Modern Vespa

I have an 05 GT200L and it has almost 40,000 miles on it. The other day on the way to work after stopping at a light it started to sputter like it was running out of gas. I checked the gas and the tank was nearly half full. I filled the tank to be sure, but the problem was still happening. The scoot idles fine, but when you give it throttle it cuts out intermittently and often dies. It is a lot like the feeling you get when you are running out of gas. So I removed the fuel line at the carberator this morning and no fuel came out. I crank the engine over for 4 periods of 10 seconds and saw no fuel coming out the hose. I can see some fuel in the filter, but cant get anything to flow out the hose. Shouldn't I be getting a flow of gas through the hose when cranking the engine? Anyone know the best way to check the fuel pump and fuel flow? Your help is greatly appreciated.

Does a 2005 GT200 have a fuel pump or just a vacuum-opened fuel tap and gravity flow like the LXs? If it has a tap, you can test that by removing the vacuum line to the tap from the intake manifold and simply sucking on it to see if the fuel flows.

The GT200 has a vac operated fuel pump.

Yes it has a fuel tap and a vac fuel pump. Should fuel be flowing when the starter is cranked over? I cant get a drop out of it right now. What provides the vacuum for the vac fuel pump?

Dunno if it is the same fuel system as the gt125 but on mine when i disconnected the fuel pipe from the carb, fuel flowed through upon turning the throttle.

Also my symptoms were very similar to yours and it turned out to be the lead coming from the spark plug. Had a small coolant leak which was dripping on the lead and into the spark plug cylinder. Dried it all up and replaced all the cooling hoses and has been okay since.

Worth a look maybe

dk`

So I replaced the fuel filter and all the gas lines and also got a brand new factory carberator. Now I am into it for $250. I started it up after putting on the new carb and it idled well. I drove it a block or two up and down my street and it ran beautifly. Tried driving it to work today and it did fine until I got a mile out, then it started to sputter out, even backfire a little. I managed to get back home under the intermittent pulsating of the throttle. It seems that when the engine warms up the problems start. Anyone have any suggestions? Not sure what else I can replace or check at this point. Thanks!

Hey guys,

New to the site, but hopefully I can help. I had a customer's GT200 that was doing this for a little while and we've got it sorted out now.

If you disconnect the fuel line from the carburettor and blow compressed air up the fuel line in the opposite direction of fuel flow, there's a very good chance that fuel will start flowing again. On the one we had here, the EVAP lines had become blocked with deposits, so when the fuel level got low, the tank couldn't breathe, causing a greater vacuum inside the tank than the carburettor was drawing; therefore impeding fuel flow.

Ensure that all the vacuum lines responsible for tank ventilation are clear (breather purge valve, overflow tube, etc.) and that the tank can "breathe". Of course, discovering this remedy required that I eliminate a blocked fuel filter, faulty fuel tap diaphragm, faulty fuel pump or a worn carburettor seat / needle from the equation!

Let me know if this helps.

Britishbyproxy,

Yet another reason to elimiate the EVAP system. Nice catch.

Please tell me that you didn't start replacing parts and then diagnose the problem...

Cheers,
Bob

Bob,

No, it was much worse than that...

The scooter was sitting in a corner of the shop when I started working here, with a new fuel pump hanging in a bag from the handlebar. Apparently one of the motorcycle mechanics "diagnosed" (read: guessed) that this was the issue.

Once the bike came back a second time with the same issue, I figured to start from base, as if it had never been in before, and eliminate parts one at a time.

Oddly, what made me think of the "negative vacuum" diagnoses was remembering a similar situation on an old Triumph Bonneville I had years ago. The same symptoms occurred, and after pushing that heavy old pig two miles (with half a tank of fuel!) I commenced pulling the carburettors apart multiple times. I'd fill the tank, ride it down to around half full, and the problem would reoccur. After a great deal of perplexity, it turned out that the gasket on the fuel cap had swollen just enough to block the vent hole in the cap. 26 cents at the hardware store got me a new gasket; riding a Triumph got me in shape by pushing it all summer!

My fuel and evaporative systems are working fine and the tank is full of gas. The scoot runs like a champ until it warms up. Then it starts misfiring. I talked with a trusted scoot mechanic here and he is pretty sure that it is the stator that is the problem. That is one part that tends to fail when the scoot warms up to operating temperature. Anyone run into this? Any other ideas are greatly appreciated.

Ataritron,

Have you checked the charging rate on the scoot? 13.8 to 14.2 is normal.

Yes, I did a test of the charging voltage and it was right at recommended levels around 14V+-. I also checked the stator and it check out too. Could it be the HT coil or the spark plug? Running out of ideas.

