GT200 not starting after carb clean
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Vespa GT200
Joined: 02 Feb 2019
Posts: 4
Location: Sydney
Sun Feb 03, 2019 12:21 am quote
Hello internet friends!

Alrighty so I'm trying to get my mum's GT200 up and running, it's probably been sitting around for 6+ months unused (she's promising to actually start riding again). What I've done so far:

1. Drained fuel
2. Flushed and refilled coolant
3. Cleaned the carby, checked the main, idle and choke jets all seem clear and can get carb cleaner and wires through no problem. The float seems right, accelerator pump appears to be working and the slide is free.

Now after putting everything back together the engine turns over but won't start. There appears to be spark as it will run on starter fluid down the manifold but as soon as I stop the spray the engine cuts out. If I try the throttle with the starter fluid it sounds like the engine is getting starved.

Now two things might be contributing to this, the fuel intake on the carby might be clogged if I spray cleaner into there it doesn't seem to flow through to the needle.



Is there a way to check that fuel can actually get into the carburetor or to clean that line?

And secondly I was under the impression that the fuel line should be under vacuum and wouldn't leak when I disconnected the carburetor but I managed to drain the entire tank with the carby removed. I'm thinking this might indicate a problem with the vacuum lines.

Any advice would be appreciated.

Cheers!
Addicted
gt200
Joined: 17 Apr 2011
Posts: 765
Location: morrison, il. u.s.a.
Sun Feb 03, 2019 3:42 am quote
wont start
you may have a bad fuel tap, also after replacing that, i would replace the fuel and vaccume lines as well.
Addicted
2006 LX150 (carbed) | 2007 GT200
Joined: 29 Jun 2016
Posts: 685
Location: Toronto
Sun Feb 03, 2019 3:51 am quote
Welcome!

In what state is the battery?

If you connect a temporary line / tank to the carb, does fuel come out at the float?

I don't think the fuel line itself is under vacuum. But you are right it should not flow fuel with the bkke off, even if you remove the carb.

The situation is that the fuel system has *two* lines.

One is a vacuum line (no fuel) - it "pulls" on the fuel petcock when the engine is on. In this way, the petcock should only allow fuel flow when the bike is running. It sounds like yours is not working and stuck open. Replacement part is cheap.

The other line is the fuel line through which fuel flows when the petcock (and carb float valve when carb is in place) is open.
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lx 50
Joined: 09 Oct 2017
Posts: 931
Location: Brighton
Sun Feb 03, 2019 4:01 am quote
Also once you’ve had it all apart and drained the carb, you’ll have to turn it over for probably a minute before the fuel gets into all the right places.
Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
Joined: 21 Oct 2005
Posts: 7270
Location: The state of insanity, SoCal
Mon Feb 04, 2019 2:47 am quote
take the carb, as seen here-- without the bowl on it and hold in your hand, as if mounted to the engine. actuate the float and watch the needle.

does it move up and down freely? if good, then carry on. if not figure out why.

now in the same position, with the carb in "running position" and not messing with the float, squirt some juice down in there (fuel, brake clean, carb clean) and see if it dribbles out.

if it comes out, you don't have a problem with an obstruction there.

move onto other diagnostics.

is fuel actually getting to the carb? did you connect all the vacuum lines properly? did you replace anything or mess with anything else while you were there.

anyway, seeing as that it's a GT you're probably looking at throwing a fresh intake, fuel lines, filter, a tap and vacuum lines on it anyway. might as well get that out of the way while you've got it all apart.

hth!
-g
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Vespa GT200
Joined: 02 Feb 2019
Posts: 4
Location: Sydney
Mon Feb 04, 2019 5:09 am quote
Thanks for all the tips guys!

New battery, confirmed the voltage and did try cranking it for a while.

Will definitely recheck the vacuum and fuel lines.
Quote:
take the carb, as seen here-- without the bowl on it and hold in your hand, as if mounted to the engine. actuate the float and watch the needle.

does it move up and down freely? if good, then carry on. if not figure out why.

now in the same position, with the carb in "running position" and not messing with the float, squirt some juice down in there (fuel, brake clean, carb clean) and see if it dribbles out.

if it comes out, you don't have a problem with an obstruction there.
This was the test that I was looking for. The needle does move up and down but when I spray some carb cleaner in the fuel line nothing comes through the needle. I'll get a punch tomorrow and take the float and needle out. I'm guessing if there is any obstruction I can just clear it with some wires?

Cheers
Veni, Vidi, Posti
2008 MP3 500, 2013 BV350
Joined: 13 Oct 2012
Posts: 7107
Location: Ashburn, Va. Home to the Internet
Mon Feb 04, 2019 5:14 am quote
ambertx wrote:
Thanks for all the tips guys!

