Modern Vespa

If I replaced every part that had a chunk missing out of it...oh, wait...never mind...

Do you have pics of the chunked selector box?

Here ya go

It looks like that missing chunk won't affect the shifting? Not ideal, but I have seen plenty of scooters with no selector box cover at all. A missing chunk still offers much more protection from the elements than no cover at all.

Just sayin, but that selector box could also be welded back up.

I gave up on getting it because I can't turn the engine to shift through the gears because it is locked solid. That's a project for a clear bench after this engine is installed.

Yeah the KR is a great part...

the paw has been reinforced, but not much done on the little arm that interacts with the paw.

the paw is nice and straight and looks like it'll be a lot of kms before it warps...

I had play on my old one where the pin just wears and elongates the hole in the pivot in the mini arm (the area with the grease).

Upgrading the gear selector is a no brainer, especially if youve tuned the bike

It is always nice to go to somewhere where the guy at the counter knows his stuff.

Down to Motorsports, Steve looks at the gear and says "that doesn't look right". We have a new 4th now.

On the selector box, he sold me a new pivot pin and block for the spring.

On the rings - had 'em. But he pointed out there may be no surface sealing area on the LML cases with the Piaggio stock 150 top end, because the ports are so much bigger. I bought an extra base gasket to check. I'm thinking it's unwise to doubt him....

If the ports won't work out, then the 150 will go on the 2nd engine I build, no biggie.

There's a lot of meat on the Stella cases. I've cut BIG ports into them with no issues: BGM 177 with the gates removed, Malossi 166, Polini 177, DR 177 (just kidding...its ports match stock unless you get out your Dremel).

Regardless, you'll be fine!

Yeah his point was the case ports are big already compared with the surface on the bottom of a 150 piaggio cylinder. Pic with base gasket forthcoming when I get home and check!

Worst case is I have to kit it . But this top end will work for one of the engines.

Doh! I was thinking the other way around.

Never having done anything with stock top ends except remove them and eventually find them away, I'm not qualified to have an opinion on that one.

You get 1/3 of the gasket surface near the port to seal, it's narrow…

The cylinder

I honestly think you'd do better with no gasket and motoseal, the sealing face would be wider

That seems like more of a gasket problem. Just needs a gasket that will sral properly.

Is that a Stella base gasket? I've cut my own like others here with a selection of material from Grainger, bought a pack of shim material just can't remember which pack.

perfect question, here it is with a Stella gasket, I think you've nailed it!!

The selector crowd wins, it still won't shift properly. I'm considering just using the 35t 4th because it seems to work with this box, but that may be a mistake.

Ideally, you'd figure out the root cause of what's not working (and share it with us all), but at some point, yeah, if it works, it works so long as you're good with it.

I think I figured it out!!

It's my testing method. If I nudge the drum forward or backwards during my shifts (wheel spinning) along with spinning the engine, it moves through all 4 gears now!

Tell me what you think.

Woohoo!

I think I can explain what's going on, but it'll have to wait until tomorrow morning when I can go validate my theory by playing with a gear stack in a split case on video.

Post it up here!!!

But damn it if I'm not now eyeing those huge ports on this Stella engine and daydreaming on kits a bit. Maybe I will when I modify primaries for the VBB. I had half considered leaving this engine in the px and building a 2 port pinasco for the VBB but now I'm thinking this engine should go to the VBB after all. Time will tell.

So wait a sec...during your first testing when the selector box wouldn't go into 4th gear, it wasn't when the scooter was running and driving?

Nah this is just bench testing, haven't even put the top end on yet! Still have pressure test coming too…

Oh, in that case, then everything sounds just fine. You won't be able to shift into 4th (and probably not 3rd either) just by ratcheting the selector box. The tire must be spinning (even very slowly) while you're shifting the selector box!

I was going to ask if your opening up that cylinder a bit. Not sure how much O-tuning can be done. Like a few others here I've never actually touched, dare I say, a stock cylinder. 😂

This.

I'm going to try to make a video this morning that shows why that's the case, assuming my mental image is correct.

it looks like not much room for intake port enlargement. The exhaust port could be wider but honestly the best o-tune might be a Stella cylinder! I did some sleuthing last night and the px150 ratings I saw were 7.5hp but the Stella clocked in at 10, that's huge. Given the ports layout and the reed valve I tend to believe it.

Having had a stock Stella, I don't

They were designed for reliability, fuel economy, and the ability to be manufactured by a workforce whose quality ethos is best summarized as, "They apparently only made two scooters per week, the first one on Monday morning and the last one on Friday afternoon."

I love the dumb thing, think the natively reed-inducted cases are a dramatic improvement over the rotary, and can definitely blame it for getting me into tuning and wrenching in general, but I just don't buy 10 HP without a fair amount of work.

wow need a Stella cylinder for comparison

it looks significant, the 2 are below. maybe not 10hp

Genuine claimed 8 hp for the Stella, but that was with The. Worst. Exhaust. Ever. Plus a crappy air filter. I think 10 hp with a tuned box exhaust, P200 air filter and suitable rejetting is credible.

No chance you'd get a new piston and use that Malossi 166 jug?

yeah i might. i'm trying to juggle the 3 engine 2 bike circus here, but I haven't looked in the other 2 engines yet because the bench is filled with this one. it's hard to make a plan without knowing what the story is on the other 2. One is the stella. One is a PX125 engine that is locked and appears to have been neglected in some ways (locked up crank, lots of corrosion, chunks from selector box, etc.) The other is a 2 port 125 engine with points flywheel and is more correct for the VBB anyway, it spins freely and looks much cleaner on the outside than the other 2. I've never done the old style engine without 2 part flywheel bearing, seems like a pain but probably NBD. So without getting hundreds of dollars into a plan and then wanting to change it, I think the 150 top end makes sense just to get something into the PX frame that works and take stock of the other engines. The PX engine might be a total loss inside, I'm prepared for the worst based on what I see.

The first thing that came to mind when I saw this was, "can you come over and organize my garage?"
Very well laid out, and you're going to be busy for a while.

small spaces call for good organization!!

I'm now at the point where I don't honestly know off the top of my head how many engines I have. Six or seven. I'd have to go count them to be sure. Four bikes, but that's always subject to change.

I shot some video trying to explain your transmission issues, but none of them worked to my satisfaction. Basically, it's a result of gear ratios and the fact that the gears are locked together by the primary drive, so the axle has to turn for the cruciform to align to the slots in the gears.

Splitting the cases on the older motors is nominally harder than with the two-part bearing, but mostly just needs some heat on the fly side cases so they expand enough to release the bearing. Getting them back together is more of a PITA, though, with competing methods and even a thread on here which got pretty heated in its own right at a couple points. I don't know if they're in the wayback machine or not, but my Stellaspeed posts as I was rebuilding my VBB motor for the first time a comedy gold. I think half the community didn't expect me to survive the experience.

So compared to that, you'll be fine!

Pressure test - reed leaks

https://youtube.com/shorts/jDS3T7Tw988?feature=share

Video 2

https://youtube.com/shorts/qhAo3rm3VdY?feature=share

This joint is hard, I cut a new gasket and no different, I think the joint is leaking under the gasket. Maybe motoseal is called for? Suggestions?

Yeah, that T-shaped joint between the case halves and the reed block is a tough one to get tight. I use a little RTV at the top of the case halves, then again on the entire reed block to case gasket and sealong surface.