Modern Vespa

Hi all,

Some months back I bought a Piaggio Fly 150 from a guy for 75 bucks. The plates say 2017 so I'm guessing it's been a hot minute since she ran. Went through it, removed and disassembled cleaned and put carb back in. Cranks but no start! Hmmmm... here's what I verified:

1. Fuel flows to the carb
2. There's Spark

That was a month or 2 ago. Last night I took the valve cover off, both valves were really tight, loosened a bit esp the exhaust valve, went back hit the start, this time she starts but on for a half a second, and only when I've sprayed carb fluid directly into carb intake....It's a step in the right direction, but I'm at a loss now. Should I loosen valves a bit more, should I clean carb a 2nd time?

It just seems, that even if gas gets into the combustion chamber it's still not thinking about staying on...any throttle input at that time dows nothing, still dies immediately. Does anyone know the valve specs? Lastly, there's only one air fuel mix screw I turned it 2 out from all in, which is from what I've researched, the appropriate spec.

intake .1 exhaust .15

Worth re-doing if you didn't use those specs, but if you didn't what did you use???

Do you have the original airbox? I see the k&n type filter and it's off--I wonder if it's getting too much air, or it was messed with (jets-wise) to make that filter work. If you can't get it started, I'd revert to standard config, airbox/filter/jets/etc, for troubleshooting. And check compression after that.

Thanks for the reply, ok I def didn't use those specs, so I will redo valves. Airbox was connected (there was no filter element), I disconnected the airbox hose because I cleaned the carburetor, and left the carb intake open because I figured to initially start it, I'd use fluid /carb cleaner... why? do you think having it open is creating a problem? never has been an issue with other scooters I've done that to (to initially fire them up only).

Thx again for your input 👍

You got yourself a real bargain there - at the very least, a highly serviceable bargain. The Fly has the same 2-valve carbureted "LEADER" engine that all the contemporaneous Vespas and Libertys have. There are tons of videos and guides on how to fix them here, on YT, and elsewhere.

Ok! I followed your specs and redid the valve, then I actually put a towel on the intake side of the carb to restrict slightly, fired right up!! YES!!!! Now the question is, jury rig and intake with that cone, or buy a stock airbox (current airbox is missing the cover and element). I've heard these do well with cone intake, what do you guys think?

Next, gotta fix a rear flat, and then see if I can do a test run.

nice, congrats! I know very little about Vespa's so maybe someone else can weigh in on whether or not a non-stock airbox is a good idea. I read somewhere that you can drill a hole in the airbox for higher altitudes (to increase the airflow where the air's less dense) so I figured these things were sensitive to the expected airflow.

Good luck with your next steps.

My 2010 Fly 150 was pretty reliable; it had close to 25K miles on it when I sold it. I would see if you can source an original airbox. It can be modified for a bit better flow, but as you have discovered it runs better with some restriction.

Also be sure to disconnect the evap system hose from the carb and attach a small piece of filter foam over that outlet.

While you have everything apart, check the stator. It's positioned in a place where dirt can get to it and bugger it. At the very least, hit it with some compressed air.

Based on the age, likely need to replace oil and filter, brake fluid, and tires.

Finally - do a full transmission service while it's apart. Belt and rollers should be replaced, check the variator and clutch for wear, clean and scuff the inside of the clutch bell and clutch pads.

Don't mean to threadjack, but quick question: what's the benefit of removing the evap system? Not trying to start an opinion war, but I was planning on leaving mine on my LX150 alone if there wasn't some reason to mess with it.

The biggest issue with the evap system is caused by overfilling the gas tank. Liquid fuel can fill the charcoal evap canister, which subsequently chokes the carb and results in intermittent difficulty starting.

It was put on to these machines to satisfy California emissions at the time, and have proven to be problematic to many riders - myself included.

