Modern Vespa

I've put my SS180 motor together with new bearings and new seals. The old crank shaft that was in it was toast. The threads and bearing seats were thrashed. So, I found an original one that looks to be in great shape.

There is problem. When the flywheel and flywheel hub are tightened down on the crankshaft, it will turn freely about half way through the revolution and then the fly wheel rubs badly on the top edge of the aluminum motor case. To me, it appears the crank is not straight. There are no binding issues with the cylinder head and piston.

The SS180 flywheel is two parts, a flywheel and a steel hub bolted in the center of the flywheel. If I remove the flywheel from the steel hub leaving the steel hub in place and rotate it with a ratchet, I can see that the hub oscillates irregularly instead of spinning straight. I have another flywheel and tried it and it's the same problem

Is this an indication that this crankshaft is bent and a serious issue?

My GS160 flywheel is not like this at all. It spins straight, nice and smooth.

The last thing I want to do is get it all done, start it and watch it all get chewed to oblivion before my eyes.

If anyone has any thoughts, I'd appreciate it.

Sounds like it is bent or the face the flywheel bolts to is off. Guessing bent as it had to of worked at some point. Try this search has a few videos that should help get you pointed in the correct direction.

https://www.google.com/search?q=vespa%20checking%20crankshaft%20run%20out&ie=utf-8&oe=utf-8&client=firefox-b-1-m#sbfbu=1&pi=vespa%20checking%20crankshaft%20run%20out

Thank you for the link with the information. Unfortunately, I don't have the equipment or expertise available to do something like that. I'm starting to think that the crank I have is not in-line. I bought it from Peter in Denmark, who is very reliable, but I have a suspicion that the local mechanic who has built my engine "installed" it using a mallet instead of a proper puller, but I can't be sure.

These kinds of things have a bright side. Now I will order a new crank and the right tools from SIP to split the cases, remove the crank, re-install the new one, and learn from it. Next month I have a month off work to do it.

take it to someone with a lathe and have them chuck it up with a dial indicator; they can measure the run-out for you for probably a drink or something. i suspect it is out of true.

I’ll try to find a machine shop to do something with it and keep it as a spare. It’s frustrating when I pay someone I believe to be competent and this happens. Now I have to open the thing up again. I should have just done it myself. It’s getting to a point where I’m not willing to let anyone touch it now as I slowly begin to figure out how to do the things I wasn’t capable of before.

There’s a lot of things that I won’t let people touch. I find it better to do it myself for the same reasons. There’s been to many times, I’ve run out of the tools to continue troubleshooting using the tools that I had. Took my car to a garage, to have them replace good parts until they figure out what is wrong and charge a premium for parts and labor. Mechanic tried charging me for hundreds of dollars in parts, I told him those parts were all good I tested them and told you that it’s on the work order. It’s the broken wire that you found that was the issue.

Well, I've taken the jump and taken my newly built SS180 engine all apart after my hesitancy in the build quality. I have found some issues. The cir-clips for the clutch side bearing and the piston grudeon pin were in backwards (round edge out) and the crankshaft was out of alignment as I suspected causing it to hang up at one point each revolution when the flywheel was turned by hand. He simply said, "It's fine. It will wear in." It was either ok, and he hammered it in and fucked it up, or it was out of balance from the start, and he failed to have it balanced. I had advised him to have it balanced. Either way, it had no chance of success after I took the engine home.

Thanks to SIP for helping me get the proper tools (and a sweet new crank) to split the engine and go from there.

It's a shame because I was a long-time customer. Too many niggling issues to remain dependent on others. New tools and more independence is the order of the day.

I will post some photos later.

All of this makes me wonder now how my GS and V90 are. They seem fine, so I won't go into paranoia mode.

From now on, it's me myself and I who will deal with anything, and you guys, of course.

Anyway, whatever.

Sorry for the bad news with your mechanic. Looking forward to watching the work though, so yes... please post pics as you go!