Off-white, round plastic part on camshaft sprocket/gear's function?

[rferrel1]

Does anyone know what the function of the yellowish round plastic part is that seems to be attached to the camshaft sprocket? My '07 215 wake quit running, lost compression on all three cylinders (35 psi each) and BUDS showed a cam position fault. When valve cover was removed, found the yellowish round part was off the camshaft gear and chewed up, timing chain was sloppy loose, and chain guide on the non-tensioner side of chain somewhat worn or damaged. I suspect my timing got off a click or two causing the lost compression. Have new yellowish round part ordered, new chain guide, new tensioner shoe guide and new tensioner all of which I plan to replace. Curious about the function of the yellowish round part that seems to belong on the camshaft sprocket.

 

[Chester]

I think you are in for way more damage than you expect. First off, I think the plastic part that goes on the end of the cam gear is there to prevent oil from escaping through the vent valve, kind of like an oil slinger. The vent valve vents crankcase vapours/blow-by into the intake. Models older than 2006 didn't use that vent valve or the plastic part. On those, the crankcase was vented from the oil separator at the other end of the engine.
Now, the engine damage. You may be in for a complete engine rebuild. Something had to hit that plastic part to damage it. your timing chain might have broke. If it did break, at least one piston will have hit the valves and bent them. Before you pay for those parts, you will have to completely disassemble the engine to determine all the damage. It has to come apart anyways as the only way to replace the timing chain is to remove the crankshaft.
Here's a picture of the damage a broken timing chain do.

Chester

 

[rferrel1]

Thanks Chester. I have the PTO cover off and everything inside it looks perfect. I can roll the engine over by hand without hitting valves. I think my cam timing is incorrect, since I have the marks on the balancer sprocket and the crankshaft lined up and the crankshaft pin seems to fit into the crankshaft. But when I have the crankshaft locked, my camshaft locking pin won't go into the camshaft to lock it in position. We suspected the cam timing was off, since all three cylinders had 35 psi while running it with the starter motor (and it didn't seem to be hitting valves). Still hopeful I haven't hammered the valves.