was replaced by 91022-374-003 + the pump. The bearing 23931-323-004 was retained right through the 550s.
I wonder when the problem surfaced. My K0 is VIN 23k from 7/71, but at least I have a spare later 500 bits, just in case. I suppose there must have been a 23931-323-000 at some time.


Yes ...you are right,the bearing which was fitted with the pump is the counter-shaft and the -04 part number was still listed for the mainshaft bearing. My K0 parts book is the K0/K1 combined version. Perhaps there was a 71 earlier version of the parts book  which had the main-shaft bearing listed as a different number. I always thought that the -04 denoted the manufacturer though
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline K2-K6

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #11 on: September 20, 2018, 07:03:51 PM »
Have you got any photos of the bearing and what goes outside that also?

At a rough guess without seeing it,  it would appear to be wrong design which would tie in with your observations of revised replacement.

If you have pairs of crowded rollers,  it's possible that one of the pair when under duress will gain "traction" on the other and try to rotate backwards which would cause it to try and clutch the shaft similar to the starter sprag arrangement.  As it has no ramp it won't be possible to pinch fully but could cause surface damage to the shaft.

Generally if you look at crowded rollers at high load (like a car propshaft uj)  they just shuffle back and forth but are dimensionally really stable, also lasting a long time.  They can also make use of different lubricant to make sure friction doesn't exceed load.  Those conditions don't exist here, which leads me to suspect they made a mistake.

Don't know why they'd spec a partially crowded roller in the first place though, if that's what it is.

Offline SteveD CB500K0

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #12 on: September 20, 2018, 08:08:29 PM »
We should move this to “Anorak’s Corner”

What’s a crowded roller?


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Offline K2-K6

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #13 on: September 20, 2018, 08:33:11 PM »
It's just that when separated by a cage to keep them from touching each other "caged roller " compared to the bearing being filled with rollers around its whole circumference with each roller touching it's neighbours,  "crowded roller" type.

You usually associate caged with higher speeds and fairly consistent rotation,  and crowded to take more loading combined with lower speeds and perhaps intermittent rotation.

This one......the original from the description........ Looks to be a half and half hybrid, possibly to try and increase load capacity without changing engine design. Possible if it's shared with smaller gearboxes, but maybe not detected during endurance proving, ie seems to work but out in the real world starts to fail.

Offline Rob62

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Re: Warning to 500K0 owners--dodgy mainshaft needle roller bearing
« Reply #14 on: September 20, 2018, 08:35:52 PM »
I dont know what the original bearing design was... but the surface looks indicative of burnishing i.e. the bearing dragging rather than rolling over the surface due to either failure or lack of lubrication, or probably both

 

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