GT200 starts then won't run
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Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Wed Nov 27, 2019 1:42 am quote
A couple of weeks ago we took Sofia on a Club run. We covered 260km in the day and she ran like a top. We were 2 up and had an awesome day. The next morning I got her out to take to work and she went from the garage to the front gate and stopped - and wouldn't restart. She occasionally fired and ran briefly but refused to run consistently. So, I took Francesca to work and came home to take the carburettor apart, the problem certainly appeared to be fuel related. I found nothing obvious in the carb so put it back in and started her up and she ran for a while so I put her away for the next time. On the Wednesday we went through the same problem, so I later checked that the fuel pump was pumping, and therefore the fuel tap was opening. I couldn't get her to start and run so I took her to the shop. They have had her for about 2 weeks and couldn't get her to fault. They had taken the carburettor completely apart in case I had missed something, and they checked the float was indeed floating etc. The SAS is already disabled so they sent me a note to say she was ready. The technician started her up and rode her around to the trailer ramp, then used the motor to power her gently up on to the trailer. All the time the engine was running until she was up against the chock and we started tying her down. He then turned her off.
So, at home I started her once she was off the trailer and went to move her to the garage and she hesitated, then stopped. I restarted her and with very gentle application of the throttle I got her to move right up to the garage, less than 20 metres, and she died and wouldn't start again. I rang the shop and they are as confused as I am, they need her back obviously. I went out later and she started, idled briefly then stopped and wouldn't restart.
What gives? - Go!
Ossessionato
2006 Vespa GT (Rocket): 2005 Vespa GT (Razzo): 2006 Vespa GT (Crash): 2007 Vespa GT (Vanessa): 2009 Yamaha Zuma 125 (Zoom): 2018 Yamaha Xmax (Max),
Joined: 26 Sep 2006
Posts: 4243
Location: Jacksonville, Florida
Wed Nov 27, 2019 2:44 am quote
You might want to check the electrical side.

Bad battery connections or bad coil can cause those issues.

Bill
Member
Stella
Joined: 28 Jan 2012
Posts: 47
Location: USA
Wed Nov 27, 2019 4:43 am quote
That is a carbed model? Try disconnecting the hose running from the intake "manifold" and see if it runs. Also try i with the gas cap off (maybe try this first but my guess is removing the hose will do the job).
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 37878
Location: Pleasant Hill, CA
Wed Nov 27, 2019 9:01 am quote
When they cleaned the carb, did they completely remove the float and the inlet plunger? I had a similar head-scratching fault on my GT200 earlier this year - in the end it was that plunger sticking slightly - just enough to stop the fuel flowing into the carb. It can be removed by using a pop-rivet as a drift on the small roll-pin. Eventually found after at least ten complete (except for that bit) carb dismantle sessions, over a period of a couple of weeks.
Addicted
2006 LX150 (carbed) | 2007 GT200
Joined: 29 Jun 2016
Posts: 793
Location: Toronto
Wed Nov 27, 2019 1:49 pm quote
redstella wrote:
That is a carbed model? Try disconnecting the hose running from the intake "manifold" and see if it runs. Also try i with the gas cap off (maybe try this first but my guess is removing the hose will do the job).
If you do this, I think you will have a direct opening to the intake manifold and therefore a significant air leak? You'd have to cap the line? And make sure you are disconnecting the evap line, not the vacuum line to the fuel petcock.

Unless you mean to remove the hose from the carburetor to the evaporative control system?
Member
Stella
Joined: 28 Jan 2012
Posts: 47
Location: USA
Wed Nov 27, 2019 2:35 pm quote
Correct-the line doesn't go to the manifold, it goes to the float bowl. Thanks for the catch!

