Modern Vespa : Vespa 125 GT 2004 flat spot

Vespa 125 GT 2004 flat spot

hcurran

UTC

details

Hooked

GTS 300 Super '16, (GTS 125 Super written off in Jan 2022 - a 'SMIDSY' incident). Previously a GT125L and an ET4

Joined: UTC
Posts: 105
Location: Cheltenham, UK

hcurran

Hooked

GTS 300 Super '16, (GTS 125 Super written off in Jan 2022 - a 'SMIDSY' incident). Previously a GT125L and an ET4

Joined: UTC
Posts: 105
Location: Cheltenham, UK

UTC quote

Hi
Ive just resuscitated a 2004 GT. It has got a flat spot sometimes (particularly when engine is cold) when going from tick-over to running on "main jet". Pulling out of a junction say, I have to "nurse it" a bit to ensure it doesn't cut out - then off it goes!

Question is this. Is the "flat spot" likely to be caused by the weights and rollers - or could it be the carburettor?. Is there a jet in the carburettor that is in between the tick-over and running on a fairly full throttle? Or could the variator weights and rollers be the culprits?

Many thanks in advance

Hugh

jimc UTC details Moderaptor The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300 Joined: UTC Posts: 44337 Location: Pleasant Hill, CA
jimc Moderaptor The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300 Joined: UTC Posts: 44337 Location: Pleasant Hill, CA	UTC quote Almost certainly your valve clearances need to be adjusted. This is a very common symptom on the Leader engines.

OP hcurran UTC details Hooked GTS 300 Super '16, (GTS 125 Super written off in Jan 2022 - a 'SMIDSY' incident). Previously a GT125L and an ET4 Joined: UTC Posts: 105 Location: Cheltenham, UK
OP hcurran Hooked GTS 300 Super '16, (GTS 125 Super written off in Jan 2022 - a 'SMIDSY' incident). Previously a GT125L and an ET4 Joined: UTC Posts: 105 Location: Cheltenham, UK	UTC quote jimc wrote: Almost certainly your valve clearances need to be adjusted. This is a very common symptom on the Leader engines. Hi Thanks for the idea but I dont think that's it - it had a (reported) flat spot before I got it and I then did the valves with the engine out - i.e. done carefully with plenty of space to do the job well etc! BW Hugh

jimc UTC details Moderaptor The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300 Joined: UTC Posts: 44337 Location: Pleasant Hill, CA
jimc Moderaptor The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300 Joined: UTC Posts: 44337 Location: Pleasant Hill, CA	UTC quote Seriously, check them again! Slightly loose is better than ever-so-slightly tight, even if they make a bit more noise.

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