2008 Honda TRX420fm won't fire.

[gareth.campbell 0]

I have a 2011 Honda trx420fm that will not fire. It turns over fine and the fuel pump kicks in when the ignition is turned on, the lights on the display operate as they should. I have power at the coil constantly but no negative and no spark (new spark plug). I have replaced the ECU and the fuel pump relay and the engine stop relay. I did get it going a few weeks ago and it was running fine once I bridged the crank position sensor. Now it wont start at all even with engine start spray. Any advise would be much appreciated.

[Fishfiles 20,145]

Welcome to the forum , Let's see if we can get someone more familiar with the 420  @jeepwm69 @retro @toodeep @shadetree

[jeepwm69 7,619]

On 6/30/2023 at 5:41 PM, gareth.campbell said:

I have a 2011 Honda trx420fm that will not fire. It turns over fine and the fuel pump kicks in when the ignition is turned on, the lights on the display operate as they should. I have power at the coil constantly but no negative and no spark (new spark plug). I have replaced the ECU and the fuel pump relay and the engine stop relay. I did get it going a few weeks ago and it was running fine once I bridged the crank position sensor. Now it wont start at all even with engine start spray. Any advise would be much appreciated.

 

No spark then.  Normally I'd tell you to try the jumper wire from battery + to the red/black wire on the coil, but sounds like you've already got power there, which means it is NOT the fuel injection relay or rollover sensor.

 

What exactly did you do to "bridge" the crank position sensor? 

 

@Melatv walked me through most of the 420 problems I've had.  I had my fill of them and went back to the carb'd machines.

[Fishfiles 20,145]

He  mentioned no ground at the coil !!! Is the 420 the one that loses ground to the coil if the brake light sensors is bad or disconnected ? If so then disconnect the wires 

[gareth.campbell 0]

On 7/4/2023 at 8:13 AM, jeepwm69 said:

 

No spark then.  Normally I'd tell you to try the jumper wire from battery + to the red/black wire on the coil, but sounds like you've already got power there, which means it is NOT the fuel injection relay or rollover sensor.

 

What exactly did you do to "bridge" the crank position sensor? 

 

@Melatv walked me through most of the 420 problems I've had.  I had my fill of them and went back to the carb'd machines.

I bridged the crank position sensor with a piece of wire. The first time I bridged it the bike started straight away. But now I'm have no luck at all. The brake switch seems to be ok as far as i know. If you put the bike in gear and pull the brake leaver the bike will crank over but not start.

[shadetree 5,884]

try removing the ground wire from harness near the coil, sand it down, bolt it back on. check all ground wires from harness to frame and make sure they are getting a good clean connection. make sure neutral light is lit up when key is turn on ?. make sure '' kill switch '' is centered ? ( yes..most of us has been there, done that ).

[gareth.campbell 0]

19 hours ago, shadetree said:

try removing the ground wire from harness near the coil, sand it down, bolt it back on. check all ground wires from harness to frame and make sure they are getting a good clean connection. make sure neutral light is lit up when key is turn on ?. make sure '' kill switch '' is centered ? ( yes..most of us has been there, done that ).

All the ground connections have been cleaned up and continuity checked. The kill switch is in the center ans the neutral light is on. 

[shadetree 5,884]

4 hours ago, gareth.campbell said:

All the ground connections have been cleaned up and continuity checked. The kill switch is in the center ans the neutral light is on. 

bad c.d.i , bad stator ?, or bad reg/rec ?. bad ignition switch ?.