Modern Vespa

This summer, while in Sicily, I decided it was time to buy a bike to leave there. I picked up a 1979 P150X. On my test rides, it rode fine but I was in a town that was flat. Brought it back to the house, and come to find out it doesn't like going uphill, especially from a stop. This is a problem considering Catania lies on Mt. Etna!

Here is a video of what was going on: ~ 40 secs I am showing that the bike will make it uphill if its already in motion i.e. no stopping but I remember that it wanted to die near the top and required a lot of feathering not to die. ~1:25 I show that from a stop the bike will not do the hill at all.

Excuse the clothes and look please, I picked up the bike 2 days before I left and had worked on it for ~6 hrs under the Sicilian sun, late July. No shade, no work clothes, and all I had was a socket and wrench set, incomplete and 2 screwdrivers It was like being on a deserted island. Total rush to get the lay of the land to figure out what I need to get for next summer/best ask for help.

Now here's what I know of the bike. Its a 1979 P150X with a Polini 177, SI 24/24, and "P200 gears". Air filter with no drilled holes. In the video it has a SITO exhaust (not the SITO+, it looks exactly like a stock exhaust with no expansion into the box). After the fact, I believe it doesn't have the stock engine in it since there was a Ducati CDI and I believe it should be points. Not sure. I didn't grab the engine number. The carb is set with 55/160, 160/BE3/110.

I cleaned the carb with carb clean and compressed air. Under the filter I had found paint chips. Found paint chips in the tank too. Drained and cleaned, filled with new premix. Adjusted A/F mix screw. Adjusted clutch. Turned the engine over while observing the rotary pad. Made a video (see below). Boston scooter people told me it looked good. Nevertheless, the problem remained.

A Polini expansion pipe and 115 MJ came with the bike. I put both on and re-did my test. This time I could start from a stop and go uphill but it took A LOT of feathering to make it happen. The engine didn't feel too healthy while I was doing it. Like I could keep it going but it felt so weak and wanting to die compared to my stock Stella going up worst hills.

Turning the engine, observing rotary pad: Proof it runs on flats: Assorted pics, maybe eagle eyes can spot a clue: https://app.box.com/s/ga2pywnj9verz4la7o4s61ikwovnov6q

So basically I'm just looking for ideas as to what could be wrong so I can prepare myself with tools/parts for when I return next summer.

Thanks, Alex

I'll throw a WAG and say clutch is smoked or getting there or maybe adjusted wrong/worn.

I'd start there in that it seems to start easy and idle well and doesn't seem too chonky when revved

Not sure as he said the bike has difficulty to climb even from speed. Probably a combination of worn clutch, transmission, cylinder… Best solution would be to split the cases and check/rebuilt

Before splitting cases, start with the basics. Do a compression check to see how your rings are holding up and if possibly your head leaks, maybe a pressure test on your case and for sure verify your timing is on spec. The rest of your jetting? What is your plug color after riding around on the level?

As far as your clutch goes, unless you are trying to start uphill in second gear, it seems like it is holding on OK but your motor is just giving up w/ little torque to contribute. Maybe the 24 carb is too big at low RPMs for this setup, like it's loading up at low rpms when you try to start on a minor hill.

I'll take "90% of all carb problems are electrical" for $500 Alex.

Sounds like the ignition is too weak to fire under heavy load. I'd focus on the sparkplug, plug wire and CDI.

Thanks guys, there seems to be a common theme. When I was in Italy, I spoke to Italians about the problem. Then local Boston people. Now you guys.

Looks like it could be:

1. Clutch (you guys and Boston people)
2. Compression (you guys and Boston people)
3. Gears (Boston people and Italians)
4. Mixture (Italians)
5. Electrical (you guys)

This really helps a lot. Prior to this post I already acquired cheapo Indian 21 and 23 tooth full clutches for diagnostic purposes, 20/20 carb (I'm just more comfortable with this carb since the Stella has one), drilled air filter, new fuel line, and a fast flow tap. May have gone a little overboard. I also plan on putting on the polini box exhaust on it.

Greasy, clutch was a little strange at first. If I remember right it would grab much closer to the handle bar than my Stella and I wasn't used to it. I did adjust it like my Stella. One of the photos has a picture of the grab point.

Colin, at the moment I'm working with hand tools and I lost my work space. If the cases have to be split, to a mechanic she goes.

Voodoo, I'm planning on bringing my compression tester. I need to build a leak down still. Looks like I'll be bringing my timing light as well. Jetting is on a 24/24 carb, non drilled AF 55/160 160/BE3/110 with essentially stock exhaust. Im planning on bringing my jets up to 125. I did not get a chance to look at the plug. It sure does feel like going up in 2nd but I'm sure I'm in first lol

Kowalski, I was very worried about electrical when I thought I had a condenser but since its CDI, that will be easy. Plug is brand new, so ill check wire and CDI.

Thanks for all the feedback guys!

Check your compression too. That engine sounds sluggish.

Yes I will be bringing my tester. If its got bad compression, best case scenario is ring swap, worst case is cyl swap?

Correct answer: bad rotary valve!

Good thing there are mechanics here that can weld em up. Got it fixed and runs right as rain now