this is my first message… Compliments for the forum!
I need your help for a problem I have with SIP HP4 flywheel for ET3.
I have a Vespa Primavera (no ET3) with Polini 130 and Zirri Silent exhaust. Last year I changed the original ignition with the electronic ignition of ET3 (I replaced stator place, flywheel and ignition unit).
As the original ET3 flywhell is too heavy, I decided to buy from SIP the HP4 flywheel, that I received yesterday. I mounted it by simply replacing the ET3 flywheel, but it does not work properly.
The motor works very well till 6000/6500 rpm, then starts to backfire and I cannot gain more speed. It seems to be an electric problem, I tried to adjust carburation but nothing changes.
Please consider that with original ET3 flywheel I can reach at least 8500 rpm.
Is there something I missed? Reading SIP website I understood that you simply had to replace flywheel, and nothing else… Is it true?
Please help me, I spent a lot of money and my Vespa does not work!
Thank you very much for your cooperation!