Modern Vespa

I just joined the board and I'm not sure if a 24-year-old scooter should be in Modern or not-so-modern forum, so I'll start here I have been working on, and rebuilding my vehicles including engines for decades... everything from B&S lawnmowers to 70's Mercedes diesels to a 600 hp Mopar big-block. But the current project has me puzzled.

This scooter belonged to my brother and he recently gave it to me. It had been parked near the seaside in Crete (think salt air) for at least six years so the corrosion is extensive. I wanted a project so I've spent the last several weeks de-rusting, priming, painting, replacing many parts including most of the fuel lines, and drilling out fasteners that were rusted solid to their clip-nuts. The wiring harness had cracks in the insulation up behind the instrument cluster, and the corrosion had caused EVERY wire to break there as well as the flexible PC board copper traces to basically disappear. To make a long story short, I fixed or replaced it all... except it will not start! It was "running when parked"...

I'm here in Crete with limited hand tools and no scooter mechanics I'd trust that are closer than an hour drive (minimum). There is spark and the plug gets wet. Bottom line is, the compression feels very weak, and there is not much vacuum either. It won't blow my thumb away from the plug hole. I took the carb apart and made sure all the passages were clear with carb cleaner and the float/needle/seat works. Reeds appear to be sealing properly.

The interesting thing is that if I shoot a little carb cleaner into the intake, it fires immediately with a big cloud of blue smoke (oil from previous start attempts burning off?) and also revs quite high despite the throttle being closed. But it won't fire even once on gas/oil...

My current working diagnosis is stuck/broken rings, or maybe even a hole in the piston top. I did originally turn it over with the kick starter before attempting to use the electric starter and nothing felt stuck or binding.

Other than a weed-whacker engine years ago, I have no experience with two-stroke engines so any help greatly appreciated! Thanks.

ps Is it possible to change the piston/cylinder without disassembling the bike?

Sounds like a set of rings, at the minimum, are needed. It just doesn't have enough compression. Compared to the other things you've worked on, this should be easy for you, especially if all you need is rings.
Four bolts on the head, pull it off, pull the jug off, install new rings and a new base gasket, jug back on, new head gasket and head.
As far as doing it without removing the motor, can you get the head off, and is there enough room to pull the cylinder if you do?

If not, you can jack the bike up in front of the engine, remove the bolt holding the engine, remove the shock at the engine, and push the engine back, probably far enough to put on a new top end.

Thanks for the reply. It looks like the head bolts should be accessible from the front (possibly unbolting the coil)?

One more thing I want to try before disassembly - spray some gas into the intake and see if it lights off like the volatile carb cleaner does. If it starts that way then the problem is still in the carb.

If it's just stuck rings, I'm hoping the rings will free up if I can get it running. I know, a long shot, but before I spend the $ and effort on a new top end it's worth a try

Remember the old "Bon Ami down the carb"? No, I'm not going to try that

Update: I put a couple of ounces of gas in a clean spray bottle... cranked while misting it into the air intake opening in the frame - and it fired right up! The RPM also climbed way up again despite the closed throttle, and a huge cloud of whitish/blue smelly oil smoke again, so I shut the key off.

Thinking about stuck rings... but doesn't the carb still have to be the problem if it'll run on gasoline spray but not from gas in the carb?

It's alive!

The problem wasn't actually the carb, but the control cable going to it. The sheath had slipped out of its socket at the splitter end, when I was moving many parts and hoses around, and was holding the throttle 3/4 open at idle (and beyond wide-open at full rotation)...

After fixing that, I reinstalled the carb, refilled the fuel bowl and hit the starter... fired right up although the idle was too slow. I cranked in the adjustment knob and now it idles.

It's still blowing a lot of oil smoke out the exhaust at mid- and high rpm though, even after idling for a minute or two and a couple of revs. I need to get it fully warm and run it up (i.e. an "Italian tuneup") and maybe the smoke clears.

Still suspecting ring, piston or bore corrosion... we shall see

I rode it around town today... sometimes the smoke was very light (normal haze), and sometimes it would return with a vengeance.

I also noted that it was hard to start when hot. And that the plug is black.

What this tells me is that the automatic choke may not be functioning (it defaults to rich, correct?) so it's time to check that out. Otherwise I think it's time for rings...

edit: Choke measures the correct 35 ohms, 12 volts measured at both pins with key on. Tomorrow I'll start it and make sure one of them goes to ground so the choke will heat.

My favorite Scooter! Any updates?

No, I'm back in the US until late June but I'll start tinkering with it again this summer!

Awesome! Where In the US do you live? I'm Currently in Florida. I seem to be the only person with the same scooter. Actually, 3 of them!😁

I'm in south central Missouri... but the scooter is in Crete

Back in Crete. The neighbor who kept my Typhoon under cover says it started the first few times in the fall/winter but now is completely dead. I suspect the Rube Goldberg mechanism to pump fuel from the front tank is not working, so I put more fresh gas in while I was at it.

