Camshaft broken

8O
I took the valve cover off this locked up 650 engine I have just to poke around and learn more about this mill. The intake cam was broken in half in two places... Does anybody have any suggestions as to HOW this happened? Maybe the PO tried to start it after it was seized?

Almost all the intake valves are seized due to sitting open to the rain with no carbs, so this head is scrap metal for sure. I'm curious to see how badly the rings are bound to the cylinders. It'd be nice to salvage this engine instead of springing for a different one, but so far it's a boat anchor.

Also, I can't get the head off. I don't have a manual of any sort, but after searching this site I've taken the nuts off the top side around the plugs, the two on the underside in the front, and a couple under the back side close to the YICS rail. Does that sound like all of them, or is the thing just stuck?

 

Wow. Just, wow.

Was there rust damage?

I mean, it is aluminum, but... Surely the starter motor doesn't have enough torque to do that, right? Or we would have heard of something like this before.

 

It depends on what the breaks look like; if they're rotational ("twisted") then it happened under power.

It could also have been done by somebody tightening the cam caps down and forcing the cams against against seized valves that they couldn't push open.

Before you go to too much work, drain the sump. If you get rusty water out instead of oil, don't bother. If the bottom end and transmission are rusted internally, it's beyond salvation.

And you will need a service manual.

 

Most overhead cam engines break cams when the cams starve for oil. The cams heat up and the aluminum starts to gall and bingo the cam snaps.
Bad oil pump or just run low on oil would be my guess.


MN

 

I didn't figure this was common... thanks all.

 

It isn't. Common, that is.

 

Well, I've already dumped the "oil" when I first got the bike. There is probably no hope for this engine. Mostly water came out, very little gray oil sludge. This leads me to believe it was probably ran without oil, which broke the cam in the first place. The water is just an extra kick in the teeth. I had an old '60s AMF Sprint 350ss that came with a case full of water, but it actually turned over with a wrench without issue after I drained it. I can't get this one to turn over with a 4ft. breaker bar.

Thanks anyway folks. I'll search for another engine and just play with this one.

 

Last Rebel, where are you located? I have a 650 engine here......central NY near Utica. PM me if you're close.

FWIW, I just parted out a 550 engine that had a broken sprocket on the cam......engine ran great, had good compression, etc..... when I opened it, I was suprised to see that. PLUS, the chain was still in line, tight, etc......no indication anything was wrong. Til I saw it myself.

dave f

 

Hey Dave, I'm the guy you talked to about the 550 carbs. I'm in Georgia, a bit of distance between us. Thanks though!