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Discussion Starter · #1 ·
I bought a 1986 Honda trx350 a while back not running, guy said it needed a fuel cut relay, while looking the bike over when I got it home I noticed a few more things wrong, such as:
The carb was full of saw dust
The valves were way to tight
The wiring harness had be hacked in multiple spots aswell as chewed by mice, I took it all out and re wired everything with any sort of damage, cleaned all the electrical connections, and re wrapped it
It did infact need a new relay

Now that it’s all back together sometimes it starts and sometimes it doesn’t get power to the fuel pump and spark plug(happens at the same time) the only way I can get around it to start the bike is pulling the hose from the fuel pump or pulling the spark plug and switching the key on and off and hitting the start till either fuel comes flying out the pump or the spark plug sparks, after it does that once I can put it back and start it right up, does anyone know why that might be?ANY info would be greatly appreciated. Thanks
 

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I will presume it is a TRX350D (because that is the only model I have the wiring diagram for)

4811


Green is ground - fuel pump gets power from the blk/blu wire - blk/blu gets power from blk/grn (5 amp fuse) - the fuel pump relay closes when the CDI unit provides 12v on the blk/yel wire - it's most like a faulty connection at the CDI unit since it has no spark at the same time as the fuel pump fails to run. Test by jumping 12v to the blk/yel wire - if the relay closes and the pump runs and the engine starts, then immediately remove the jumper - if the fuel pump stops and spark goes away repair the faulty connection where ever it might be.
 

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Discussion Starter · #3 ·
I will presume it is a TRX350D (because that is the only model I have the wiring diagram for)

View attachment 4811

Green is ground - fuel pump gets power from the blk/blu wire - blk/blu gets power from blk/grn (5 amp fuse) - the fuel pump relay closes when the CDI unit provides 12v on the blk/yel wire - it's most like a faulty connection at the CDI unit since it has no spark at the same time as the fuel pump fails to run. Test by jumping 12v to the blk/yel wire - if the relay closes and the pump runs and the engine starts, then immediately remove the jumper - if the fuel pump stops and spark goes away repair the faulty connection where ever it might be.
It’s not the same, but I used what you told me and put the spare CDI box I had on. Now it gets fuel and spark so you were right either way, Thank you for the idea it lead to the solution in the end
 
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