advance unit springs

e3steve · Post by **e3steve** » Wed Dec 09, 2009 2:35 pm

Wilf, your rationale stands up to scrutiny well enough, but 'tightening' the springs won't actually restrict the total advance, as you state; it will merely delay it until higher RPM. Perhaps removing two (or three) turns of the coil and bending up the third (or fourth) into a hook may eventually offer enough resistance to overcome the advancer weights' natural desire to centrifugally 'spin out', but the only way to be certain is to mechanically restrict the movement of the advancer pegs (that originally accommodated the neoprene stoppers).

I can't weld either -- at least, not well enough -- but, in a situation such as yours, I would attempt drilling & tapping a small (M4?) hole right on each "max advance" edge of the pegs' apertures and cut a pair of screws to length (about 3mm?), allowing the heads to act as restrictors. Too much restriction: file the edge of the head; not enough restriction: fit a washer and file that to suit. Use a good thread-locker though!

But replacing the neoprenes would be a more desirable route to success, I'd say.

Wilf · Post by **Wilf** » Wed Dec 09, 2009 4:00 pm

Hi Steve,

It's good to hear your input on our situations. I have a big question--how is it possible to replace the neoprenes? That would indeed be the ideal fix but I don't know how to do it!

I'm looking hard for solutions..

Wilf

e3steve · Post by **e3steve** » Thu Dec 10, 2009 3:58 pm

Sorry Wilf, out of my depth on that one, I'm afraid! I believe the only way is possibly the replacement of the sprocket. How about trying some good quality oil-resistant heatshrink tubing? Like, 2 or 3 pieces, one over the other; shrink the first down (use a heat gun, not a flame!), pare of the excess and add another piece.

I reckon the only reason for the pegs being fitted with a 'soft' covering is to prevent the weights chattering at idle and just above, as at full-advance they'll be hard against the apertures' circumferences.

Wilf · Post by **Wilf** » Thu Dec 10, 2009 5:38 pm

Steve, you've read my mind once again. I had thought of the heat shrink tubing but I wondered if it would hold up against the heat and mechanical strains. I had visions of bits of the tubing flying off and floating around who knows where in the engine.

I've tightened up the spring loops but realizing that is not the cure, I'm now looking into a replacement sprocket. I didn't really want to pull the cam apart but that seems to be the only way to really address the problem.

Thanks,

Wilf

davomoto · Post by **davomoto** » Thu Dec 10, 2009 6:05 pm

Here are a couple different approaches that I have mined out of motors in the past. The one on the left has has stop welded to advance inital timing. The one on the right is brazed open at full advance, most likely a racing engine.

davomoto

Wilf · Post by **Wilf** » Fri Dec 11, 2009 9:34 am

Thanks for posting the pics davo...I've never seen one of these units out of the engine, but I guess I will in a couple of days when I pull mine out.

e3steve · Post by **e3steve** » Sat Dec 12, 2009 4:49 am

I didn't really want to pull the cam apart but that seems to be the only way to really address the problem.

"Do it right, you only need to do it once!" is one of my mantras, along with "treat others as you would wish to be treated yourself" and "honest men know that revenge does not taste sweet"... (the last taken from a great '70s song -- no prizes but let's see who gets it!).

It's a problem that needs to be open to experimentation. On a personal note, and in a similar situation as yours, I would give it a try. That's not to say you should but, for me, the challenges are all part of the fun of ownership of the entire historical package; it's not all about the riding. My experiments with the charging system have, thus far, stood the test and are testimony to that rationale.