Modern Vespa

Try as I might, I can't persuade the cylinder cowl to stretch over the flywheel cover now I've fitted a longer crank. This leaves a half inch gap where the cooling air can escape. Is this a problem?

Probably not the crank causing that did it fit before? Maybe something changed on the extension nut or cylinder stud the cowl secures to?

Definitely the longer crank, naturally the whole cylinder sits a little higher.

Doubtful 3mm = 0.11811" if you added a 1.5mm spacer to compensate for the stroke that's only 0.059" gotta be something else. Is it interfering with the exhaust clamp?

That flywheel cover looks like a 200 one…

The height from the casing to the head is around 7mm more than with the standard crank, hence the need to fettle the cowl. Other learned forum members have managed with zip ties and washers, which I can also use, but I don't think it will help bridge the gap between the cylinder cowl and flywheel cover.

It's an aftermarket cover for 125/150 models and fits fine thankfully.

Ok maybe you're using a longer rod in your build than the standard 105mm? The stroke alone isn't causing the issue but a longer rod and cylinder spacer would. That's new territory for me unfortunately I don't have the answer. Maybe a P200 cowling fits? Hopefully someone has the answer.

i think you have a poor fitting after market cowl. 57/60 rod will not make a difference. purchase a quality cowl and all is well with the world.

Looks like he's running with a longer 110 connecting rod and 5mm cylinder spacer.

There's some recommendations in your original build post on how to deal with the cowling.

Time for an engine update?

It's the original LML cowl that came new with the scooter. It fitted fine with the original crank but understandably not with the longer type.

Correct. I've managed to secure the cowl satisfactorily using the suggestions in the other thread, but I would like to know if I should try and do something to cover the gap between the cowl and the flywheel cover, or maybe it doesn't matter.

I have a 60 mm crank on my Stella engine fitted with the original covers. I'll have a look at it. Seems like it contacted the cylinder head fins and melted through in one spot. I don't remember a gap but I'll have a look. Same chrome flywheel cover and grey cylinder cover. I would want to close the gap somehow. Maybe a plastic notebook cover, cut up a 5 liter oil jug, some pop rivets until you can find something better. The Stella covers are kind of janky.

Thanks - I have a Piaggio cowl coming in the next day or two, I'll see if that's any better. Otherwise I'll fab (bodge!) something up like you say ...

No, that space isn't ideal.

I've had to persuade a 200 cowl to fit over a bigger-than-standard cylinder head (mrp) on my P2, and that was mostly done by using a screwdriver as a lever and a heat gun. The hard part is getting the plastic hot enough to stretch, but not so hot that it just melts and gives. I've also had to cut out and patch cowls for centered spark plugs (soldering iron and heat gun used), and it seems to hold. Maybe you could try making one with 2 cowls; just make sure the finished cowl isn't under too much tension in either direction: that will be its weak spot.

Thanks, I'll have another look at what's possible when the new cowl arrives. Nice work btw!

that's a lot of work.

https://www.sip-scootershop.com/en/product/cap-spark-plug-hole-cylinder-cowling-vmc_15262700?usrc=vmc

Naw, I was aware of those plugs but wanted something permanent.

Problem solved! I ordered a genuine Piaggio black plastic cowl (part no. 843530) to replace the original grey LML one, and it fits perfectly. The screw near the exhaust stub lines up without any shenanigans and there is no gap between it and the flywheel cover. Even the sparkplug hole is in the right place (I had to oval the LML cowl to fit the plug). The only thing I need to find is a 20mm or so M7 bolt to replace the standard 16mm one that goes into the extended cylinder nut.

Awesome when things work out how do the upgrades feel?

Yup.

There you go!👍

Still messing around with jetting, hopefully all done this weekend. So far, so good!