Honda CB500 K1 engine noise

[Skwid]

I’ve got a CB500 four K1 bobber, when I open the throttle at low speed in any gear there is a noise I can only describe as sounding like a chain slipping on a sprocket or two sprockets not meshing properly, it doesn’t affect performance and only does this at a low speed, it also does it if I put it in gear hold the brakes on and slowly let the clutch out to biting point, drive chain is adjusted front and rear sprockets are good and cam chain is adjusted, any ideas welcome.
I hav Ben offered a complete CB750 bottom end but I don’t know if my top end will fit.

[Trigger]

Welcome to the mad world of the SOHC.
The noise is most probably the primary chain chewing through the main oil gallery and for fitting a  500 top end to a 750 bottom end, no way 

[matthewmosse]

Worth dropping the sump to check it's not the primary chain eating through the oil gallery. Fraid correcting that's and engine out, split the cases job. At least checking it's not eating through the galley is fairly quick and easy, about 11 x m6 bolts  and an oil change. The sump uses an o ring so not even a gasket to change.

[deltarider]

I'm almost sure the chain must be eating into the case on my bike (>135.000 km). Sofar I have not read about or seen any case where the oil supply was indeed compromised, so I decided - foolishly maybe - not to worry and I volunteered to be a guinea pig, so to say

[Trigger]

If you have never seen, then you have not worked on enough CB500 engines 



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[deltarider]

Point is I've read a couple of times that owner's, that had replaced the primary chain, had the noise reoccur in a short period of time. I should add I have (a little) hope that Honda - aware of the 'problem' - has modified the production somewhat on CB500s that were on the assembly line in 1976.

[Bryanj]

Nope, the 550 is recast slightly and is not quite as bad but still its. It was only the 650 that was redesigned with a tensioner.
Oh and whilst in there change the cush rubbers in the primary driven unit.

[Trigger]

And don't forget the cush rubbers 

If racing one of these engines you can go through a chain in 4000 miles or less but, race engines are always stripped and rebuilt after 3 to 5 races 

[Trigger]

And don't forget the cush rubbers 

Damn, I forgot to mention the cush rubbers 

Is that all 8 of them 

[jon stead]

Well this post saved me asking about my noise as the OP could have been written by me about a similar noise coming from my engine in the same circumstances.

I understand it’s engine out and split the cases to renew primary chain and Cush rubbers but can the cases be split without dismantling the top end? I.e. can the engine be turned upside down and the bottom case lifted off?

[jon stead]

Yes but you'll need to remove the cam to allow the camchain to be removed with the crank. You'll also need to split the conrods away from the crank but that's not hard.

Thanks Oddjob, that’s maybe my task this next winter. Don’t intend to do many miles during the summer but would like the bike available for the odd sunny day.

[Skwid]

Thanks for the info fellas, looks like I got a bit of work to do later in the year. As kind as I can get out to a few local shows I’ll be happy.

[Bryanj]

You are in Reading not far from Gloucester.

With all required spares to hand bring me the engine by 9am and take it home done late afternoon BUT this is if nothing extra is needed!

[Trigger]

You should know by now Bryan, there is always something else 

[Bryanj]

Yup but waiting for the one that proves me wrong mate!!!!