I've been dealing with an issue on my Honda Montesa where the bike cranks over but won't start. It has spark and engine compression, but I found the fuel tank and injector were full of sand, so I cleaned them out. The bike ran for a few seconds and then died. Even after cleaning, it still won't start, and the fuel pressure is within specifications. I noticed that the charging system voltage is extremely low and showing spikes of negative voltage when I viewed the first two charging system waveforms. The stator output is strong and within spec. I tried removing the charging system capacitor and replacing it with a small 12-volt battery, but the bike still won't start. Any ideas on what could be causing this issue with the charging system and not running?

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Good morning,

I think the thing to do is back up and take another wide angle look at this situation.

Tell us more about this bike. What model is it specifically?
I found this website with info https://www.montesa.com/en/manuals/

I took a look at the 20/20 Montesa 4Ride Shop manual.

If you have compression and spark the engine should run on an alternate fuel source like carb spray or brake clean.

If the engine does run on an alternate fuel source the next logical step is to verify there is a command from the ECM to the injector to open it.

If there is a command we can make the call that this is a fuel flow related issue and not a ECM or RPM input issue.


Try running the engine on an alternate fuel source. We don't need it to run for minutes or hours just a few seconds will do.

Make a capture of the fuel injector(s). We need to see supply voltage, the control from ECM and in an ideal world we would like to know the current flow through the injectors and some sort of crank position signal.

After looking at the capture I can't come to any conclusions.

I need to know more about where your connections were made and what was happening at the time. The noise you saw just looks like noise to me.

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