Vintage Vespa Forum

1974 V90 with some issues?

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SirManley RJ Manley
St. Louis, MO, USA   USA
I have had this bike for a few years now and it has some quirks. Can anyone tell me if they are normal? I did convert this bike to a battery-less harness. I don't have a voltage reg but think I need to add one.

1) The bike will not bump start. The bike does drag when in gear and rolling but it never even tries to start?

2) Seems like the points ALWAYS need adjusting. I have to set the gap set WAY too tight to get the bike to run right. When it works the bike starts with one little kick and runs well. The points are not rounded and look good. However, after a couple of weeks the bike gets harder and harder to start. More and more kicking. I check the plug and spark and they look good. More kicking and BAM she starts working. Adjusting the points, or at least fiddling with them and back to working smooth again.

3) Bike looses compression sometimes. Sometimes when kicking the bike it almost feels like the plug is out. If I bounce the bike a few times compression comes back. I just recently filled the cylinder with Marvel oil and let it sit for a day. I was thinking if the ring was dirty this would clear it up. I have had luck with this on motorcycles from the 70's. I have not had the issue since but have only ridden about 5 miles.

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dudley1972 Avatar
dudley1972 Jason C
Gillingham, Kent, UK   GBR
1962 Vespa VBB Standard 150 "Maria"
1963 Lambretta Li 150 Series 2 "Rallymaster"
Hello Mr. Manley,
Maybe the head gasket needs replacing if it looses compression, also check you hav the correct spark plug fitted, I believe Haynes does a manual for these, I would start there and get yourself a manual as it will help you to find the faults and rectify them. Another problem may be the condensor if you are running on points these tend to go and your spark will be intermitent if these need replacing.

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