Modern Vespa

Hello all,
I've been having problems with my BV when the temperature is below freezing. It becomes very difficult to start and I have to crank the engine for quite a long time.
The colder it gets, the longer it takes to start it.
Any ideas what are the most common causes? Fuel system? Ignition system?

First guess would be your battery. The colder it is, the less juice they provide. It may be on the way out (most likely) or it's not getting charged up enough while riding.

Put it on a charger and crank the engine when it's cold. If it fires right up, replace it.

I have two bv. one is hard to start cold just like you describe. the other will fire right up. i did find its best to crank engine three turns only. then cycle ignition and try again. did try knew battery and that didnt help. wish i knew actual cause. lots of cranking high compression and low oil pressure is hard on crank bearings and piston skirts.

It is a 2016 BV350, a quite recent model.

The engine is cranking well, so I expect your battery is OK.
And you get it started.

How does the engine run after you get it started?
Does it run smoothly or does it have difficulty to pick up power when you turn the throttle, does it seem to lack power until the engine is on temperature?

I have presumed that cold weather reduces the available power from the battery and increases the friction of the fuel pump that pressurizes the injectors - so a bit of extra cranking is simply necessary in cold weather. I sometimes flutter the throttle a bit to get it to catch, though I'm not sure if that actually does anything, as it would with a carburetor.

But by "extra cranking" I mean five seconds' worth or so. Is that what you're seeing?

Froggio, didn't you use to have a Beo 500ie? I read up on your posts on ADVrider when I bought mine. You didn't happen to sell yours to a guy who lives in upstate NY, did you? Because that's where mine came from, and it had been an NYC bike.

I have a 2020 and have a similar issue with temperatures 50 degrees Fahrenheit and below. It Will start but when it's throttled it will die. It has done this since new. It has to idle until it's warm. I seriously doubt it's a battery issue. I've often thought it's the thicker oil. I also am interested in knowing why.

That would really annoy me. The whole point of FI and the O2 (lambda) sensor is to prevent this from happening. These engines have an ambient air sensor in the throttle body, a little grey thing as I recall, that informs the ECU of the air temperature so its density and oxygen content can be considered in the air:fuel ratio. Have you ever checked to see if it's working? I think the dealer's computer can confirm this. I don't have access to the computer but I found a sensor on eBay that cost less than $10 so I swapped it in to confirm it wasn't the source of my problem (warm engine stalling at idle).

I informed the dealer several times when it was under warranty. Nothing was done.

Battery is not the issue. I can see on the dashboard the voltage and I can hear the starter cranking nicely

Once started, everything is fine. Just back to normal.

Thank you, I'll look for one and switch it at the next maintenance which should happen as soon as the weather permits.

Yes, I had a red 500ie with large windscreen that I sold to someone north of the city. A very nice scooter, but like a Ferrari, it made a burning hole in my pocket. I bought a BV and never looked back.
How is yours doing? If it's mine, it has a newish fuel pump and fuel hose recall. Took me 6 hours to get to that pump and back. That scooter is like a Russian doll, body panel after body panel. A headache!

You're chasing a ghost that is more than likely a mapping issue. I have no proof, just suspicious everything else is working fine. Otherwise you'd have an engine light/codes stored.

Also keep in mind the BV has an automatic compression release, and cranking compression is only around 75 lbs. I know this because I checked cranking compression after replacing the top end gaskets on my '13 BV350. Such low cranking compression does not build up the kind of heat needed to immediately light off a cold engine in cold temperatures.

Aha. Mine is blue, and I think always has been, so it probably isn't your old scooter. It had the fuel pump recall long before I got it.

Rather to my surprise, I love my Beo. I got an incredible price on it from a guy who had to sell it quickly before moving to Hawaii, and the previous owner before him had done a lot of work on it. My plan was to fix it up a bit and flip it, but the pandemic set in and I started riding it for my occasional 50 mile RT commutes. Those commutes became more frequent and I stopped thinking about flipping it. That was almost 11,000 miles ago and it has almost 25,000 miles on it now. In fact I rode it in this morning.

