Modern Vespa

I did some searching for GTS and cold stalling and didn't find anything.

Until about a month ago my GTS 300 was running like a champ. Still does except when cold. Now, even if I let it warm up a minute or two, it always stalls on my first stop after a cold start. Never happens after a warm start.

The first start works as expected. No gas applied and starts right up. After the stall, I have to give it some gas to get it to start again.

Any ideas?

oh, I cut the evap hose a few weeks ago, but hasn't helped.....

Just a thought, But check your spark plug wire, be sure it is fully seated on the spark plug. I have a constant problem with mine coming unseated, runs fine but idles rough. It comes unseated going over railroad tracks or speed bumps.
Jack

Valve clearances.

I'll look into that, but I only have 2K miles thus far. Can they need adjustment that soon?

mine seems to idle fine when warm. And idles fine on first start. It is just when I give it gas and move it to the first stop that it stalls. Anyway, I just went and made sure it was seated properly, so let's see if that helps when I leave for work.

Did you cut both ends of the evap system? There's the host leading from the filler neck to the left cowl, and then there's the hose leading from the intake manifold to the lower front portion of the left cowl. Both need to be cut.

No I did not! I only cut the one from the filler neck. Thanks!

It was a good thought! Tonight before leaving work I made sure to wiggle the spark plug wire to make sure it was fully seated and for the first time in a while it didn't stall on the first stop. Thanks!

brilaz: As Jess pointed out, both ends need to be cut and after you cut the one going to the throttle body, it need to be plugged (on the throttle body side). If you have a partially blocked canister and you only cut the overflow line, you would still be getting the same effect as if both lines were still hooked up.

If it's the spark plug, the cap must be seated firm & tight on the top of the plug or it will keep coming loose.

OK guys before this thread completely goes bad with "they said" I will tell you I have experienced two 300's with this problem.

The problem is a faulty fuel filter. Some were made poorly and they are not sealed in the fuel pump and they leak.

It's under warranty, go get it fixed for free.

Best,
SDG

This is when the valves are fully broken in, and it's a good idea to have them adjusted.

Well my 300 has been with the dealer for a week now and yesterday they told me what the problem is. They need to replace the throttle body assembly.

It has been slow for them to debug since the stalling only happens when the engine is dead cold, but after a lot of back-and-forth with piaggio they tried the throttle body assembly from another bike and that fixed the problem. So now I am waiting for the part. Hmmmmm, it didn't occur to me to ask why they couldn't just leave the one from the new bike on mine rather than making me wait.....

You should call them back and ask them to do just that. I got my new engine quickly because they sacrificed an engine from another new 300 Super on the showroom floor.

What Benny said.

Isn't the throttle body assembly combined with the ECU and coded to a particular bike/key?

You can use the old ECU with the new throttle body, but then you have to zero the TPS - this is the one and only situation when this should be done.

Well, it is supposed to rain here over the next few days. I'm not an all weather rider, so I can wait a bit more. But I will definitely ask for them if they can do this if it looks like it will take a long time.

Well they say they tried one off another scoot to verify the diagnosis.

So after waiting four weeks for the new throttle body assembly to be installed by my dealer, it finally arrived. I was confident since they had claimed to have tested one from another bike and it fixed the issue. After installation guess what. The problem was still there. I was too disgusted about not having my scooter for a month to leave it any longer. They said they would call piaggio and get back to me. Nothing. Bah!

I guess now I will push the other two possible solutions mentioned in this thread. I did push both of these (faulty fuel filter or valve adjustment) with the dealer when I first brought it in, but they pretty much wrote both of these off.

Until then, I will have to warm it up for 5 minutes before leaving anywhere....

After fitting the new throttle body, did they zero the TPS (throttle position sensor) using the diagnostic unit?

I completely stand by what I said up a few post's. It is almost certainly the fuel pump, have them crack it open and they will probably find a break in the seal of the fuel filter.

I try, I try.

SDG

Rotten bit of luck with your 300!!! I would be tempted to insist that your dealer gives you a 300 loan bike at Piaggio's expense. It is a new bike after all said and done and you shouldn't be without a bike for any longer!!

My 300 does something like that too. Although mine doesn't die, it does have a definate stumble when I first get going in the morning. It clears out after a few stops but even if I let it warm up for a few minutes it does it. Let me ask you this. If you are going 30mph and you let off the gas and coast does yours pick up a little when you get to 25mph?

I appreciate your help here and will push on my dealer to do this. Many thanks!

I don't know. They are actually still coming up to speed on the modern vespa technology and have been spending a lot of time on the phone with piaggio reps discussing how to do all this properly. However, I will be asking this question of them to make sure. Thanks!

Once mine warms up I don't notice a problem. Only cold. Started at about 2K miles. Before that it was fine.

As for letting off the gas going 30, I can't say I've noticed anything like you describe. I'll give that a try on my way home tonight.

Tough luck on the diagnosis so far.

If you can - try to actually physically show them this thread on their own computer - there has been a dealer and a couple of great mechanics who have chimed in on it so it certainly seems as if they should be 'persuaded' to listen to their advice...

Good luck,

Desi B.

Plus they might actually get to read the workshop manuals!

Yeah, I left them a message this morning to call me with their email address so I could send them the link. Alternatively I will print all and plant it in front of them.

I just got my 300 back and JimC gets the gold star. They checked the fuel filter and it was fine. They checked some other misc stuff. Then eventually got around to Jim's suggestion to adjust the valves. Bingo. No more stalling.

The upside to all this was that they gave me a 900cc Triumph Scrambler as a loaner after the second trip to the shop and it was nice to see what living with a motorcycle was like for a couple of weeks.

Whacko! Always my first thought when the problem is related to poor idle or performance until fully warmed up. Most of the other suggestions would normally have been evident at all engine temperatures.

Glad it is finally sorted.

thats why there paying jimc the big $$$..... keeps our 300 rolling...