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Jeff Policky
Jeff Policky, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 2425
Experience:  Yamaha Gold, Suzuki Gold, Honda Bronze, Polaris Bronze, BRP
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50cc Lambretta scooter will not start. Load test on battery,

Customer Question

50cc Lambretta scooter will not start. Load test on battery, sat. Continuity on "start switch" at NO start relay, sat. When starter leads at relay are jumped the starter spins. Replaced starter relay with no change. I'm stumped.
Submitted: 1 year ago.
Category: Motorcycle
Expert:  gomi_otaku replied 1 year ago.

Your kill switch is not tripped?

Customer: replied 1 year ago.
No, I wish.
Expert:  gomi_otaku replied 1 year ago.

When you jump the starter, will the engine start and run? Can you kick start it, and it will stay running? You are just missing the starter circuit? DO you have any aftermarket electrical parts that tie into the ecm, like a CDI box for tuning?

Customer: replied 1 year ago.
When I jump the starter, the motor turns over but does not start. Cannot kick-start. Checked fuse to starter relay. Checked continuity at start switch and kill/run switch. Cannot find wiring to brake/safety switch for starter or figure out how that is wired into the starting circuit. No add-on electronics. Completely stock.
Expert:  gomi_otaku replied 1 year ago.

Have you checked to see if your fuel pump operates when you cycle the key? And have you checked for spark at the plug when cranking? My first impulse is that your ECM has failed internally., but best to check other functions to see if they operate.

Customer: replied 1 year ago.
I have not not checked for spark. Will do that as soon as I find a spare set of hands of a test light. I did not put much thought into the fuel pump seeing as it is mechanical and does not operate unless the engine is moving.
Are there diagnostics or any overload protection for the ECM?
Expert:  gomi_otaku replied 1 year ago.

There should be a set of fuses right at the battery, the positive feed from the battery should go straight into the fuse strip

Customer: replied 1 year ago.
There is only one fuse and it is on the control side of the starter relay. It tests good. Removed relay and applied 12VDC on test bench, switch operates as it should. Checked connections at ignition tumbler. No spark at plug when key is on/run switch on and started jumped at relay.