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Vespa gt 125
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Has anyone fitted 07 engine to 03 model 125..looking at the pictures seems water pump has 3 outlets rather than 2..is this a problem..could I use a t or y piece to run from cylinder head..
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Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
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is the motor air cooled or water cooled? injected or carbureted?

the likelihood of the compatibility for a swap is very low. an 03 would be a leader series motor and the 07 would likely be a quasar series motor.

while the later motor will physically fit, the wiring would be a nightmare.
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No they are both leader engines just the water plumbing is different..but thanks for input
@greasy125 avatar
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Weird 80's Vespas & Cool Vintage Lambrettas
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UTC quote
sounds like you've got it well in hand then.
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Veni, Vidi, Posti
GT 200
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UTC quote
Is the water pump the same?
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Don't know if there the same as I bought the ped with the engine already fitted..from what I can gather carb model heads haven't got as many outlets as 06 onwards..I imagine it's to do with emissions..
It seems I have 07 head on original engine going by the codes.. I have blanked the hose with bolt and sealant.. now to see lol
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This is the extra outlet on the 07 head that needed blanking off
Forum member supplied image with no explanatory text
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Also this part needs a grommet ..the thermostat housing is different
Forum member supplied image with no explanatory text
@greasy125 avatar
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Weird 80's Vespas & Cool Vintage Lambrettas
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UTC quote
what's the other head look like and what do the pumps look like?
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I don't have the original head..this is how the bike came...
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GT 200
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I'm pretty sure the third outlet is a bypass so coolant can circulate in a loop before the thermostat opens. It wasn't on the US GT200 but appeared on the GTS 250.
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UTC quote
The bike was running when purchased but appeared low on water..signs of water leaks..the hose in question had a bung.. but seems to be leaking..
Looking at the explos the later heads have a bleed valve in the thermostat cover and would cover the 3rd hole..
I have a grommet for 3rd hole and thinking of putting a hollow bolt with a bleed nipple into the outlet to help bleed off the air in system once refilled..
Hopefully this will work 🙏

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