Topic: cb550/650 primary chains: has anyone here actually seen one break?

[paulages]

hy-vo style- seem pretty damn strong. i have one from a very low mileage 650. i was planning on buying a new one, but really, do these even break? it's within spec length.

[scunny]

I never measured the length but could tell comparing 2 650 chains hanging from a nail which had the least mileage, the high use one drooped more, not scientific but will do me 
looking at their construction I would be surprised if breakage would be an issue

[paulages]

the 650 case has a primary chain tensioner. as much as i modified the 550 case already, i had to draw the line somewhere. if i had a tensioner i'd worry less, but with the added power i think a new primary chain is definitely in order... but comparing to the 750 chains, i just had to wonder whether the same concerns apply.

[bryanj]

They dont break BUT on the 500/550 they do get slack enough to eat through the oil galleries

[paulages]

They dont break BUT on the 500/550 they do get slack enough to eat through the oil galleries

you're who i was hoping to here from, bryan. about what mileage is this common with? i kinda wish i had added in the tensioner that the 650 has, but part of the design is cast into the case.

[scunny]

on my high mileage motor the primary chain had caused a fair amount of wear on the tensioner, this was on an indicated 75,000k bike

[BSA_Mikael]

No, I never seen one break, but plenty made nice marks in the housing (More or less standard in the CB four family) and would have made any sensible airplane mechanic dismantling the oilfilter and checking the paper for metal signs be so nervous he would tear down most of the engine...)

I have never seen an unscrewed CB 500/550/750 primary or camchain break.

But! I have seen modified/tampered camchain tensioners cause camchain breaks, so I have decided I'd rather put up with some noise..
 

[crazypj]

I have seen the plates break on a couple but bikes kept running fine.(except for strange noise)
I'm pretty sure a single plate would cut through oil gallery quicker than a worn chain though
The pins were still intact so I don't know what caused problem, only one end of plate was damaged and flapping about.
The owners wouldn't admit anything but I suspect something got in there during a service or head/base gasket replacement and caused localised failure?
 I have never seen a total failure where chain breaks completely though
PJ

[kayaker43]

Never heard of one breaking either. It would take a serious shock loading like maybe a drag bike with a slick and not running a rear cush drive. Even then I think the clutch would slip and absorb the shock load? Yoshimura was getting over 70 Hp and I never heard of them having trouble. The tensioner is just one more reason to start with the 650 cases I think.

I would worry more about your rods? Have you done anything there?

[bryanj]

Paul, hard to say on life I seen a worn out one at 25,000 indicated and a useable one at 45,000.

Best thig is if you are down that far fit one, even though they are costly. I do know one of the Kawasaki's is the same but cant remember which one

[paulages]

yeah, i'm fitting one no matter what... i'm not going through as much trouble as i am just to leave out such an important replacement. i was just curious, in part because the 650 donor engine only had 3000 miles on it, but i also because i happened to have 750 and 550/650 primary chains on my bench at the same time. the 550/650 look to be much much stronger than the 750 to the naked eye.

[paulages]

FWIW, i think a primary tensioner could be fitted to a 550, it would just take a little ingenuity to figure out the pad that the tensioner slipper rests on in the 650 case. i bet some high strength epoxy could be shaped to do the trick. otherwise, it's just a matter of welding in a post for the mount.

okay, maybe i'll play around with it...

[Soos]

What about having a block machinied to emulate the slot the tensioner rests in and weld or bolt it into place on the 550 cases?

I don't know if i would trust JBweld or epoxy to hold, if it came loose.....
I'm sure the images are running through your head now....

l8r

[paulages]

What about having a block machinied to emulate the slot the tensioner rests in and weld or bolt it into place on the 550 cases?

I don't know if i would trust JBweld or epoxy to hold, if it came loose.....
I'm sure the images are running through your head now....

l8r

it's not a slot, it's a flat spot that the slipper rests on. there's already a bit of epoxy in use in the case-- no point trying to explain right now, but there will be pictures later. the stuff my machinist used he says they use in engines all the time.