Broken cam chain equals bent valves?

[newc4]

I'm considering picking up a SF with a broken cam chain. The ad says that "Blew the cam chain, not sure why! I didn't hear any noise at all when it blew".

What are the chances that some of the valves are bent? If so, what do I need to replace, besides valves, and what is the availability of parts?

Thanks,
Darrell

[XSPastor]

If the cam chain busted when the engine was running, I'd say the chances are about 100% that some(all ) the valves were bent. A compression check is the best way to tell without disassembling.

[XSPastor]

Just read the rest of your question...

If the chain broke with the engine running at high rpm, there could be damage to internal parts like the chain guide, chain tensioner or the cam and crank sprokets. You should be able to find the parts. I think Vesra still makes the valves and there are plenty of guys parting these engines out on fleabay. I'm sure others with chime in with their opinions/experiences...

[XSPastor]

I hate typos...

[fredintoon]

If the cam chain busted when the engine was running, I'd say the chances are about 100% that some(all ) the valves were bent. A compression check is the best way to tell without disassembling.

Hi Tim,
if the camchain is broken the camshafts won't turn and some of the valves will be held open. Spin the motor like that and a held open valve that isn't bent soon will be. OK, remove the camshafts so all the valves will close before doing a compression test? With no air getting in you won't get a good reading anyway. I don't see any guaranteed check short of pulling the head.

[XSPastor]

Hey Fredintoon,
Duh! You're right!! Of course you can't do a compression check with a broken chain! What the heck was I thinking? I'm going to get another cup of coffee.

[prometheus578]

Valves can be found.. new or used.
Vesrah makes a gasket set... you'll need a new head gasket after pullin' the head to replace the valves.
And yeah, ya probably have a few bent ones.
Shouldn't really be anything more damaged other than the valves.
Ok, maybe a "valve nick" on the top of a piston.
Need a new chain and master link, too.

[egsols]

Having heard the comments, I hope the price is right.

[TopCatGr58]

If the engine was running at even just a fair rpm, the speed of the pistons slamming into the valves would be substantial, and there can also be damage to the valve guides, a bit tougher to replace than just the valves themselves!? Good Luck!
T.C.

[Poprock]

The shoulder bolts backed out of the exhaust cam sprocket on my bike, just as I pulled up at a stop sign. Bent one intake valve. No other damage. Swapped in a valve out of another head, lapped it in. Motor seems to be fine. I'll know more when the carbs are cleaned up. I suspect the fix won't be too severe.

[Toolmaker Tim]

Bent Valves

Darrell, Cycle Recycle 2 in Indianapolis, In is where I got my replacement valves for the 2 bent valves, plus the two I bent setting the camshaft-valve shim clearences. The prices were pretty reasonable and service was quick. Just my $.02. The job isn't as hard as I made it for myself. While you are in there you might want to replace the valve seals. Good Luck. Tim

[trbig]

A chain breaking while riding could cause some problems. The cams aren't going to immediately go from 3k rpm to stop.. so they may indeed all be bent. The chain could have become balled up in the bottom of the motor and bent/damaged the crank sprocket or even cracked the case slightly before the motor stopped spinning completely... but it's pretty doubtfull.


andreashweiss on here can probably set you up with a "Newsed" complete head at a really reasonable price.. or just the valves. Worst case scenario.. I think there will be bikes for sale a plenty this winter. Keep your eyes out for a good used motor on a parts bike and swap the whole shebang.

Tod