Post by: AshimotoK0 on September 19, 2018, 02:45:18 PM
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.
Post by: Trigger on September 19, 2018, 03:41:27 PM
Post by: deltarider 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 CB500/4I 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
Post by: AshimotoK0 on September 19, 2018, 04:07:11 PM
[attachimg=1]
Post by: Trigger on September 19, 2018, 04:07:29 PM
Post by: AshimotoK0 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? ;)
Post by: Nurse Julie on September 19, 2018, 04:19:50 PM
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 !!!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? ;)
Post by: AshimotoK0 on September 19, 2018, 04:30:01 PM
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 !!!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? ;)
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.
Post by: Nurse Julie on September 19, 2018, 04:40:50 PM
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 😀😀😀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 !!!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? ;)
Whoops ...hope I am not in the doghouse Julie ;D ;D :-[ :-[
Post by: Seabeowner 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).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.
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.
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.
Post by: AshimotoK0 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).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.
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.
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
Post by: K2-K6 on September 20, 2018, 07:03:51 PM
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.
Post by: SteveD CB500K0 on September 20, 2018, 08:08:29 PM
What’s a crowded roller?
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Post by: K2-K6 on September 20, 2018, 08:33:11 PM
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.
Post by: Rob62 on September 20, 2018, 08:35:52 PM
Post by: K2-K6 on September 20, 2018, 08:55:02 PM
If the problem doesn't occur with a revised bearing it indicates the design of the first was wrong rather than the lubrication.
Post by: AshimotoK0 on September 20, 2018, 09:14:40 PM
[attachimg=1]
Post by: Trigger on September 20, 2018, 09:22:37 PM
Post by: AshimotoK0 on September 20, 2018, 09:32:33 PM
[attachimg=1]
Post by: Rob62 on September 20, 2018, 09:56:25 PM
Post by: K2-K6 on September 20, 2018, 10:05:17 PM
That definitely looks like it could give a sprag clutch effect on the shaft. If you think about it travelling around, the two rollers at their interaction with each other are going in the opposite direction while the bearing is rotating. In a whole crowded race, each successive roller is subjected to the same and equally opposing forces. It'll give friction which is why you'd head away from that for higher bearing rotation speed and toward a caged roller design to avoid that.
But that paired roller design seems to be ok as long as tolerance is tight from inner to outer race, including roller dimension. But if you got any wear at all, then one of the pair would want to climb over the other and so set up a sprag clutch effect. Ultimately it would try to grab the shaft but without enough room to shift it's geometry sufficiently it should rapidly build heat and/or damage the shaft surface.
Oil film doesn't servive in a sprag clutch as that is exactly what the mechanical ramping effect is supposed to do, break down the lubricant until fraction bites the shaft and makes the components pinch each other to cause torque transfer.
Post by: Bryanj on September 21, 2018, 04:16:50 AM
Post by: Trigger on September 21, 2018, 08:35:00 AM
A member on this forum has a UK, 500K0 that has a locked engine at low mileage and i suspect that this engine lock is due to the shaft problem.
Post by: deltarider on September 21, 2018, 08:46:35 AM
All the K0 shafts i have had problems with were all blue due to over heating. The other problem was a few had the oil guide plate missing ( PN 23106 323 000) and CMS list this plate on engine number 1018728 onwards. With out this plate the bearing was also burnt out and some had damage to the casing.I have the feeling this oil guide plate 23106-323-000 is of crucial importance. I always wondered why it was added like in mine and was not present in the early models.
Post by: AshimotoK0 on September 21, 2018, 12:33:57 PM
Ash, what is the part number in the Japanese parts book?
Its at work Bryan ...I still need to scan it... I will check when I am next in. need to give you a call by the way...when is the best time please?
Post by: Bryanj on September 21, 2018, 03:26:53 PM
Post by: K2-K6 on September 21, 2018, 03:34:49 PM
All of the shaft problems i have seen, have been on early K0's and nearly all have been around the 5.000 to 7.000 miles ;)
A member on this forum has a UK, 500K0 that has a locked engine at low mileage and i suspect that this engine lock is due to the shaft problem.
Could you try with it in gear to push it backwards and see if it moved? If it has "spragged" it may release it.
Or pull the clutch pack out of it to disconnect the motor from the main shaft completely, then try to turn it over to see if it's unlocked.
It would tell you if it's hanging up on that bearing or not.
Post by: AshimotoK0 on September 21, 2018, 05:31:57 PM
Post by: K2-K6 on September 21, 2018, 08:16:56 PM
Sounds like it could be the same thing, 4th post from last on this page.
Post by: AshimotoK0 on September 22, 2018, 09:51:24 AM
Ash, what is the part number in the Japanese parts book?
I just checked your Japanese parts book Bryan and it was published in 3/1971 so must have been the very first parts book for the CB500K0 and the bearing number for the main-shaft is exactly the same i.e. 23931-323-004.
I will talk to you next week when I call you about scanning it.
Post by: AshimotoK0 on September 22, 2018, 10:12:41 AM
https://www.davidsilverspares.co.uk/parts/by-part-number/partnumber_23931323004/
Unfortunately nobody seems to have the countershaft needle roller bearing at a reasonable price. 91023-286-016
Post by: K2-K6 on September 22, 2018, 01:42:44 PM
Ordinarily you'd guess the reasons for change would be chasing load capacity and/or durability. But why a paired roller? I'm at a loss to see a rational path to that design. Must be something we're missing, I don't recall seeing another of that type though across many different applications. They have plenty of things to play with in shifting roller number and size, but why pair them?
On a slightly different, but related note, just going through some old bike magazines and CMM March 2011 has a picture of a proud 400 Four owner, is that you Ash?
Nigel.
Post by: AshimotoK0 on September 22, 2018, 06:19:09 PM
Like you Ash and Rob62, I don't understand why they've specified a strange bearing there.
Ordinarily you'd guess the reasons for change would be chasing load capacity and/or durability. But why a paired roller? I'm at a loss to see a rational path to that design. Must be something we're missing, I don't recall seeing another of that type though across many different applications. They have plenty of things to play with in shifting roller number and size, but why pair them?
On a slightly different, but related note, just going through some old bike magazines and CMM March 2011 has a picture of a proud 400 Four owner, is that you Ash?
Nigel.
Yes that was me but the bike is back to it's original Varnish Blue now. That article was by Mark Williams and he got loads wrong... e.g. I was restoring a rare sandcast 750 ...it was actually UK K0 diecast but hey-ho.
Post by: Trigger on September 22, 2018, 09:50:47 PM
You can get the needles on there own from any good bearing supplier ;)
Post by: matthewmosse on September 23, 2018, 12:19:54 AM
Post by: Bryanj on September 23, 2018, 10:47:14 AM