Modern Vespa

Hi everyone,

First post, but been having a recurring issue that my bike doesn't want to start in the cold (I live in Canada) and been having issues finding a good resource to diagnose this.

When the weather is warm it always starts right up, and will start right up if it's still warm from the last ride, but as soon as the temperate dips below 10°C or so the electric starter isn't enough to get it going; but with several dozens of kicks it may start.

This was a problem in the fall before going away for winter indoor storage on a battery tender. Picked it up this week, and the guy running the storage got it started (with many kicks he said, it's a somewhat heated garage) before I brought it home. Ran great for the 5-10km getting home, but the next day I can't get it running.

Curious what diagnostics I should consider when it seems so temperature dependant; I'm willing to take it for service if needed; but I'm interested to learn more of the maintenance myself where I can.

A few more notes:
- If you message "with a few pumps of the throttle/cold start procedure mine starts right up in the cold" you'll hurt my feelings out of jealousy (this is far too often the advice I find lol)
- I kicked it far too many times today and noticed the kick wasn't as smooth by the end; is this something I should be worried about?
- I noticed the 'choke warmer' doesn't seem to be warm to the touch after leaving the key on for a few minutes, could this mechanism be bad (based on the issues it feels like it could make sense?)

Next step in my mind will be to pickup a can of starting fluid, but from what I've seen this shouldn't be required so I'd rather try to run through other 'tricks' or diagnostics first so that I can reliably get it going on cold mornings.

Any insight is appreciated, I'll do my best to keep an eye out and test what I can tomorrow.

Is this a fuel injected or a carburetor engine? I believe 2019 was the start of fuel injection for Primavera 50, but please confirm.

If this is a carb engine, then you have a fuel delivery problem that is likely related to the auto-choke.
https://scooterpartsco.com/prima-50-air-and-fuel-c-3637_3650_3980/carburetor-heater-871314-p-36824.html

Great question, yes 2018 uses a carburetor, and I do believe it's the last year before they shifted.

Appreciate the suggestion, and glad to see it's not an expensive part. I'll have to order one and see if it works; as I mentioned, there's no noticeable warming happening with mine currently.

This one may take time to arrive but I'll update once I can test this.

I would rule out an old battery failing to provide enough juice before I started throwing carburetor parts at this problem. How does the engine sound when activating the electric start? If there's more draw than the battery can provide when the ignition is turned on (carb heater, ignition) then that would explain the difficulty starting and the eventual ability of the kickstart to work.

I'm not familiar with the carb on this 50cc but really don't know if the "carb heater" is supposed to generate perceptible warmth. Is that an "auto bystarter" choke system?

My bet is a failing battery. If you decide to replace it, consider an LFP (LiFePO4) lithium battery. They can provide higher voltage under load (they'll stay at 13V instead of 11V when starting) and will definitely help cold starting.

Appreciate the additional feedback.

Hmm, I'd say it generally doesn't sound odd when trying to get going with the electric start. At this point my battery is nearly dead from trying so much (lol) but otherwise it wouldn't have been my suspicion.

I will look into a new battery as this could be a good idea anyhow. As for the LiFePO4; I like the idea of a better battery, but unless I'm looking at the wrong items I'm having some sticker shock - appears to be 10X the normal replacements?? If it were a sure success in the cold I'd consider it, but a lot to shell out extra. Maybe the next time.

Weird trick (that was unsuccessful) but I tried placing something warm on the choke-heater to see if by some strange method it worked, but it didn't help. Obviously not a scientific trick, especially considering it's likely more finicky that I threw so much time trying to start it.

LFP batteries are now (in the US at least) about the same price as good AGM lead-acid batteries - USD 90-110, so CAD 125-155?

e.g. https://www.weizeus.com/products/weize-12v-5ah-lithium-ytx14-bs-group-14-500a-lifepo4-motorcycle-battery

If you look into the operation of the "auto bystarter" choke device - and again I'm not positive this is how the 50cc Vespas work - you'll see that they don't function by heating the carb, fuel, or air in any way. They heat a pellet of wax with the unusual characteristic of shrinking when it liquefies.

In a cold state, when the engine has been at rest, the pellet pushes a pin into the carb that blocks air and richens the mixture. Once the engine is started, a small heater inside the choke melts the wax and the pin retracts, NORMALIZING the mixture. As long as the engine continues to run, the heater keeps the wax melted and the mixture is normalized.

The point here: the failure mode of these chokes is in the richened state. So if there's a problem with the choke, hard starting is not the symptom.

I wish my snowblower had this type of choke. It does not, it has a manual choke.

Okay perfect, clearly my initial results stumbled into the wrong category then. I'll certainly invest the extra money in a LiFePO4 then - great advice!

Appreciate the added insight into the mechanism, that's really interesting - perhaps I honed in on this too readily: noticed one video mentioning it (part of why it was advised to leave the key on for 1-2 minutes before trying to start).

I'm too used to a manual choke on my old dirt bikes, so it's refreshing to have this 'smart' mechanical system instead - unless it somehow does end up being the culprit.

Battery will be first, then I'll go down the rabbit hole as to whether it stems from fuel delivery/the carb.

Without springing for a new battery, you can test the battery theory by using jumper cables when the temps are below 10C and see if the same problem persists. If yes, then battery is not the problem.

Have you fiddled with the carb mixture screw or the idle screw? Maybe it needs to be adjusted.

Before you try to start it cold, try spraying some brake cleaner or ether on the intake manifold. See if it makes a difference. Then when the engine is warm and running, spray on the intake manifold, see if the idle changes.

Thanks again everyone for the help!

After getting too in the weeds, seems the simple fix is likely the right one. In a case parallel thinking, I was able to jump the bike using my car (engine off of course, thanks to the earlier thread I found) and got it going.

Seems like the original owner already replaced the stock battery with a cheaper acid one (no shade to him, he did a lot of maintenance himself for his daughter who didn't have much time to really ride it). I'll replace it with a LiFePO4 and will report back once it's in.

FWIW, I cheerfully use cheap lead acid Mighty Max Amazon gel batteries in my scooters - just not the cheapest - and they seem to last 3 years.

With a kickstarter, and perhaps a lithium " pack in the carrier, premature battery failure is at worst a minor inconvenience.

The lithium installed batteries are impressive technology but a bit extravagant for my taste, at this price.

Update: Weather isn't as cold today, but replaced the battery with a LiFePO4 (wow, not that I cared but is it ever light) and it started right up.

In case it helps anyone, I bought a 'Tykool LFP7SL' to replace the acid YTX7L-BS that was no longer holding up. On Amazon Canada it was only 110 CAD, and has a screen to show voltage/power level.

Thanks again all for the help

Hey everyone,

Me again - seems I perhaps spoke too soon. Last night the temperature dropped again and it took several minutes of trying to get it started..

New battery certainly helped and was a worthy investment, but I'm curious if I should revisit any other suggestions.

Thanks

Get yourself a set of carb mixture screw screwdrivers, so you can mess around with the mixture screw (and also the idle screw). Set the mixture screw to 2.5 turns out. See what happens.

I had this exact issue with a Big Ruckus. I tested the auto-enricher. It was in spec. 65F or above. The scooter ran like a champ. When cold, it was almost impossible to start. I cleaned the choke port without even removing the carb. Remove the auto choke and find a straw that will fit. Fill it the Chem Tool B12. Let it sit over night. Do it again. Blow throw the port with your compressor.
Find out how far the choke needle is supposed to extend when warm. Check yours. Good luck.