Replaces previous post, I did not intend to post anonymously- sorry!
I have just converted my 1974 Sprint Veloce (series 1) to 12v using SIP part 500015000. The bike was previously 6v points ignition and now is 12v electronic. It runs ok and I used it 2-up a short run last week. It was a little sluggish on the hills though so I thought I'd try a couple of timing adjustments to see if it made a difference.
Bear in mind that there are no timing reference marks on the case or flywheel cover. The only marks are the PX-style A and IT marks on the stator plate which I understand to be 23 BTDC and 19BTDC respectively. Stock timing on the Sprint V is 22 BTDC so with an electronic set up, 177 kit and sports pipe I'm aiming for 19 or 20. So you can visualise how things are with the plate mounted, at the moment with the stator in position the slot marked A/IT is about 7 o'clock and the pick-up about 8.30.
I carefully used a degree disc and piston stop to find TDC. I know this is correct; if you rest a screwdriver on the top of the piston and turn the flywheel it is the exact point it reaches its zenith before beginning to sink into the barrel as the piston starts its descent. I marked a reference point on the flywheel fin and also on the case. Using a degree disc I then marked a second point 20 degrees to the left of TDC (anti-clockwise). I then started the scoot and using a timing gun looked at the marks - only to find the firing point almost at TDC and miles away from the 20BTDC reference point. I have repeated the same exercise many times from beginning to end with exactly the same result. Rotating the flywheel within the tolerance of the adjustment slots would give me nowhere near enough play. I thought I might have put the stator plate on wrong but rotating it so that the slots align with a different hole would effectively retard or advance by about 120 degrees, which is far too much. I am beginning to think that either I'm going nuts (but I know TDC is correctly marked) or the strobe is wrong ( ..but it can't be!). Surely it wouldn't even start, let alone run if timing was out by almost 20 degrees?
I'm hoping I've made a glaring error that someone will spot. If I am right then the only fix I can see is carefully marking and redrilling the plate 15-20 degrees clockwise from the existing slots forcing an anti clockwise rotation to advance the timing by the same amount when I screw it on using the new mounting points. Something tells me I shouldn't need to go to this length and that there is a simpler answer. Anyone experienced this before? I managed to find an old post about the Bajaj kit and a similar problem with a sprint(similar but different )but nothing specific to this kit. Is there something different about the flywheel/stator relationship on sprints that requires a 20 degree offset from say, a PX 150?