New battery, confirmed the voltage and did try cranking it for a while.

Will definitely recheck the vacuum and fuel lines.
Quote:
take the carb, as seen here-- without the bowl on it and hold in your hand, as if mounted to the engine. actuate the float and watch the needle.

does it move up and down freely? if good, then carry on. if not figure out why.

now in the same position, with the carb in "running position" and not messing with the float, squirt some juice down in there (fuel, brake clean, carb clean) and see if it dribbles out.

if it comes out, you don't have a problem with an obstruction there.
This was the test that I was looking for. The needle does move up and down but when I spray some carb cleaner in the fuel line nothing comes through the needle. I'll get a punch tomorrow and take the float and needle out. I'm guessing if there is any obstruction I can just clear it with some wires?

Cheers
Try compressed air first.
Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
Joined: 21 Oct 2005
Posts: 7270
Location: The state of insanity, SoCal
Tue Feb 05, 2019 3:10 am quote
^^ this. after you've got the float/needle assembly free try blowing some compressed air thru.

you definitely don't wanna be stickin' no pokey or scratchy stuff up in there where the needle rides.

also, as to removal of the float pin. investigate closely. some only come out to one side because the pin is knurled/splined so double check that. use the smallest punch you can with the smallest hammer you can find. sometimes even the handle of a ratchet or screwdriver is better than some claw hammer you've got laying about. the towers that hold the pin are cast and will break if you go reefin' on 'em.

-g
Ossessionato
09 190s taormina
Joined: 08 Apr 2010
Posts: 2082
Location: Googleville
Tue Feb 05, 2019 10:44 am quote
ambertx wrote:
And secondly I was under the impression that the fuel line should be under vacuum and wouldn't leak when I disconnected the carburetor but I managed to drain the entire tank with the carby removed. I'm thinking this might indicate a problem with the vacuum lines.
Yeah, it's not supposed to do that. I second the recommendation on suspect tap and fresh lines.
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Vespa GT200
Joined: 02 Feb 2019
Posts: 4
Location: Sydney
Fri Feb 08, 2019 1:33 am quote
Well that did the trick!

The float valve was all gummed up



I thought it was just the little pin that was meant to move not the whole part.

Got it cleaned up and reassembled and the scooter starts!

For now it does take a minute or so of cranking to get it to start when cold but it's fine to restart once warmed up.

Thanks for all your help guys!
Addicted
2006 LX150 (carbed) | 2007 GT200
Joined: 29 Jun 2016
Posts: 685
Location: Toronto
Fri Feb 08, 2019 2:50 am quote
Great! I'm glad you found the problem and got it running

I still think you'll want to replace the petcock at the tank. You should not have had fuel flow with bike off, regardless of what was happening at the carb end.
Grumpy Biker
1980 Vespa P200e (sold), 2002 Vespa ET4 (sold), 1949 Harley-Davidson FL
Joined: 27 Oct 2009
Posts: 4681
Location: Chandler, Arizona, USA
Fri Feb 08, 2019 7:16 am quote
That needle looks really gouged up. Did you have to pry it out of the seat with a tool? I'd replace it.

-Craig
Hooked
BV 350
Joined: 22 Nov 2016
Posts: 354
Location: Nebraska
Fri Feb 08, 2019 8:44 am quote
save work
Usually I'll squirt carb cleaner down the fuel inlet of the carb with the float hanging down, to help clean the float needle and seat. A little low-pressure air down the fuel inlet can also help.

Need to be pretty careful when driving out the pivot pin for the float. Broke one of the 'ears' the pin goes through on a carb, early in my wrenching days, when I whacked on it too hard. Now I tap, gently, until enough pin protrudes that I can grab it with a needle-nose pliers and, rotating it gently, pull it out.

If you can solve the problem with the carb cleaner, better yet.

And I second the notion of never using wire to clean jets. On the float jet, a scratch on the sealing surface will prevent it from sealing. On pilot and main jets, a burr will change the flow characteristics. Carb cleaner and compressed air are your friends.
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Vespa GT200
Joined: 02 Feb 2019
Posts: 4
Location: Sydney
Sat Feb 09, 2019 3:06 pm quote
caschnd1 wrote:
That needle looks really gouged up. Did you have to pry it out of the seat with a tool? I'd replace it.

-Craig
Yea it didn't budge with the airgun so I needed pliers to get it out of there, will be replaced at some point.
Quote:
I still think you'll want to replace the petcock at the tank. You should not have had fuel flow with bike off, regardless of what was happening at the carb end.
I'm planning to replace the fuel system and the jets in the near future!

Thanks for all the help everyone!
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