The symptoms point to blocked venting of the bowl.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Wed Nov 27, 2019 8:40 pm quote
Thanks to all who have replied. Despite being in the naughty corner all night she hasn't learnt her lesson so she went back to the shop today. Fortunately, in a perverse sort of way, she misbehaved brilliantly. I discussed some of the suggestions with the dealer and his thoughts remain with fuel problems as it will start and run then peters out as if the float chamber is empty.
I will keep you all informed.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Fri Nov 29, 2019 4:07 am quote
I got a call after normal hours today to say that Sofia was being a perfect lady again after some minor work. The carburettor was again dismantled and the pilot jet was inspected by both the original mechanic and the owner of the business. They blew everything out and between them saw the pilot jet clear - or not - depending on the moment in time. So, they have installed a slightly bigger pilot jet and have raised the float level fractionally and got her started. They then left her to idle until she was fully hot 🥵 then they took her for a couple of squirts up and down their service road and she never missed a beat.
Unfortunately I donít have her back yet as we were walking out the door for the evening, hopefully in the morning.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Mon Dec 09, 2019 12:25 am quote
Frustration!
So, I picked her up on the Saturday morning and started her and rode her on to my trailer. I tied her down and brought her home, took her off the trailer and she ran for - you guessed it - about 20 seconds. And she wouldnít restart, very weird. So, I pushed her back on the trailer, and sent a text to the shop owner. I took her back on the Monday, carefully unloaded her and went to demonstrate how she refused to start and she didnít; refuse to start that is. So, we let her idle and she ever faltered, she ran up and down the rev range beautifully so eventually I went for a ride of about 1 kilometre and she felt better than ever. Keep in mind that nothing had been done to the engine since the Friday, but she was running like a top. So, she came home again, I started her on the trailer and she ran well and kept running so I unloaded her and she kept running. During the day I started her a couple more times and she gave no problems. Now, I have taken her to work twice and she has started and run beautifully and today got a new tank of gas and she continues to go well.
Fingers crossed.
Ossessionato
2015 GTS300, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 4277
Location: San Diego, CA
Mon Dec 09, 2019 6:36 am quote
Trailering a carbed scoot can give some starting issues after, the float is bouncing a lot.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Mon Dec 09, 2019 12:11 pm quote
sdjohn wrote:
Trailering a carbed scoot can give some starting issues after, the float is bouncing a lot.
That certainly crossed my mind more than once, but it started misbehaving after sitting overnight in the garage, and repeated that behaviour more than once.
We think there has been a vacuum issue that has been solved inadvertently by trying the various tests the shop carried out. Now we are absolutely sure that sucking on the vacuum pipe both opens the fuel tap and activates the fuel pump. It's almost as if there was a bit of crap in the vacuum line that has now cleared itself and probably exited the scooter via the exhaust.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Mon Jan 13, 2020 2:38 am quote
Very Frustrating
So, after weeks of being the perfect lady, Sofia let me down tonight - away from home. Left my meeting and was headed for home and she appeared to run out of fuel. The fuel gauge disagrees.
I took the vacuum line off at the head end and the suction there is good. I replaced that end and took it off at the fuel cock end and the suction there is strong. I replaced that and took the fuel line off at the carb inlet and successfully pumped fuel on to the footpath. Soooo . . . I took the spark plug out and checked that I had spark which I did. All this on the side of the road of course.
So I let home know and took an Uber home to pick up the car and trailer. I went back with both keys in case the code system had decided to be a bit petulant, but neither key would make it start. The red code light is flashing nicely when it is turned off. It turns over strongly on the battery, there must be a limit to how long I can keep trying but I haven't found it yet.
So friends, any new ideas for me? Please?
Ossessionato
2014 Commuter BV350(43,000)/2015 Scoot Life BV350(10,000)/2010 El Diablito SH150i(29,000)
Joined: 27 Dec 2013
Posts: 2326
Location: Orange Park Florida
Mon Jan 13, 2020 2:59 am quote
Re: Very Frustrating
pigletpilot wrote:
The red code light is flashing nicely when it is turned off. It turns over strongly on the battery, there must be a limit to how long I can keep trying but I haven't found it yet.
So friends, any new ideas for me? Please?
https://scooterpartsco.com/vespa/gt-200/gt-200-electrical/cdi-for-vespa-gt-200?zenid=e66e323d9a3e47230bdf4cc2b8c284a6

No one want's to just throw money at a problem but this is where I'd start.
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 37878
Location: Pleasant Hill, CA
Mon Jan 13, 2020 9:09 am quote
Re: Very Frustrating
breaknwind wrote:
pigletpilot wrote:
The red code light is flashing nicely when it is turned off. It turns over strongly on the battery, there must be a limit to how long I can keep trying but I haven't found it yet.
So friends, any new ideas for me? Please?
https://scooterpartsco.com/vespa/gt-200/gt-200-electrical/cdi-for-vespa-gt-200?zenid=e66e323d9a3e47230bdf4cc2b8c284a6

No one want's to just throw money at a problem but this is where I'd start.
No way I would start with that!

First, try spraying some starter fluid into the carb air intake - if there's any sign of it coughing or starting then, remove the carb and give it a good clean and check-over.
Molto Verboso
Gina, 1965 Vespa 180SS, Bella,1968 Vespa 150 Super, (Both NZ new Airco assembled), Francesca, 2006 Vespa LX150, Sofia, 2007 Vespa GT200
Joined: 21 Jan 2015
Posts: 1289
Location: Hamilton, NZ
Mon Jan 13, 2020 8:16 pm quote
Needle Valve
I have just pulled the carburettor apart and cleaned everything and initially the needle valve was sticky. I think I have probably found the culprit and will order a new seat and valve. In the meantime, I have clearly put it back together slightly wrong; it runs but a bit roughly, and on opening the throttle blows black smoke so it's running rich. The only part that fell out without me actually seeing it was what the Service manual describes as the emulsion tube. It looks like a nipple with a collar in the middle and I thought I put it bach exactly as the picture in the manual shows.

Is this likely to cause rich running if it is upside down?
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