Modern Vespa

Where can I get that Fisher-Price engine play set? That's exactly what I want.

You check Scooter Mercato? I think they stock it.

I would have sworn there was a 60mm stroke bell crank with a 105mm con rod, but I'm not seeing that now. If bell crank = 110mm con rod, then, yeah, I would KISS and use the 60mm stroke flowed crank. I have the 57mm version in my 177 and I have been favorably impressed.

I thought the same thing, but couldn't find one either. I ran a Worb5 57mm flowed crank in some of my earlier Stella builds and it's a respectable piece of kit. I probably still have it on my shelf, now that I think about it.

Make one. 60mm with 120 rod for the win.

That's kind've going the opposite of KISS. We were looking for a drop-in 60mm crank with a 105 rod, remember?

Any time I'm the Voice of Reason in a tuning conversation, you know things have taken an extreme turn.

A 105 rod on a 60mm crank gives you a 1.75:1 rod/stroke ratio. That's terrible. A ratio of 2:1 is 'ideal', which is what the 120 rod gives with a 60mm stroke crank. A 105 rod on stock 57mm crank is already bad enough and causes too much stress and wear on piston thrust side, in addition to piston speed oscillations that have adverse consequences on charge transfer and combustion process. For fun I like to measure pistons and cylinders, on the 150 engine the piston always goes oval on thrust side, along with stress cracks. This is the consequence of a low rod ratio. The increased stroke is not worth the reduction in reliability.

If you want KISS then stay away from 60mm crank with 105 rod. Get the 57mm cut-back crank. If you want improved reliability then stick a 110 rod (from the 200) with conversion bearing on that 57mm crank. Not difficult for local builders to pull off. Want even better? Put an RD400 115 rod on that crank with some machining and part mixing required.

It gets complicated really fast once you start contemplating. Still, a simple first build is probably the least frustrating path. The good thing is that even mildly tuned builds give enough improvement to put a smile on your face.

Yes to all of this. Starting out, you're still learning how to do the rebuild right to begin with. No need to go crazy when it'll be more expensive if you get it wrong and more likely to blow up with the higher power.

A well-assembled, basic set up upgrades will be enough to get it up on par with a P200 (albeit with a different power curve) and still be a solid daily rider.

Thanks to all.

Chandlerman, yeah we need to meet up at some point. It looks like you have some cool bikes. My working reliable is a KTM 500, so we could go for a ride some time even while my stella sits in pieces. Thanks for the comment about the flowed crank, I hadn't considered that, and I am just using "filter by model" to select parts ... it seems that might not be super reliable, so maybe once I get the full order, I'll ask you to take a look and make sure I am ordering things that look compatible. Of course, if you have any of those special tools that you only need once every 5 years or once in a life, then I would be happy to borrow (eg., bearing pullers, seal pullers, or assembly jig to install new crankshaft and close up cases or whatever)... I'll write you again soon

We should definitely meet up and ride sooner than later. The smallie can pretty well keep up with the KTM, I'd guess, or you could ride another of mine. We can go terrorize the tourists on Broadway. Loud pipes ruin nights, y'know.

For tools, I absolutely have you covered. If you have the engine out of the bike, we can do the engine rebuild in well under a day. I need to replace the clutch side seal in my Stella, so could make it a two-fer, even.

I used to think 200's were the be all and end all because of lack of knowledge and being stuck in the 80's. At one point I reached out to FMP and he said that building a 200 big block wasn't necessary as small block kits had evolved a great deal over the years. Many others have said the same thing.

Ok, thanks to all for the help, especially Chandlerman who is local here... Final decisions look like this:

1) A new flowed 57 mm crank (actually lightly used one) will go in
2) A BGM 177 cylinder kit, decided that, since the cylinder was going to at least need a re-hone and would need a new piston, may as well add some cc's and get a little bit extra power (this will get paired with an existing Polini box exhaust)
3) A full engine rebuild kit for Stella 2T from Scooter Mercato... they put it all together in a convenient kit, comes with main bearings, oil seals, a lot of the wear-out parts that others have mentioned like kickstarter gear, cruciform, etc, new clutch springs and cork plates, and lots of gaskets and orings etc
4) I will do a full re-jetting of the carb with all jets to be optimized

I'll try to remember to post again once all the work is done and stella is running again, but thanks for all of the advice

Just to close the loop. The job is done, and Stella is back in business! Thanks again to Chandlerman, I might have been able to put it all together without his help, but it would have taken WAY longer, and I learned some things I would have never thought of otherwise (like putting sealants on all gaskets to prevent air leaks and actually calculating optimal cylinder spacers based on port heights and piston height, to get squish perfect, etc). I'm just going through jetting now and being OCD, but I am back riding to work and ripping through the town! Thanks to all for the helpful advice.

Glad it worked out. Sounds like a nice combo. You're in good hands with Chandlerman.

On a four-stroke, the compression stroke runs essentially from BDC depending on when the intake valve closes. On a two-stroke, it begins when the piston closes off the ports. How does a longer stroke crank increase this area ?

Be careful slinging around words like "in good hands" when you're talking about me. I don't want people getting unrealistic expectations!

Don't sell yourself short, man. Your hard-won body of experience in the field of "been there, done that, blew it up" uniquely qualifies you to guide rookies past a significant number of scenarios and encourages them to find new and exciting ways to e'splode stuff.

"uniquely qualified...to find new and exciting ways to e'splode stuff" sounds about right for me!

Eley and I actually discussed at length how splode-y he did or didn't want to be, and he said he'd like to avoid splitting the cases for five years, if possible. Plus, he mostly rides within Nashville proper, so we went with limited upgrades: a 57mm flowed crank (I had a very lightly used Worb5 on my shelf that I was happy to move along at a fair price), the BGM177, and Polini Box that he already had.

Per Eley, it's still a little soft at 1/4 throttle before getting on the power, so we need to look at that, but revs nicely and really smooth throughout. I need to drop off some atomizers and and idle jets for him to try out, but it's already solid for around town.

It's peppy, but not so fast you have to be careful when you jump on the power, and should be good for 65 MPH with the stock Stella gearing, not that I'd recommend it until he gets some better tires and shocks.

And better brakes also starts to come to mind