Vintage Vespa Forum

Vespa Restoration

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texanaussiefamily JT Thrasher
Bunbury, WA, Australia   AUS
hello guys, just acquired a 1965 150 sport vespa frame, with a vnb5m 125 1965 motor stripped down to replace drive shaft and bearings, noticed flywheel had sheared key and damaged main shaft have fixed that problem and then noticed cylinder had a 57.8mm bore not a standard 52.5mm. Leveled all surfaces and put back together, the motor has 78 lbs of compression. Set the timing to 25 degrees instead of because at 26 degrees as called for cant get enough out of stator plate for points to remain at 0.4mm. The carberator is a SI20.20od with 42 slow run jet, 160 air cal., and 102 main jet. The bike starts easy and runs decent cold and up to half throttle then all hell brakes loose. Does anyone have which variable is wrong or which can be changed to fix. The compression seems low to me but the timing not setting correctly does too. This motor has had some real unexperienced folks messing with it. Vespa is new to me but have worked on a lot of other bikes.

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Sammydeconinck Pascal Leirens
Oudenaarde / Eine, oost-vlaanderen, Belgium   BEL
Hi JT,
Can you check if a warmed up motor goes up in rpm ? So yes,change all the sealings.....
Greats from Belgium,

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1964 Vespa VNB 125

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