Modern Vespa

My experience with the pinasco 177 2 Port is it runs hot. I'm running a 24/24 and was really surprised how high of a main jet I had to go before it would splitter WOT I'm 3rd. (It's a three speed).

After a couple of soft seizes at 60+mph, I decided to install a CHT gauge. Best decision I could've made.

Now I can run all day long at WOT and the temp has only once went up to 302F. Mostly it stays around 285F. This is along the coast, so humid and cool.

Here is a record of my jetting. I finally got smart and started keeping records on my phone...

Scott - that's awesome info/deets.
Do you recall what size you drilled your float bowl passage out to?

My Polini iron was a hard seize at 311°.
SIP CHT recorded it seizing there twice.

2.3mm

Is the seize connected to the noise that disappeared 5 mins beforehand? Sort of like Chandlers rogue washer.

Given that the kickstart is stuck, it certainly could be.

Only time and an 11mm socket will tell for sure.

Well… I didn't expect that.

Gracious.
Neither did we.

No fuel in the oil. Piston looks good to me.
Everything else looks OK. Stand works awesomely.

I can't speak for everyone here, but I generally prefer my bearings to be a little more ballsy than that.

Any suggestions for the best way to remove in situ?

Ideally, a bearing extractor, followed by a gear puller. Anything that doesn't transfer the pulling force past the shaft will be fine.

as in leave the crank in the cases?

no. no. no, no, no, no.

remove crank, do both bearings. both seals. you're this far in, it'd be false economy not to.

also, if you don't know the provenance of the crank... I'd be throwing a hairy eyeball at that too.

New crank and both bearings went in on the rebuild.

Well might as well listen to Greasy. I think I have everything here anyway.

So it was lean after all … by a few ball bearings!

Where did they end up?

Piston looks great. It wasn't your jetting.

remember, it's not repair; it's an opportunity to upgrade!

all kidding aside, it sounds like your crank is okay to go another round. I'd just knock bearings on, slip some seals in and party.

All the bearings are in the race. Just friendlier with each other.

Speaking of upgrades. While it's out what do I need to change from the early small bushing thin clutch to the later type besides the cover spacer and a clutch?

Edit: Seriously!?! Everything but a fly side seal.

That is unexpected. My question would be how/why that would happen. Bearings and crank being new…and the noise you were getting after rebuild. I listened to your video and it sounded like piston slap. But it's hard to tell from a video sometimes.

The remains of the bearing cage was scraping away the metal on the seal. Defective bearings happen.

so where did the missing balls go?????

They are all there. The cage snapped and all the balls are close or touching each other. Really jammed together. It's a keeper

So got things buttoned up and it started on the third kick. Left the choke too long and flooded it. Went to restart and it spins so easily, like there is no compression. Won't start. Jiminy Crickets, this engine is cursed.

Rings and piston look good. Guess it's really time to build a pressure tester.

So am I right in thinking if I rolled a crank or flyside seal that this would contribute to my current situation?

Bought this in Aug. 2019. I'd really like to ride it, not constantly be chasing this bullshit.

Don't assume the worst. Sounds like maybe the clutch is too tight. Try loosening the adjuster.

Thanks SoCal. I need some hope today.

Check you spark plug is properly torqued.

No compression == flywheel spins without resistance.

Over tight clutch == no resistance, but flywheel doesn't soon.

I'm Team Clutch on this one.

So I've disconnected the clutch cable, no change.
I can spin the flywheel like dialing a rotary phone. Get hardly any pressure at the spark plug hole.

Flywheel spins with the kick start. Going to pull the clutch cover next as I did change clutches during this build.

I had the head off, piston looks fine. Pulled exhaust to peek at the rings. Weird

If the cylinder walls aren't scored, then something is jacked up with the rings. Only way to know for sure is to pull the cylinder.

Post up some pictures. They help a lot.

Will do

Cylinder looks fine to me. Rings were tight in the grooves and did not protrude from grooves at all. Since the cylinder kit came with the parts I now call a scooter I don't know their history other than it all looked new at the time. So new rings on the way.

It might be a belt and suspenders kind of thinking, but since you're replacing the rings you could hone the cylinder also. I've done this a few times when reusing okay looking original cylinders on a rebuild -- when you want cross hatching on the cyl walls so the rings seat properly. I can't see the cyl wall markings too clearly in the pics.

Do those ports need chamfering? They look awfully sharp in that picture.

Past that...I don't see anything obvious to point me in a particular direction.

So stuck rings. How does the piston look? Doesn't even look like it seized.

This has to be one of the weirdest cases of engine gremlins yet.

First the cage of a bearing lets loose. How often does that happen?

Then rings just get "stuck" for no apparent reason?

Maybe sprinkle some holy water on it next time before you fire it up.

I could see a tiny piece of bearing cage shrapnel getting stuck in a ring.

Past that, ghosts.

Yeah maybe. He said both rings were tight in the grooves. What are the odds of that? If a piece of shrapnel got in there, you'd think you'd at least see some damage.

When the rings broke on the Polini kit, the cylinder was fine, but the broken rings got stuck in the distorted lands. When my Stella crank gave out, the cylinder showed seize marks. Maybe a crank/bearing seize can also result in piston damage.

Definitely strange. I think that aftermarket parts don't always play nicely with the old team. With high performance builds, it can push the limits of the design. But in milder builds maybe more related to small figment issues.

Or ghosts. I have chased many.

I agree, but don't really have a better theory unless the rings were always right at the edge of too tight in the lands. So the mystery of what caused them to go from "not too tight" to "too tight" remains.

Grumpnut, can you share a picture or two of the piston? Any visible marking on it? Close up of the ring lands if you can get them.

Pulled the piston this morning. Tiny bits of crap in with the rings which are tight in the grooves to begin with. New piston from SM on the way.

The top of that piston looks like the lunar surface. Looks like the lands got beat up a little. Maybe debris from the bearing got in there. Either way, rings sticking in the grooves would give you little or no compression. A strange set of failures to be sure, but not your fault if that makes you feel any better.