And it's easy to remedy - simply disconnect the evap line from the Carb and attach a bit of clean filter foam with a ziptie to the outlet on the carb. Literally takes just a few minutes. You can leave everything in place as well.

Search on this site for evap canister, and you'll find several threads detailing which line to disconnect.

Good Luck!

Where did you hear that?

I think it was YouTube or some online articles somewhere. So because I'm missing the airbox cover, I'm gonna jury-rig a cone, and see what happens. If I somehow can't make that work, I'll spring for one on ebay and get a whole new (to me) airbox.

So did my mod...stock intake hose and cone filter (mainly because as I had mentioned, it didn't come w a complete airbox). Cold start is an issue, once I introduce carb fluid or gas down the intake, no problem... so I'm thinking the choke plug may be bad??? I can also try to restrict the cone filter and see if that helps, but my initial feeling is that maybe that choke electric plug isn't working...thoughts? My buddy, big dirtbike guy, suggested I go with bigger jets, because I am now introducing more air... a possibility, have to see if I have jets from other keihins that may fit.

What I would do:

Before anything else, replace the intake manifold. It's in bad condition and is almost certainly allowing in air, causing a lean condition. [edit: airbox hose is also looking pretty shabby.]

Secondly, get a stock airbox. You got the scooter cheap, spend a few bucks here. These were designed with certain parameters and you're way outside. How far? No way to tell. Chasing the imbalance with bigger jets is a needle in a haystack, and even if you get the mix right, it's still too much juice for what the scooter was designed to do.

If these two don't fix it, remove and rebuild the carburetor. There are videos that show how to do this, in real time, and it only takes an hour. Twice that for pausing and getting out the stuck screws. Simple carb, and tbh, replacing anything in there is optional if not tatered. Just take it all apart, clean it really well, and put it back together. Keep the idle screw in the same position and document the position of the mix screw and it should be close enough to go when it's back in.

Sorry been away for a bit on travel. So I removed the carb again and cleaned thoroughly. Ordered the stock airbox (not here yet). So once again as you can see I have my skunkWerks intake

Cold atart still an issue, but with a lil carb cleaner sprayed, it starts fine, idles good and revs no problem. Here's the 100k dollar question: which I um failed to mention before but now that I think of it I should. I used a much weaker battery for all this, since the original (bigger battery) was dead on arrival. I have a cheap china 50cc scooter battery. Could it be that it doesn't have enough cold crank amps to get the scooter going when it cools down, but enough when it's already warm? But then again, when I introduced fuel spray (when cold) the cheapo battery does the trick... I dunno, thoughts? Anyway. I should have the airbox installed mid week, and will report. BTW, there were no cracks going through on that header, just some superficial stuff which I filled as you can see from the pics.

Until someone smarter can weigh in, here's my opinion.

If the battery is healthy enough to start it with starting fluid, it's at least close enough. The starting fluid richens the mixture, which is what you want when the scoot is cold. IMO, you're getting too much air with your rig compared to the more restrictive airbox and denser foam filter, so you're too lean when cold and the starting fluid helps offset that. But: you'll eventually need to get the right battery, so why not spend the $40 now?

All this assumes your choke is functioning correctly as well. Looks like there are threads here that cover how it's supposed to operate, how to test, and how to clean/repair.

All this said, I'm still thinking going OEM for the airbox and related (hose to carb, filter/oil, etc) is going to either get you there or make the path more clear. If I'm off base about this, my apologies for driving your purchases.

It might help to let everyone know how it runs when warm. Sounds like that's OK? Is it actually road-worthy and have you run it once warmed up? I'd also recommend spraying the carb and intake manifold in carb cleaner to see if it affects idle to rule out a vacuum leak somewhere. And not sure what having the valve cover breather open does--it may make sense to put your finger over the tube and see if it affects anything. Doubtful though I'd think.

I'm with you on the battery situation for the most part... I hadn't bought the right battery because I 1st wanted to see if it was worth it, as I didn't know if it ran.

