Modern Vespa

Hey everyone,

Chris and I put a Pinasco 177c two port kit on his 1964 Allstate (Rocket).

All went swimmingly until after about 5 minutes of running it started to make a pinging sound and stopped running. No Bueno....

So we took the cylinder off and the piston was super tight in the conrod. It's like the wristpin froze up.

We ordered a wrist pin removal tool because it was that tight - the piston wouldn't wobble back and forth on the rod.

Upon pulling the pin out there is scoring inside the brass bushing, on the wrist pin, AND also on the outside of the connection to the piston! WTF???

So now we're sitting here scratching our heads....How did this happen? How to rectify the situation? What the hell?

It literally doesn't have 5 minutes on it, and it sounded great when it was running, until it tightened up....

Does anybody have any ideas? How it happened, and where to go from here?

Thank you!

does that engine/crank/rod use a bronze bushing at the small end or a needle bearing?

Yes

EDIT - A bushing....

Bronze bushing, which would normally be OK, but not this one any more.

How did it happen? lack of lubrication. There is a reason why they went away from the bushing to a needle bearing. Now time to go out and purchase and decent crankshaft.

FYI: i do have a few really nice Pinasco units sitting on the shelf. If interested, hit me up.

Balls.

Sorry to see that. :-/

We squirted 2t oil in the bushing and on the wrist pin. Maybe I needed to put grease? I cannot recall what I lubed up B-62 when installing the kit a few months back. Hmmmm. It looks like there will be two engine rebuilds going on now. the 64 Allstate and a 62 Allstate. We'll know more Tuesday afternoon when we get together to split the cases. Then we'll be contacting you. Thanks!

Amazing how quick that happened. Properly disappointing. Good news is the 2 port kit has 3 ports.
Pin was just tight. If the bushing was more worn it would have been ok.

That bronze is hard all the way through and not just on the surface. Would it not be worth a try to ream out the bushing to take a needle bearing? What you got to lose? Measure a P crank to get the size. Re-use the damaged piston. It might not last forever but would go more than a while. Would give you time to maybe sort P electrics and big taper too.

Sometimes, you just get unlucky.

How bad is the scoring on the bushing in the crank? could it be sanded down with a bit of emery paper and then re-use the old wrist pin in the new piston, albeit with a bit of side-to-side play between the circlips? (Note: this may be a Bad Idea, but I still had it)

Can you get detailed (.01 mm) measurements of the comparative sizes of the two pins? They should be the same, as I ran that same Pinasco 177 with a bushing in my VBB for some years without issue on the stock crank.

Would the connecting rod be hardened to be able to use a bearing? With a bushing the rod end isn't a wear surface with a bearing it is a wear surface.

Could that mess be cleaned up with some 800 or 1200 grit sand paper and reassembled? Guessing cleaning up that bushing will increase the tolerance a bit to help with the tight fit. Might take a little off the pin also.

the pin can be cleaned up, no problem. but there is really no reason to keep that old crankshaft with the brass bushing. again, there is a reason why they went away from it. for not a lot of money, a state-of-the-art crankshaft with a proper needle bearing can be had.

Thank you everyone for your feedback and questions.

Chris and I talked yesterday about the plan to move forward - fix or replace.

We both knew that strapping 177 kits on these machines was going to stress the lower ends (that have never been opened). We both knew we'd be opening up the cases and refreshing the whole shabang at some point soon, just not this soon.

Actually, I was planning on splitting the cases on B-62 in the coming weeks.

Which brings us back to Rocket. We both would rather update and replace than "make it work". The energy and effort to replace vs fix is probably less, and the result will outlive both of us.

So the decision we've made is to rebuild both engines, put in quality parts, and enjoy the winter projects. Coffee, tunes, Robot vids, BSing in the garage, scooter runs into town for burritos, donuts, coffee, ocean views, etc...

We're thinking of doing both simultaneously, but we'll see how it all plays out. Since both scooters are in my garage, I'll start and Chris will come over when he can.

Wooohooo - this should be fun! 60/8 club - here we come!

oh boy! Lets do this!

Are you going to cut in the boost ports since they'll be apart?

We weren't planning on it, but definitely opening up the intake to match the carb box.

Boost port already in through the piston.

Very sensible ignoring our bodgery.

Opening the intake: Would that involve longer inlet timing, like your now usual procedure?

When buying a crank, a 60mm would go better. The P taper has to be a consideration too.

Quite possibly. Hmmm, We'll have to look into that. I'm fine with the power where it was at - but maybe changing the clutch gear to a 22t, like you suggested. Hmmmm....