Did you troubleshoot this further? Fuel should be flowing if the motor is cranking.

I am very interested in finding what is going on here.

I have has a similar problem, almost exactly, as a mater of fact: GT200 stalling.

She has been sitting until now because I have had other issues to resolve, but I am soon able to get back into seeing what is wrong.

I was just getting ready to order a new fuel line with filter, and a new fuel tap.

Before I do, I think I will try the compressed air thing. Air is free.

I have the EVAP hose disconnected. Where did you push the compressed air into?

<edit> Oh, I just went back and re-read this:

After further checking and testing it appears the pickup coil may be the problem after all. This is part of the stator. The resistance when tested was outside that specified in the shop manual. I am going to do a voltage test tonight and see if that also reveals a problem. My gas is flowing and the fuel system is fine, this is definitely a spark advance problem.

After testing the stator and pickup everything seemed to check out fine. So I tried replacing the spark plug to be sure. The scoot fired right up and has been running great for the last 25 miles of testing at various speeds. I have learned to now always look for the inexpensive, cheap solutions first. I am so glad I didn't spend any more money.

I am glad I replaced the carb though because the scoot runs so much better than it has in years. My old carb had fins broken off on both sides of the diaphragm shaft. One of those pieces I actually had to fish out of the cylinder.

So happy to be on 2 wheels again!

Check that the diaphragm valves are not sticking. Also in sure that the fuel cutoff diaphragm valve is operating correctly. Additionally ensure that the O-ring for the vacuum on the fuel cutoff valve is in its seat and sealing correctly. I had extensive problems my carburetor after having my bike serviced. In desperation I pull the carbie apart myself and discovered the O-ring have not been replaced in the fuel cutoff valve body. When I replaced this and did a full clean on the carburetor, the scooter runs like a dream. I have attached a photo of the offending O-ring.

Additionally if you are using the service manual from
http://www.jettin.com/PiaggioProducts/GT200Workshop.pdf
the photos on page 193 are not of a (Kehin CVK 30 Carburetor) but instead of a (Walbro WFV-7P Carburetor).

Hi I have a 2003 GT the fuel wasn't flowing to carburetor as ( far as I can tell) so bought both a new petcock and pump on eBay and cleaned lines as far as to filter and flushed tank with clean gas, alas still no flow of fuel. Has any one got an idea of what's going on? It was working like a dream until I stupidly ran it dry and refilled the tank so my guess was dirt in some part along the line which I why I replaced those parts. I am reluctant to fiddle with carb. as it seems rather complex for my limited skills.

Hi. I am a complete newbie working on bikes or cars. The most I have done before is oil change and transmission oil change on my car.
I'm learning everything ever so slowly.
Got a gt200 2006 that was said to be working pre covid and hasn't been started in over a year. The owner said in his attempt he changed the spark plug and put in a new battery but it didn't change anything and he used it as an excuse to convince his wife to get a new faster bike.

What I have tried after reading and rereading and hiurs and hours YouTube videos.

What I have tried
Replaced fuel filter on the line. Replaced main fuel line with clear line to carb. Replaced fuel tap and the hoses connecting to the t.

Replaced fuel with fresh 93 octane although I think the owned already did that.

The Clear line allowed me to see that no fuel was being pumped to the carb.

I tried spraying started fluid and no go.

Occasionally after trying to part it over 1000 times I would get a burst of it attempting to start while reving trying to start. But that was it.

I then attempted to clean the carb by blowing out the hole w carb cleaner, as well as both ports and took off the top plastic needle. But did not have any brushes and felt comfortable enough to take it apart further. Also the screws are stripped on it as it seems perhaps the pervious owner might have attempted this. Fluid came out of it. (Kehin CVK 30 Carburetor)

Thinking it may be the fuel pump. I tested it by sucking on tube and fuel was coming out of it.

I then saw a YouTube video to bypass the pump. So I just made a waterbottle with a cap and connected it directly to carb. No fuel was being pumped into the carb with this method either.

I took off the air box and the air filter was soaked w fuel. I could feel the air blowing when trying to start. I took out air filter and out the cover back on.

Still not getting fuel being sucked by the carb.

Now I can't even get it to burst for a split second like before.

So with my limited knowledge. I don't know what to try next?

remove the carb, strip it and dip the body and jets. blow out all the passages and jets with compressed air, check that the float or float needle isn't stuck in place (likely float needle) clean everything really well and reassemble properly. test that the accelerator pump and choke are operating properly.

clean out your airbox and filter (replace if it's roached) re-oil and reinstall your air filter. check your vacuum lines and intake manifold for cracks.double Check the plug is properly installed and that the cap is fully seated. I'd check for spark at the same time.

that should get it to at least pop and fart and you can fine tune it from there.

