Modern Vespa

Would it leak past the cylinder stud threads at the head?

Looks to me like the put the O ring outside the studs. This means that compression remains within the sealed area - encompassing the stud bays.

I have a VMC cylinder.
They use the 3 port exhaust.
The side ports are curved in (not optimal) to allow space for the studs to pass.
Any work on those ports risks breaking through.
With the O ring outside the studs, it means they are still sealed.

I think...

I thought these had a 3 port exhaust too. The one in the video is a single port. Is this Explorer the Sport version?

It'd still leak past the washer and nut on the studs.

Also the 4 additional fixing screws.

Unless there's a seal below each washer.

I should really draw something out to visualise it…

Im getting excited about this. The TightRat engine may need one of these

If compression can leak past the nuts or bolts, I was thinking it must happen even if you didn't port.
But perhaps I have it wrong.

Spidey senses say they've moved the oring outboard tho for this reason.
Seems a strange choice if not.

Might not be so complicated. On an inset head, there is nowhere else to put it.

I would think an inset head would make it easier to place an o-ring closer to the bore. may have to rethink my own plans..

Can this kit still be installed on Rotary with Auto lube?

You have to work pretty hard to get a leak from an inset head, so the o-ring pretty much has to be mitigating potential leaks at the studs.

Last time I tore a vmc gasket, I considered just using some copper coat rather than waiting for a new gasket in the mail. Seems like it's not really necessary.

The BGM 177 is an inset head and everything else seems horribly designed once you've run one. Perfect centering every time, head leaks are a thing of the past, and you can dial in your squish exactly where you want it without compromise.

FMP continued his VMC244 videos this week.

And SIP have a build video for an EGIG 407 which I love for reasons far beyond just the size queen aspect of it:
- They show pressure testing
- They are straight up about how much parts modification was required
- They couldn't get it to start on the first attempt

Make sure you check these out thoroughly before fitting.
They've been having quality issues over on GSF

https://www.germanscooterforum.de/topic/432162-vmc-crono-187ccm-die-neue-alternative/page/36/#comments

That's pretty poor quality control, for sure. You'd know it was there with a pressure test, but good luck finding that one into the cylinder stud hole.

I've been waiting on the second batch of cylinders to come out to see if they have revised the castings a bit. Seems like they have.
I've gone over the cylinder many time and it looks great. Excellent quality. Collecting parts to get this build going.

I love me some new shiny parts!!!!!

Well, here's some more shiny for you.

Is there room for a CHT plug sensor? It was pretty tricky on the Quattrini to grind a little flat area off to the side of the plug, as the mating surface for the plug is set down into the casting a little.

I think it might be pretty tough but not impossible. There is good room in between the radial fins that could work. The trick would be getting a tool in there to work. You'd need like a dental drill attachment to a dremel. An under plug tach sensor is no issue.

droooool

FMP put the VMC244 on the dyno with a 62mm bell crank and two different box exhausts.

32-33 HP. 38nM of torque

Impressive.

The VMC kit looks slick.

But still not super convinced by 244cc kits.

Maybe riding the Quattrini for a few test runs might change my mind, but I'm not super optimistic it's more fun than my old malossi 221.

All the 244 kits just need some careful tuning. As they come out the box, they are touring kits.

I thought the VMC had always been positioned as a touring kit. The Quattrini less so, but you run them for the torque more than the HP, IMO.

Neither are for me but both are made for box exhausts. Some careful tuning could make them run much higher HP, with an expansion but with the long rod and stroke, the rpm will need to be considered.

It's interesting that the VMC 252 dyno (at the bottom) goes to 8500 before dropping off, on the SCK Quattrini 252 dyno it runs on to 10,000. That's with the WR1/BB2 on the VMC, and the Polini box on the Quattrini. Not sure if they decided to back off once it reached 8500?

Also interesting, and probably confirms the touring slant of these cylinders, is the jetting shown on the VMC (not shown on the Quattrini). It's a PHBH 30, with 135-138 main, AS266, 60 idle and X2 needle. Fairly close to what I have on mine, I know Jack and 108 expected it to need more.

There's a recent thread here somewhere where most contributors are agreeing that the 150-based cylinders were better than the 200's because you'd get more choice with more punch per cc. So perhaps the market for a peaky 200-based cylinder is pretty small.

Another thing that I had suspected for some time but only recently confirmed, is the dyno numbers published by the Germans (among others). I think it was David Bristow in a facebook group who mentioned this. He says in the UK you never, ever see the same high dyno numbers as the Germans get, and the reason is the Germans use the P4 dyno. Not sure what the UK preference is however.
David Bristow runs Team Hornet in the BSSO.

Edit: found the conversation

Yeah, I'd imagine a bigger main jet, but the larger atomiser and lower clip position could offset that (but the large pilot suggests the clip is nearer the top).

For a first attempt I'd still do 55, AS266, x2 clip 2, 145 main.

But I'd also try the VMC dyno settings and see what that feels like.

Yeah heard that too about other dynos in Europe vs UK

M244 is on a pwk. Written at the bottom. Main jet still only 142. If tuned with a fat expansion, I'm really sure the main jet would end up more like 185.

The shape of the curve. Where it peaks early with so much over run, is a sure indicator there is way more power in it with increased port timing.

I think Ginch is referring to the PHBH30 on the VMC 244 which sounds ok though.

60
AS266
X2 needle 2nd clip
138main

It's give or take a little what I'd try out.

Ok. That makes sense. So it is! Must be blinder than I thought.

They did test other exhausts, I think this is still with basically stock porting, later he adjusts. Anyway even with the Posch Performance Nessie the jetting is not that big at 142 - 145!

https://en.blog.scooter-center.com/alex-builds-a-quattrini-252ccm-vespa-motor-2-quattrini-m244-king-shaft-of-the-super-tourer/

Can really see the science in action with the Nessie. It's trying to overcome the low port timing but just can't pull the curve up. With such low timing the fat pipe resonance doesn't work. An hours work with a Dremel and the story will change completely.

Yeah I have to agree here.
I've been slowly raising and widening my exhaust port 0.5 at a time.
Being careful not to loose that all important low down torque.
Out of the box the MHR187 was around 181. I'm currently at 187ish and the rev on now is superb.
It's lost that torque hump where it would peak than quickly drop off. Now the spread of power is wider through that area happy to sit in the higher revs without feeling like it's in self destruct!

I'm looking at that chart and 6000 rpm peak and think it would be great for touring setup at 60mph on my scoot.

So is that mean the P4 dyno is similar to what the power measurement standard of the popular motorcycle manufacturers if it measures the "crankshaft bhp"? Based on popular beliefs, I heard that vehicle manufactures measure the crankshaft power.. so which one is close enough to the real world/road power feel?

Looking again for this cylinder and a crank to go with it...

Do people on this forum have experience on what to consider when fitting one?

Would this crank be good to go with VMC 244 on VR-One cases?
https://www.sip-scootershop.com/en/product/bell-shaped-crankshaft-sip-performance-uncle-tom-for-vespa-200-rally-vse1t-33997-p200e-px200-e-lusso-my-cosa_45022700

Currently I'm running this with Malossi Sport cylinder:
https://www.sip-scootershop.com/en/product/bell-shaped-crankshaft-sip-premium-uncle-tom-for-vespa-200-rally-vse1t-33997-p200e-px200-e-lusso-my-cosa_45022500

Was also thinking of swapping only the conrod to a longer one, but the rod alone is over 200eur.

VMC suggests a 60mm crank with a 126mm/127mm rod. A 62mm will require packers for the kit. Uncle Tom (SIP / Primatist) cranks are TOP quality...