Modern Vespa

Help needed from some wise people: I know that this is not your first rodeo.

Please indulge this long and rather tedious post.

A few months ago, my mostly standard P200E picked up a starting issue following a clutch side oil seal replacement. The bike ran for a while but the starting quickly got worse and resulted in constant carb' backfires and the occasional actual fire.

As other threads on this forum assured me: TIMING, TIMING, TIMING.

On that basis, I chased the timing all around the dial. Great spark, and because it was electronic ignition (Vespatronic), there shouldn't have been a lot to miss. The flywheel was sat on the crank correctly. No movement from the woodruff key and no signs of wear. Nothing rubbing, clear of the screw heads etc. Torqued down, Loctite applied.

Occasionally it would start and run well, then run rough, then back to carb' backfires. I changed the stator, the HT lead, the CDI unit, the plug, but not the flywheel (after all, it's not powered and has no moving parts).

Elsewhere on the bike:
Clean, fresh fuel.
Good fuel supply to the carb (flows well).
Spotless carb (I tried two).
Airbox on tight, fresh gaskets.
Crank & barrel pressure leak-down test found a slow leak on the base gasket which was cured. Now airtight.
No signs in the oil that anything is travelling between the gearbox and the crank.
Clear exhaust (I have tried two)
Inlet to rotary valve pad leak tested with 2T oil. Worn, but not an issue: it worked before.

So, this morning I wiped away the tears and returned to Modern Vespa.

Same message: TIMING, TIMING, TIMING.

The only component left was the Vespatronic flywheel itself.

I have never known what it is on this flywheel that triggers the ignition coil to fire off its charge. There is nothing distinctive on the inside of the flywheel. There is a mysterious letter 'F', but I cannot see its significance (yet).

Looking online, I could only find two images of the inside of Vespatronic P Range flywheels. What struck me was that both showed the magnets to be in different positions to my own. Using the Woodruff Key slot as a point of reference, both SIP and Beedspeed's images showed the key slot to be opposite a break between magnets. The key slot on mine was opposite a magnet.

The ring of magnets is set in a plastic frame, that has then been pressure fitted into the metal core of the flywheel. Using modest pressure, it would not revolve within the wheel, but it was easy to push out by hand.

Inside of the wheel, there are marks where the magnets were once
positioned. These are in line with the supplier's pictures, but not with the reality of my flywheel now.

There are also marks that would indicate that there has been movement within the centre of the flywheel.

In short, I believe that the ring of magnets has come loose and has been moving sporadically within the flywheel body. That would explain the random nature of the timing and the sporadic nature of the problem.

I'd really appreciate any thoughts on this, because I'm right at the bottom of the ideas barrel.

Particularly:

Does anyone have a Vespatronic flywheel currently off their bike that they could check the magnet positioning for me?

What triggers the crank position sensor? There is one portion between two of the magnets that differs from the other three. (see pics)

Where should the flywheel be in relation to the ignition coil?

I've included a few images that I hope will help. The SIP flywheel picture is from their site.

All help on this greatly welcomed.

And before you ask, I bought the kit in 2020 lockdown, so no VAPEs available.

Thanks, Peter

I'd find the appropriate adhesive and pout them where they are supposed to be.
I assume the stator is fixed. I don't see a trigger but if it's part of that ring and if the stator's fixed you may have to get the position of the magnets perfect. Could you check the timing with a strobe and see if it's out by the same degrees the magnets are ? Looks almost right on 45.

Keyway is at 12, a seam in the plastics is at the 3oclock position.

My understanding of the "trigger" on the Vespatronic is that it's just based on the voltage rise only, so it triggers twice per revolution.

So you also need to line up the N/S to the correct point.

If it were me, I'd take this as a sign to move on to something other than Vespatronic.

That's pretty much the plan. SIP have at least given me something to go on with their listing images. Quattrini don't even seem to have an accesible website (I might be wrong: it's a trend).

I have a 1/4 chance of getting it right first time. Plus their images. Then the adhesive.
Yes, plenty of adjustment on the stator plate for strobing once we're back.
I spent a lot of time extending the wholes first time round.

https://www.sip-scootershop.com/en/product/flywheel-vespatronic_50006310?q=vespatronic

Thanks so much for the image. I haven't smiled for a week.

It'll be tomorrow now: updates to follow.

Very happy, goodnight.

If you were to glue it back into the wrong position, would that mean that you could simply make a new TDC mark and time it 18 degrees (or whatever) from there?

If nothing eventually works. Change to SIP or BGM Vape and Done!

I don't see why not. So long as it's consistent and within the range of adjustment of the stator, should be good-to-go. just gotta be close.

Buy new stator and flywheel. Sell this one as a performance upgrade with infininte variable ignition timing.

360° variable timing…

Part 2

Morning America

Big thanks for yesterday's provision of an image from MJRALLY (sorry, I don't have anyone's real names). I was seconds away from not posting any of this, as it seemed like such an unlikely fault.

Also, thanks to oopsclunkthud for letting me know that I was looking for something that was not there to be found. Top replies: move on.

I've put a few images on. Hopefully, they are self-explanatory.

Today I have recruited the eyes of a young person to help me find the mark opposite the key channel. Then I set the magnets back in the right place and temporarily fixed them with Duck tape.

And she started. I can't tell you how relieved I was. Not mad.
Ran very sweetly out-of-the-box.

I wanted to see if anything fell off, so took a three mile ride: no stops. All good.

On return, I went to strobe it and it would not start. Back to the same symptoms.

Flywheel off and to my delight, the magnets had moved again.

Tonight, the J B Weld has been deployed and we go again tomorrow.

I appreciate that I've given a lot of detail here, but I could not find anything else about this on the WWW. So, if anyone else has the same issue, I hope they find this thread.

Thanks, Peter

Good for you !

you should really use something different than jb weld (I had to)

if it doesn't hold at least you know what you're up against, there has to be some way to get that sucker to stay. JB is a good first guess on how to secure that.