It didn't take me long to discover that the battery was not dead, no blown fuses, but that the ignition switch was simply not making contact. Unfortunately the set screw that secures the switch part is rusted in place But I was able to unsnap the outer part which holds the contacts, clean off all the corrosion and snap it back together. The contact "dots" on the wiper were clean. Now it starts (and still smokes) again.

I've had three attempts at ordering a new brake master cylinder. The first was supposed to come from the UK to the US so I could bring it with me. It never showed up so I got a refund. The second I ordered from Germany before coming to Crete, and DHL lost it in the handoff to ACS (local courier). They are still looking so they don't have to give me my 100+ Euro yet. The third, from a different place in Germany, is coming FedEx and allegedly will be delivered tomorrow. We shall see.

So, once I have properly functioning brakes, which should be tomorrow, it's time to resume the search for the excessive oil burning. I do have a new cylinder & piston kit in hand (came last year after I left). I'll take a closer look and see if I can get the old one out without removing the engine.

Also, I bought a Haynes manual this winter, and did some reading at home... then forgot to bring it with me!) Anyway I can't recall if they said to pull or lower the engine first. Guess I'll find out!

OK, master cylinder finally received and installed. Now back to the excessive oil smoke!

As I mentioned, I forgot to pack my Haynes manual... so can someone please explain the oil injection system (I know there's a pump, but how is the oil introduced)?

Since the oil tank is above the engine, is there a way that a leaking seal or diaphragm can allow oil to drip into the engine when it's sitting in storage?

If so, where would it accumulate? In the crankcase, so the incoming fuel/air would also dissolve more oil into the mix?

I am aware of the possibility of transmission oil getting sucked into the engine if the seals are bad. Hoping it's just a broken or stuck oil ring - I would rather replace the piston/cylinder than tear into the engine case...

Local scooter mechanic looked at the Typhoon this evening. He is certain that the problem is accumulated oil/grease in the muffler, and the smoke is coming from there and not the engine itself. I hope he's right. He thinks it will take a long time for all of it to burn off.

As usual a new one seems to be unavailable (and would be quite expensive even if I could buy one). The mechanic's suggestion was to have the muffler cut open, clean it out, burn the oil off the packing with a torch, and weld the case back together. There is a guy in my village that can do it.

As crazy as this might sound,You can throw the whole muffler in a bonfire and it will do the trick. Yes i have tried this method successfully

Remove the muffler and block the end that joins the exhaust with a potato (cut the potato in half and jam it on the muffler end).

Now fill the muffler with Caustic soda to eat away the oil and grease.

Give it a final rinse and then re-assemble.

This is the easy way I used to do way back in the day (Sfera 80).

I live in the village so I can't build a fire and make clouds of smelly smoke. But the use of NaOH sounds like a great idea, thanks!

How concentrated should the solution be (e.g. use liquid drain cleaner as it comes from the bottle)? How long should it soak?

It's been too many years since I last did it - I probably just followed the instructions on the container.
Load up your muffler with the concoction, and give it a bit of a vigorous shake and let it sit for a bit - periodically give it another shake.
Tip it out and repeat with a fresh mixture - you'll note the progress you're making as you see cleaner effluent when you tip it out.
Once you're satisfied - its never going to become super clean - give it a rinse, re-assemble and run the engine to dry out the muffler.

Here I can only get a 60g packet of sodium hydroxide crystals ("Tub.O.Flo" brand). I bought two. There is liquid cleaner but I'd have to drive somewhere to get it.

The packet instructions say to use with 250 ml cold water...that won't fill this big muffler unless there's a lot of stuff inside. Guess I will try one packet first, although warmer water will likely remove more oil...

I had a hard time getting the solution back out... also I ran a garden hose into each end and filled it completely, then tipped and turned the muffler until some fluid came back out. There really wasn't any visible oil and only a few flecks of carbon. Crossing my fingers it was in solution with the lye.

So I got all the water out that I could, then bolted it back on and went for a ride. No smoke, and I flogged it pretty hard. I still suspect the water-logged rock wool is keeping it cool enough not to afterburn in the muffler.

I'll take it for another longer ride once I fix the turn signals (neither rear is lighting up, so the fronts won't flash either). They were working when parked last year

The carburetor usually has a check valve where the hose from the oil pump plugs in. If that's bad, oil will leak into the carb and down into the crankcase when the bike is sitting. You will have the crazy smoke when you start it up, but that usually dissipates after three to five minutes.

Thanks, I'll look for that. How about if it sat since last September? Could be a lot of oil... the tank is pretty good sized!