SOHC.co.uk Forums > CB500/550
Help needed to identify my CB500-4
AshimotoK0:
--- Quote from: B11sey on February 07, 2023, 01:36:00 PM --- The K0 needle roller seizing on the mainshaft issue was significant though ... my bearing was well and truly fooked and Graham (Trigger) once showed me a very low mileage K0 countershaft that had been fried by the needle bearing seizing. It's a double-bunched roller type and on mine the alloy carrier cage had disintegrated.
I’ll check mine when I split the cases. Are there any proprietary fixes for the K0 gearbox issues?
--- End quote ---
Yours is a UK / Euro model ... it was probably well sorted out by then. I think the centre shift fork is still prone to wear though so worth checking .. Trigger/Oddjob /Bryan can advise on this better than me.
Here are the Service Bulletins with numbers. from my Dropbox links ... you need service Bulletin #4
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CB500/4 Service Bulletins .. MASSIVE THANKS TO BRYAN JONES FOR COLLECTING THESE AND LOANING FOR ME TO SCAN
https://www.dropbox.com/sh/z8s0vpxu8niqva3/AAC1D8GaKGw_tvX0y2-CTcHaa?dl=0
Oddjob:
What year did the 750k1 come out though Ash? Was it before the 500k0? I’d imagine it may have been as the 750 came out in 69 and Honda never seem to hang about with a new version so probably 70?
I recall vividly the press slating the 500 for its switchgear, you remember me saying one was written off whilst being tested, what if that’s why it got written off? The press rider claims it left him with no lights on a dark road, he goes off the road and hits something, this may or may not be true, he could have claimed this was the reason for the crash when in fact he was drunk, doesn’t matter, Honda can’t afford to take the chance, if they know about it and someone else has an off or worse gets killed they are liable and completely exposed. So what does Honda do? It removes the offending switch and fits a separate one for on/off. They wouldn’t do this without a damned good reason, it’s expensive to change the production line, expensive to have a completely new switch made and tbh it did spoil the look of the handlebar layout with something that clearly looked to be an afterthought. Just looked at the parts book for the 750 and the light switch is a 750 part number and to me it looks like it wasn’t introduced till 71, it shows on the K0/1 parts lists but there is no part number shown so it may have been an addition to the book added later, pics of one taken at the time don’t show one fitted. So not only did Honda change the 500 specs it also changed the 750 specs and that switch is changed for the 550 for a completely different one.
The gearbox fault wasn’t really well known about at the time for that to have been the reason, Honda did know early enough to change the later engines to avoid the problem but that’s info they would have kept secret in order to not damage sales or reputation of the brand.
These are all just theories, until we know for certain it’s all conjecture
B11sey:
Ashimoto
My engine number shows it was made before the gearbox mods so I definatly need to check this
AshimotoK0:
--- Quote from: Oddjob on February 07, 2023, 04:37:26 PM ---What year did the 750k1 come out though Ash? Was it before the 500k0? I’d imagine it may have been as the 750 came out in 69 and Honda never seem to hang about with a new version so probably 70?
I recall vividly the press slating the 500 for its switchgear, you remember me saying one was written off whilst being tested, what if that’s why it got written off? The press rider claims it left him with no lights on a dark road, he goes off the road and hits something, this may or may not be true, he could have claimed this was the reason for the crash when in fact he was drunk, doesn’t matter, Honda can’t afford to take the chance, if they know about it and someone else has an off or worse gets killed they are liable and completely exposed. So what does Honda do? It removes the offending switch and fits a separate one for on/off. They wouldn’t do this without a damned good reason, it’s expensive to change the production line, expensive to have a completely new switch made and tbh it did spoil the look of the handlebar layout with something that clearly looked to be an afterthought. Just looked at the parts book for the 750 and the light switch is a 750 part number and to me it looks like it wasn’t introduced till 71, it shows on the K0/1 parts lists but there is no part number shown so it may have been an addition to the book added later, pics of one taken at the time don’t show one fitted. So not only did Honda change the 500 specs it also changed the 750 specs and that switch is changed for the 550 for a completely different one.
The gearbox fault wasn’t really well known about at the time for that to have been the reason, Honda did know early enough to change the later engines to avoid the problem but that’s info they would have kept secret in order to not damage sales or reputation of the brand.
These are all just theories, until we know for certain it’s all conjecture
--- End quote ---
The 750K1 came out in late 1970 in the US (not sure about UK) so before the 500K0 was introduced .
If you look at the 1st full MCM magazine review of the 750 in June 1970 (attached) you will see that rather than slating the headlamp switch the reviewer was actually in praise of it!
I suppose we will have wait and see if Ian can throw any light on the subject :) . He was the Press release man at Honda at the time and was the rider of the bike that was in the 1st UK brochure. If not, we will just have to keep guessing, as I don't know of anyone else around who was with Honda at the time. Perhaps we were a relatively insignificant market and just not offered the model in sufficient quantities to make it viable to sell here.
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Oddjob:
I think we have to take that review in context Ash, they may be praising the switch as it was so much superior to what the British bikes were offering at the time, I seem to recall they had a switch on the headlight bowl which meant you needed to remove a hand off the bars in order to switch them on, plus it was before the 500 reviews came out and as we know it's defect was pointed out then. As you say though, we won't know for sure until someone who was there says the real reason.
I wonder if an enquiry to one of the magazines of the day, like MotorCycle Mechanics or Bike or any that's still going to see if they know. I'd love to know which magazine wrote one off.
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