Today while riding I noticed leaking fuel hose, so I turned around and went home to change it ( the bike was running perfectly). I unmounted the fender and the tank, changed the fuel line and put everything back together. To my surprise it is not starting. Pulled out the plug (brick colour) and tested for spark, it had none.

Checked the killswitch but that is working fine, cleaned all connections and still nothing.

I did not touch the wiring when I changed the fuel hose.

When checking the killswitch I measured around 13.7V so I suppose the alternator is all right. 

When I put my finger on the spark plug wire end I can feel a slight tingle.

No idea why it would stop working so spontaneously. 

Please help with some ideas.

 

Also the case has no timing mark. 

Did you already read "Sherco Ignition Timing Manual Supplement" at least you can see where the timing make is suppose to be.  Personally I doubt there is a problem with the timing.  Continuity meter test of the ignition timing pickup coil would be in order, the timing pickup initiates the spark which is intensified by the ignition module and the ignition coil.  Service manual will show resistance values you should see on the wires connected to the ignition module inputs.

The rectifier/regulator should only be needed for the fan motor and possibly lights and that is the only place you should read DC power of roughly 12 volts, everything else will be AC.

Based on the photos you have some work to do on the spark plug wire and cap, everything downstream of the ignition module to the plug cap can also be meter tested for continuity.

Cut that spark plug wire 1/2 inch to some fresh wire and try again.

How old is your spark plug cap?  Service manuals indicate a short life for resistor plug caps and recommend a fairly frequent scheduled replacement.

 

10 hours ago, konrad said:

 

Lots of info there but that fella never returned to say what the problem was.

It's a rare individual who reports back.  Honestly, if more users did so, I'd be more willing to offer suggestions.

I admire your willingness to help, lemur.

Grew up around electricity and electronics, it's a passion.  

But in this case this is why I always like to buy my trials bikes in pairs, makes troubleshooting a no brainer 😆

 

Hi, sorry for not responding, was away.

We bought a pair but different makes so that is no help.

I have read the sherco lost spark thread but haven't seen the conclusion.

I have tried several spark plugs and it is not that. 

Some local electrician repair man have told me that if it's giving spark (witch it does but it is weak) it is not the CDI/Coil problem and I should check the alternator voltage. 

On 4/27/2024 at 11:22 PM, lemur said:

Service manual will show resistance values you should see on the wires connected to the ignition module inputs

Could you send me the values or the service manual, I have no leads.

Thanks for all the info.

UPDATE:

So the weak spark is actually normal for sherco. It bridges 9mm from HT cable to frame. 

I tried to pour some gas directly into the bore, installed the spark plug and kicked it over and it fired right up.

So it is an carburetion issue.

 

Thanks for all the help.