Realistically, the quickest and probably cheapest way to fix it right is to find a competent mechanic. You don't have the experience to troubleshoot and can easily throw money at it by replacing good parts with new parts or break something. Every competent mechanic or technician has both broken something and made a problem worse. That's part of the learning process. I have paid thousands of dollars to repair work I did on my house after watching You-tube videos. Do you want to ride a bike that runs or to train to be a Vespa mechanic? If you send me a PM with your location, I might be able to point you toward someone who knows what they're doing.

I am located where scooter mechanics charge $170 per hour. Bay area California and gas is currently avrg $5.40 a gallon. So yes I want to learn. I only paid $100 for the scooter. So even if I completely destroy it in the learning process it will still be worth the learning experience.

I have not replaced the vacuum lines. But I did try to bypass the fuel system entirely with a makeshift waterbottle premium octane connected directly to the carb. The fuel line fills but would not suck any of it in.

Are there any cheap Chinese knock off carburators that are compatible to do a direct swap. Or a place I can mail in the carburator for a full reassembly and cleaning as again it is super expensive where I live.

It is easier to learn to wrench on a working scooter doing basic maintenace than it is to attempt to troubleshoot something that you are not sure what needs to be fixed. How much is your time worth?
I would pay a local shop the $170 for an hour of labor to prove to you the following:

1. Spark
2. Adequate Compression

Hopefully by the end of that time with the mechanic they will be able to show you your scooter running (albeit briefly) on starting fluid.

Then, following online videos and write ups, remove the carburetor and clean it per the instructions. If it has sat unused for a year, the carb likely needs to be cleaned even if you do have a fuel pump problem. If screws are stripped out and cannot be removed easily, you will have to drill and remove using a screw extractor kit ( $8.99 at harbor freight) or source a replacement carburetor.

Welcome to Modern Vespa! This is a very supportive group and I think you will find folks are happy to help. Take photos and provide as much information as possible.

https://scooterpartsco.com/ricambi/030-piaggio/carburetor-for-vespa-gt200

problem solved!

or roll the dice on amazon with a chickety-china 30 CV and see what you wind up with.

1- down load and PRINT the service manual, put it in a three ring binder
2- buy decent tools
3- SEARCH FUNCTION ON THE FORUM

to reiterate: replace your vacuum lines, clean your airbox and air filter- or replace it (it needs the air filter to run properly) check your intake manifold, check the plug and HT cap, check for spark, rebuild your carb. there are plenty of threads here on these subjects and I'm sure there's a youtube tutorial somewhere, but start with scooter west.

worse comes to worse, box it up and send it to me. I'm in LA and USPS flatrate would be $15 coming and going. in the mean time I'll scrounge around and see if I can dig one up in my pile of parts.

also, post a wanted ad in the classifieds, maybe somebody has a spare.

I understand that you're new to this, but there's not magic wand to wave and make it all work, and none of us have crystal balls over here so you gotta do some of the heavy lifting. read, research, ask questions, break shit, learn from it. rinse and repeat.

ETA:

Sounds like a party. You can probably get it apart with a hammer and a crescent wrench, and maybe a screwdriver to pry off whatever you can't hit with the hammer.

Be sure float level is correct.

Float level and needle height aren't really concerns with modern cvk carbs, unless someone got in there previously and "fixed" it.

Look at the floats to be sure they have no fluids in them. I had a time getting an old 2006 Vespa running correctly even after altering the accelerator pump diaphragm which had rotted out. In the end after pulling the carburetor apart around Six times, I tried blowing through the gas tube going into the float bowl and found the floats were shutting off the fuel into the float bowl way too soon. Adjusted until I could blow through the same gas tube until the float line's (where the floats were welded or melted together) were level with the carburetor when held level. Reinstalled it and fired right up and I rode it for 30 minutes. No problems. I'm still waiting for battery, horn, keys and front glove box closing parts.

Opps, wrong post reply.

Hey snowboard, where in the bay are you?
I'm struggling to diagnose my Vespa gt200, but more than happy to show you how to properly go through a carb if I could toss yours into mine to rule it out. (Someone messed with mine before I bought it, and I don't know if it's the problem or not). I usually tinker Tuesdays and Thursdays, and some Saturday mornings in my garage in SF

Maurice
408-648-6919

Also, Old link, that's a good idea to check float bowls! I'll have to pull mine back apart in the morning and double check it.

2006 VESPA GT200
Same problem. Would go for about 10 minutes and then get starved for fuel. Solution was to replace the little plastic vacuum-driven fuel pump. Not expensive.