Getting to the engine or anything else that isn't under the front panel is a ridiculous exercise in disassembly - I compare it to an armadillo, but a Russian doll is every bit as apt. However, I haven't had to do that very often, and it does get faster each time. I've done all my own work on it so far, so I'm not paying a shop $125 an hour for futzing with a dozen panels. The parts I've needed have been easily found from AF1 or occasional Italian and UK scooter shops online and on eBay, and haven't been too expensive. It's due for a second belt change soon and a valve clearance check under my 2 years of ownership.

I've upgraded headlights to LED, added cheap but wonderful Chinese heated grips and seat pad, a signal beeper, Qi wireless phone mount, replaced the nonfunctional cables that operate the seat and gas lid, replaced the rear and front bearings, tires, brake caliper, and spiffed up a bunch of cosmetic items. I guess I've got less than $1k of nonwear items in it so less than $2k in the scooter overall. It's been a heck of a deal.

That is interesting (and not expected).

I also was thinking of some issue with mixture enrichment when cold (as Juan thinking of the ambient air sensor) because it looks like a not good working choke in old carburetor engines.

But if that were the case it would not run properly once started, not pick up power normally until the engine is warm. Because that faulty sensor would still give faulty readings to the ECU after started.

So I can't think of an explanation so far.

Can you explain that about the automatic compression release? New to me.
And why would the engine need heat to light off a cold engine? It is not a diesel engine.

The compression release is mechanical. It bolts to the cam gear and has a spring that keeps the compression release weight in the retracted position. In that retracted position it causes some of the compression pressure to be bled off by momentarily "bumping" a valve open part way through the compression stroke. Once the engine fires and speeds up past cranking speed, centrifugal force overcomes the spring and the compression release rotates to the running position, which means it no longer releases any compression.

Both gasoline and Diesel engines need the heat of compression to run. In gas engines the compression stroke squeezes the air in the combustion chamber causing it to heat up, but not enough to cause the fuel to spontaneously combust. The spark from the spark plug trips it over the edge, and combustion occurs. If you want to see how important compression is to making a gasoline engine run, take away compression and watch what happens. Obviously it won't run.

Engines with low compression can be more difficult to get started in cold weather because low compression pressures don't generate a lot of heat. With the BV 350 generating about 75 psi of compression during cranking, that's a fairly low amount. Conversely I think the compression pressure is close to 200 psi once the compression release is overcome by centrifugal force.

I tried to attach a video of my cranking test after I reassembled my BV350 engine so you could see the compression release mechanism on the end of the cam sprocket, but the forum won't allow me to post it.

Thanks for the explanation.
So this mechanism is to assist the starter engine to get the engine cranking at a speed high enough for the inertia of the flywheel to easily overcome the compression stroke.
Is that it?
I did not know of that mechanism.

I've posted this so many times I feel I should change my handle to Stromrider.
My 2014 BV developed an intermittent hard start at 23,000 miles. Eventually it happened every time it was cold. I replaced the injector, coil/wire/plug cap, I tried a lambda sensor and CDI, no change. I messed up the ECU/throttle body cleaning it, so I had to replace it.
The only thing I didn't do is mess with the fuel pump. I think the check valve in the fuel pump was allowing fuel to bleed back into the tank. I didn't try starting fluid but I think if you remove the air filter, you can spray in a small amount just after cranking over the motor.
If it starts right away, then there's probably air in the fuel line before the injector.

Yes. Or more simply put, using a compression release requires a less robust starter motor, and also draws less current from the battery compared to trying to crank a similar engine without a compression release.

One other thing that some have claimed was causing excess cranking when cold is if the valve clearance gets tighter. I have adjusted the valves on mine and it didn't make a difference.

It is to be able to use a less strong starter motor, that was clear to me.

But if air gets into the fuel line, the cold start problem would happen in any temperature/weather? Not just in cold weather.