New cam; Which way is up if no chain?

[stillgar]

Hi, Guys,

I recently bought a Baja SC50 scooter with no compression. I found your board referenced in an ebay ad for a bbk. Excellent illustrated instructions, too! What a great resource you have here.
As soon as I removed the valve cover, I saw there was no timing chain visible. A cam bearing had spun, and the chain was down around the crank. I fiished the metal pieces out from around the crank, and will get the rest out when I drain the oil.

I installed a new cam assembly with the timing mark at the T position (chain was OK), but my question is: How can I tell if the crank was in the right rotation ? There is a lot to re-assemble, and I really have bad luck guessing. Can anyone help me with this? The motor now has some compression, but my trusty automotive compression gauge won't fit the tiny spark plug threads.

Any information would be helpful. Thank you.

[Greg]

The piston is at the top whenever the "T" mark is aligned.
As long as you put the cam in with the two little holes parallel with the side of the valve cover and the big hole facing up, you'll be fine.

When putting in a cam, you are creating "top dead center". Hopefully that makes sense.

You only have to worry about the right "crank rotation" (one of the two "T" marks in the 4 cycles), when adjusting valves because you are either at top dead center (cam holes lined up properly) or you are 180 degrees out (on the cam - and the big hole would not be seen) so you would have to rotate the crank another 360 degrees.

I'm starting to confuse myself, hopefully you got something from this. ;D

[Greg]

Oh and, :welcome3:

[stillgar]

Thanks, gs, for the prompt reply. I got the valves adjusted (.004 both). I hope I'm not overthinking things. I once had to do a head on a 4 cyl. car, and the guy who started the job didn't mark things. I got the cam in wrong, and have bad memories from that. Of course, with only 1 cylinder, you don't have to worry about firing order, and there's no distributor.
I got all the plastics on the motor, and will be installing it soon. The wife will be glad to see it off the dining room table! All I need is a cheap exhaust (didn't come with one) and I'm off.