Idles good, so I don't suspect there's any leak anywhere. Also, I um... inexplicably found the airbox cover last night (I could have sworn I didn't get it with one!! Lol... Anyway, canceled my ebay purchase (hopefully), but did order the filter element which gets here tomorrow. I will rig everything up Tuesday and see how it goes. Have not taken her for a ride yet, since the rear tire valve stem is shot. I will next work on removing wheel tire and getting that repaired, after that... mayden ride should it all work out. Will report, and thanks!

You can replace a valve stem without removing the wheel/tire. Someone posted about it on this forum. There are special valve stems for this sort of thing

Landy, yeah the whole base of the stem is cut. I know I have seen some use those vice grips on tire to then reach in and swap out the Valve stem. That'll be next once I get her running right.

So put everything back to stock, airbox/filter element... seems like she did better but still cold start is a no go. I'm thinking it's gotta be that electronic choke. I will test it and potentially replace it maybe even with a manual one assuming I can get to it from below. Will try to see about testing it tonight.

If the auto-choke fails, it fails ON, not OFF.

So that should not be a problem for cold start. However, perhaps it has failed in the ON position for the prior owner and instead of fixing it, they adjusted the mixture to over compensate.

Ride it 5 minutes, get it warmed up. Then try to set the mixture screw so that it is at the highest idle point. Then back off the idle screw, and go back to adjusting the mixture to highest idle, then back off the idle screw, repeat, repeat, until you have it at an idle where the back wheel isn't spinning. Then let the bike cool down. When cool try to start it cold.

Ok, I can try this....

So the mix screw, I basically have turned in all the way and then have done 1.5- 2 turns out. (BTW on the mix screw subject, it has a spring a washer and an O- ring, correct? I ask because I have seen some illustrations that don't show the O ring.

Last night while I had the scooter on (starter fluid) it idles alright, but initially is seems to hunt around for idle it would accelerate idle and then slowly come back down. When u blip throttle it still kinds take a second or two to come back down to idle. Play with the set you suggest.

hunting for idle -> something wrong with the carb or the intake manifold.
1) with the engine running, spray carb cleaner or ether on and around the intake manifold. If idle increases, you have a leak. If no changes, then all good.
2) take the carb apart, clean jets, and reseat the diaphragm using some grease.

Ok, see seemed a lil more compliant this time...was cold and started 1st hit. She died 7 seconds later, and then wasn't wanting to start. Tried 3 times and nada, let her settle 3 mins tried again, and started. Lol!! What the heck!? At this point she died again because the idle screw was set too low, battery was toast. Took a big ol BMW 1200 battery, jury rigged it and went back at it. Started her and was trying to being the idle down to as low as possible (sorry rear wheel still turns no matter what) still has the issue where when you snap the throttle, it takes her a lil bit q or 3 seconds to come back down to idle. Almost sort of got better as enriched the fuel screw... Anyway, then I did as you suggested and sprayed carb cleaner around to see if it would change the idle, and YES, right where the airbox intake hose goes on the carburetor, as you can see it was damaged and I tried to repair w plastiweld. Ok, going to either source that hose or find a similar one at the local autozone. At this point, should I still remove that diaphragm cover and add grease to the edges of the diaphragm to make sure it's seated, or should I wait to source the intake hose given that I 100% know it has a leak?

Thanks again all for the help, I feel like I'm making progress... slow progress, but progress nonetheless!

On a side note I couldn't even focus at work this was eating at me so much! Lol

replace intake manifold first. Very likely this will solve the idle hunting problem, so no need to mess with the carb. Though, if you haven't already, it's useful to clean the jets in the carb.

you can get a new intake manifold from scooterpartsco.com . Make sure you get the correct one. There are two models. https://scooterpartsco.com/fly-150-20052012-c-108_3547/?sort=20a&page=6

Oh I see the issue (perhaps) my intake manifold doesn't have a gasket.