Broken cam chain

[Richie 550/4]

Hello all.

New member here, looking for help/advise.

My cam chain has busted on my new toy😩
I am having trouble finding a new top cam sprocket. Anyone out ther got any suggestions?
I've tried David Silver, CMS, Wemoto and have generally searched the internet, but. To no end.
Any suggestions would be greatly appreciated.
Many thanks
Richar

[Nurse Julie]

Tell us more...why do you need a replacement cam sprocket and what other damage occurred internally when the chain let go? Is it a split link chain or endless? Why did the chain let go and where did the chain end up 🤔🤔🤔

[Bryanj]

If you feed me enough beer vouchers i have a NOS one but am away for a week from Tuesday.
How many bent valves/ broken valve guides are there in the head?

[Richie 550/4]

Hi all.

Thanks for the response to my cry for help!

I am having trouble with posting a reply. So if 3 appear I do apologies.

It seems so far that the chain broke on a link and has done no extra damage other than taking the guide out with it. The top sprocket is damaged on the teeth edges and I have not got to the bottom one yet. Next job is to split the crankcase and have a good look around at what may need doing whilst in there retrieving parts.

Thanks for the offers Oddjob and Brynanj if either of you do dig a top sprocket out of your stored, I would be very happy to part with beer tokens for your efforts. Let me know if you have any joy on that front.

Richard

[Greg65]

Ouch, I feel your pain. As you say strip and assess and take the opportunity to replace all your oil seals while it’s apart. Hopefully you’ve found the good Nurses rebuild thread, a great starting point for the rebuild. At least you won’t be bored this winter.

Fingers crossed for you,
Greg

[Bryanj]

If the engine was running when the chain broke there has to be bent valves as there are always some valves open and the pistons will hit them.
The bottom sprocket is cast as part of the crankshaft and not replcable seperately.

[Greg65]

Small point Richie. The post I was referring to was a 400 rebuild, due to a night shift I managed to wander into the wrong section! Interesting with good general principles but not technical. I will now return to my 400 corner.

Cheers,
Greg

[Richie 550/4]

Hi all

Update:

Bryanj. You were absolutely right, I do indeed have a couple of bent valves.

Greg. Yes I did read the rebuild post by Nurse Julie. Very interesting.

It seems I may have other issues too. A friend has had a look over the parts and there are other areas of concern. It would appear the fellow that did the top end rebuild on this machine recently before I purchased the bike had cut a few corners on the rebuild.
General opinion is that I have bought and subsequently opened a big can of worms.

I bought this bike to go out and enjoy with my son who is 21 and rides his..... Cow O Saki ?? I think they are made by Bovine Japanese Alchoholics or something like that. But upon finding these issues it is looking like I will be putting the bike to bed for winter.

Since I've had it I've already rebuilt and cleaned out the carbs and tank as they were both full of debris. And now I'm into a full engine rebuild!! So much for getting out with the boy!

i will keep any interested parties up to date as and when things progres. Got to take the cylinder block, head and rocker cover in to have it all measured to see if we still have something worth working and spending more money on!

Hope I haven't bought a pretty lemon!!!!

Richard

[Bryanj]

Nearly everything is available to rebuild those so go for it

[Richie 550/4]

Hi Bryanj

The main problem it seems I may have is that the cam seats may be worn and it is suspect that some of the rocker arm spindle seats may also be worn. Couple that together with what we may find in the bottom end and it's looking as though it could be an extremely expensive rebuild.

It would be good to know if any of the later model lumps would fit straight into my 1976 frame?
I am maybe looking down the route of a later doner bike that I can rob the engine and rebuild before fitting back into my new/useless toy.
 
Any info on this as an option would be greatly appreciated.

Richard

[Laverda Dave]

I think before I invest in another engine of unknown condition I would strip down your existing engine first to determine the condition of it and to determine what is salvageable and go from there.  If you buy another engine it will be at least 30+ years old, countless owners, probably no history and you could slot it into your frame and get the same results.

To be realistic, there are probably a couple of months decent weather left to go riding, it will take you that long to find a donor bike/engine and slot it into your frame. You would be better off stripping your engine down before the weather gets bad, seeing what you need (the cost will go on rising!) and start gathering the bits together for a rebuild.  As Bryan has said the bits are out there to rebuild these engines and what else are you going to do over the winter whilst the O/H is watching Strictly on the TV? You could spend it in a cold garage getting to know the innards of your motor and come spring it will be rebuilt and you'll be proud of what you have achieved .

The best thing about this forum is the number of experts on here, advice is free and willingly given, all we ask for is plenty of photos (we like photos over the winter months to keep us all going ) and the occassional donation to keep this great forum alive and kicking.

Good luck with whatever you decide to do.

[paul G]

I think before I invest in another engine of unknown condition I would strip down your existing engine first to determine the condition of it and to determine what is salvageable and go from there.  If you buy another engine it will be at least 30+ years old, countless owners, probably no history and you could slot it into your frame and get the same results.

To be realistic, there are probably a couple of months decent weather left to go riding, it will take you that long to find a donor bike/engine and slot it into your frame. You would be better off stripping your engine down before the weather gets bad, seeing what you need (the cost will go on rising!) and start gathering the bits together for a rebuild.  As Bryan has said the bits are out there to rebuild these engines and what else are you going to do over the winter whilst the O/H is watching Strictly on the TV? You could spend it in a cold garage getting to know the innards of your motor and come spring it will be rebuilt and you'll be proud of what you have achieved .


The best thing about this forum is the number of experts on here, advice is free and willingly given, all we ask for is plenty of photos (we like photos over the winter months to keep us all going ) and the occassional donation to keep this great forum alive and kicking.

Good luck with whatever you decide to do.

+1 on the above. Go for it

[Bryanj]

500 engines are getting scarcer but a 550 will fit as long as you use the 550 rh rear engine mounting plate

[Colonial-Clive (yindi)]

You could also go for the 650 engine I believe it don’t take much to for them.

[matthewmosse]

Personally I would drop another lump in there, but, that depends on availability, when I last was in the buying market a motor with good compression and free turning was £150  plus delivery, tested was double that. Given the cost of a gasket and seal set and any parts it was a no brainer, and because delivery was quite a big lump of cash and the bikes worked hard I just bought  an engine or 2 if I had  an issue.