Cl125S rebuildâ€”cam orientation on install

Dudley

Hi guys,

On my 1974 Honda CL125 S (single cyl) that I'm doing a re-ring/valve job on, I'm not real clear on the reinstallation of the camshaft for proper timing.

Let's say I've finished the valves, reinstalled the springs, etc, and the head is back on the cylinder, and it is torqued down like the book says. Ok, time to re-install the cam. Easy enough to do. So, ok, it's in, and the bolt holes are vertical.

Here's what I've been able to figure out, and it would be nice if one of you rebuilder gurus could confirm this.

This much I know;
A) The "intake" lobe is the closest lobe to the chain/sprocket.
B) The piston is (or will be) at TDC, which also lines up the mark on the rotor coil.
C) After installation of the cam and the chain (assuming it is correct), if I rotate the crank in proper crank direction, the cam lobe "BEGINS" to open the "intake" valve. Is this correct?

The manual is NOT especially clear on this. It says something about "after installing cam, rotate it "one full revolution" to orient it correctly. WHAT? One full revolution is where you began! ??

Any tips/pointers/confirmation on reinstalling the cam and getting the timing correct would be appreciated!! I did notice that the oil holes on the cam were 'up' if my logics are correct, FWIW.

Thanks, Dudley

Dudley · Posted: Sun Jan 22, 2012 9:35 am Post subject:

Guys,

After a little research, I "think" I'm on the right path, but it would still be nice to have a little confirmation.

Bill Lane mentioned to "Tuesday" a few years back, who has a similar question, "the intake lobe (which is the one closest to the sprocket) should be in the (approx) 45 degree position (or 1:30 position), when the cam is oriented properly."

This is "agreeing" with my analysis, from what I've also been able to figure out.

BTW, this would also place the pin on the cam (for the points base) at the "5:00" position.

Am I on the right track?

Thanks, Mike

05c50 · Posted: Sun Jan 22, 2012 7:24 pm Post subject:

Mike, I don't have a manual for your bike, but I think that your on the rightr track. On a 4 cycle engine, as the piston passes TDC, the intake valve will open to draw the air/fuel mixture into the cylinder to be compressed on the next up stroke. I think you've got it right.

......Paul

Dudley · Posted: Sun Jan 22, 2012 9:27 pm Post subject:

Paul,

Thanks for the reply and concurring with my thinking.

After establishing the correct cam rotation facing the cam gear (counter clockwise), and that the lobe nearest the gear is the intake lobe, and with the cam "O" mark on the cam gear in perfect position to match the "T" mark at the statorâ€”the "slightest" rotation begins opening the intake valve. This leads me to be confident it is correct!! (rotating the cam 180 deg. puts the intake lobe at 7:00 position...and that doesn't make ANY sense at all!!!)

I took a photo of the two timing marks in question BEFORE I took it all apart. The ONLY thing I think I had any question about is getting the cam back in correctly. At this point, I'm extremely confident I have it figured out.

Dudley (Mike)

05c50 · Posted: Sun Jan 22, 2012 9:42 pm Post subject:

Sorry, the picture didn't come through.

............Paul