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Posted

New starter recently fitted.  Old starter suffered broken field magnets.  Now will not start.  Good spark, New plug. Sparks well with second plug shorted to chassis, and new plug in place.  Loud backfire after twelve cranks or so.  Exhaust pipe smells of petrol.  Ignition switch fine. Press button start. Choke makes no difference.

Advice please.

Posted

So was it going ok before the new starter was fitted ? Do you have any ideas about how the magnets broke ?  How long has it been siting since the last run ?

Have you looked around near where you were working on the starter looking for disturbed wires/plugs or knocked off vacuum hoses ?

Are you sure the fuel is fresh ? Do you have a timing light to check the ignition timing ?

 

Posted

Thank you, was going fine before the new starter was fitted.  It appears one of the magnets became unstuck and was ground up by the armature.  Tried to start it one day and all it would do was click the relay. Not sure how to test it with a timing light, seems a good line of enquiry.  1ml of new petrol squirted into the plug hole has no effect. usually will produce a firing. Unaware of any vacuum hoses. only cabling was an earth wire to the starter ( as well as the live wire).

Posted

The load backfire makes me thing the timing is out, which could be caused by dirt or water in a plug down near the engine where the stator wires come out. Is the backfire out of the exhaust or the inlet ? If it's the inlet then it suggests a weak mixture. Exhaust it could be an intermittent spark or a mistimed spark.. I'd have a good look at the plug where the stator wires come out for intermittent connections down there(just because it's likely near where you were working).

It must presumably be getting fuel for the exhaust to smell of it.

Did you work on anything else while diagnosing the starter ? Efi systems depend on the crank and air flow sensors, and those sensors don't read very accurately at cranking speeds or voltages, so they generally feed a signal into the control unit telling it that it's being cranked. That signal is meant to fix the mixture and timing at  figures that will make it start. If the efi isn't getting the start signal the timing and mixture could be all over the place. It would be a good idea to get a manual and check the start signal is getting into the efi control unit. The efi also will have several power in wires, and several earths, you should check all the earths on the bike and the several power in wires to the efi are all good.

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