Motorcycle Repair: 4 Stroke Engine Noises, piaggio lt150, vespa sprint

Question
Hey Mark, I realize you probably don't work on Vespas but I'm trying to find some basic causes for engine/transmission noises on a 150cc 4 Stroke. If you can help, great, if not I understand.

Overall the Vespa Piaggio LT150 seems to be working fine (power, etc...) but when the engine revs down to idle there is a knocking/rattle sound coming from the transmission and the exhaust sputters and gives what sounds like a small backfire. If you hold the brake and rev the engine however, the symptoms do not appear. Also of note, the engine tends to stall when cold starting. Don't know if that's relevant.

Any help would be greatly appreciated as I don't want to damage the bike before I could get it to a shop.

Thanks,

Rob  

Answer
Hi Rob,

Try the apropriate link to view service manuals Vespa.


Vespa Piaggio Service Manuals;


Cia / Bravo /Si Service Manual

http://www.mopedriders.org/html/manuals/piaggio/sm/piaggiosism.htm


Sprint

http://www.classic-vespas.com/documents/OwnersManual/Vespa-Sprint-0ps-Maint-Manu...


90 (V9A1T) Owner's Manual

http://www.scooterhelp.com/manuals/V9A1Tmanual/V9A1T.manual.r.pdf


150 Sprint (VLB1T) Owner's Manual

http://www.scooterhelp.com/manuals/VLB1T.manual/VLB1T.manual.r.pdf


Primavera (VMA2T) Owner's Manual

http://www.scooterhelp.com/manuals/VMA2T.manual/VMA2T.manual.r.pdf


P125 ETS (VSM1T) Owner's Manual

http://www.scooterhelp.com/manuals/VSM1T.manual/VMS1T.manual.pdf


125 Super (VNC1T) & Vespa 150 Super (VBC1T) Owner's Manual

http://www.scooterhelp.com/manuals/VBC1T.VNC1T.manual/VBC1T.VNC1T.manual.pdf


P125X (VNX1T)& P200E (VSX1T) Owner's Manual

http://www.scooterhelp.com/manuals/VSX1T.manual/p200.owner.pdf


150 (VBA) Owner's Manual

http://www.scooterhelp.com/manuals/VBA1T.manual/VBA1T.manual.r.pdf


GS150 (VS1T) Owner's Manual

http://www.scooterhelp.com/manuals/VS1T.VS5T.manual/VS1T.VS5T.manual.r.pdf


150 Sprint (VLB1T) Owner's Manual

http://www.scooterhelp.com/manuals/VLB1T.manual/VLB1T.manual.r.pdf


Super Sport 180 (VSC1T) Owner's Manual

http://www.scooterhelp.com/manuals/VSC1T.owner.manual/VSC1T.manual.r.pdf


P125X (VNX1T)& P200E (VSX1T) Owner's Manual

http://www.scooterhelp.com/manuals/VSX1T.manual/p200.owner.pdf



Respectfully,
Mark Shively