Throttle sticking
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GT 125 - 1967
Joined: 08 Mar 2020
Posts: 1
Location: Leicester
Sun Mar 08, 2020 5:02 am quote
Got a Vespa GT 125, 1967 thatís been sat in a barn for the last 10 years. Just getting it out and ready to roll but the throttle is sticking and not returning. Had a very quick look and seems to be a bar type.
Does anyone have any diagrams/ manuals referring to this before I do a strip down to investigate or is there a common issue.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 8066
Location: Victoria, Australia
Sun Mar 08, 2020 5:11 am quote
What manuals etc do you have already?

Start with checking the carb end to see that's moving freely, then WD40 around the throttle tube area - as much of it as you can see. That usually fixes it but if it's binding in the carb box it won't help.
Joined: 22 Oct 2011
Posts: 4399
Location: Tega Cay, SC
Sun Mar 08, 2020 8:24 am quote
On a lot of the older Vespa, there really is not of spring tension going on, that is you pretty much have to close down the throttle by the hand grip. Kinda a built in cruse control. Now, if it is a carb problem, say the slide is sticking, then you are looking at a strip and rebuild.
Joined: 11 Jan 2007
Posts: 7687
Location: San Francisco
Sun Mar 08, 2020 11:48 am quote
by design they do not spring back to closed, but it should not be stiff in any way.

There is loop of spring steel between the throttle tube and the handle bar casting near the grip. This holds the position of the throttle to allow hand signals to be made with the right hand.

When greased and working well there is very little resistance to opening or closing the throttle, but it will still hold the position. When the grease is gone it will open ok, and then be hard to close.

If you remove the loop, it will spring closed like most modern throttles.
Joined: 05 Oct 2013
Posts: 99
Location: Santa Cruz, CA
Mon Feb 22, 2021 6:07 pm quote
So a bit embarrassed to mention my dumb move but if it helps... make sure you don't close the idle adjuster too tight. I found out today that the screw extended to far and was catching on a maker's stamp on slide. It was causing the slide to stick open. Why my idle screw can be closed too tightly and the engine still runs is something I have to still figure out.
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