Modern Vespa

Hello all,

Its been a long time since I posted on this forum. Its a good thing cause things are going good. I still read lots of the postings here.

In the summer I did the jet swap for the carburator on my 2010 LX 150 I notice the differance right away. Started very fast all the time.

Now that it has gotten colder outside. I am in Toronto Canada. I notice that when you start it now. It seams to stall after 10 seconds and I have to restart. It does start. Unless I add gas it will stall again. Once the scooter is warm there is no problem.

Now is it the idle that needs adjusting?? Or it the air/fuel mixture that needs adjusting? Adjusting idle is the screw on top of the carburator. That I figured out. Now the air fuel mixture is on the side of the carburator. Do you turn it counter clockwise to increase or clock wise to increase?

Thank you for your time
Edward

You said that once it is warmed up there is no problem therefore in my opinion the air screw needs no adjustment.

For what it is worth I have noticed that on my GT200 I need to adjust the idle up when the weather gets cold and adjust the idle down when the weather is hot. YMMV

I'd agree with Hachi, if its fine once its warm your mixture isn't the issue. Turn the idle up a small bit for the colder weather, I had to do the same thing with my Enfield and my Triumph, carbs can't compensate for the cold like an injection system can.

Mind you, being in Burlington, I'm much further south than you are..... several kilometers maybe!

Carburetors like a little throttle when cold starting, and many folks don't even realize that the LX has a carb heater.

Best procedure for cold starts in cold weather: turn the key to the run position, wait 20-30 seconds for the carb heater to do its thing, twist the throttle quickly once or twice to squirt some raw fuel into the carb barrel via the accelerator pump, twist and hold the throttle about 1/4 of the way open as you hit the starter button.

Mine starts immediately every time this way.

Thank you guys for your help. I will adjust idle today.

Hmmm

My LXV is just backwards. When it's cold out it'll start right up and idle. When it's warm out I have to give it some throttle.

The theory behind cold starting (and cold running until warmup) comes down to this: When an engine is cold -- even if the air/fuel mixture is correct for warmed-up running -- the mixture has to travel down a cold carb throat and manifold and into a cold cylinder. Along the way, a lot of the fuel condenses out of the vaporized mix, leaving what is in the combustion chamber too lean to fire unless the mixture is made extra rich for starting.

A fuel-injected engine compensates for this automatically, but this is what traditional chokes and the enriching jets on carbed scooters are all about... providing a richer mixture for starting and cold running. The carb heater helps to keep so much fuel from condensing out, and the squirt or two from the accelerator pump allows a bit more fuel to reach the combustion chamber.

+1, yup, needs a squirt of fuel to get started in that weather.

I'll have to try waiting a little longer before I crank it over and see what that does.

We have to increase idle speed just a bit during winter months.
I have never heard of a carb heater. Sounds pretty nifty. Any chance Piaggio put them on the '07 BV250s?

The carb heater is just a section of resistive cable strapped alongside the carb. See the image from the parts manual below. It's #6 on the diagram.

Don't know which models have it.

Page 80 of 320 in the 2006 BV 250 workshop manual (as found elsewhere on the MV site), mentions and shows a schematic with a carb heater. Makes sense that if they put it on a 150 that they would put it on the 250. I'm delighted to learn about this as I am 200 km north of Toronto and have noticed that as the weather has chilled, my scoot has been slightly reluctant to start. This will help.

Thanks Silver Streak. Great tip