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Discussion Starter #1
Hi again all,

I need your advice on where to start looking for the cause of this mysterious ailment. The bike is a 2001 Monster S4 with many a mile under her tyres. First off, I've consulted the forums before and replaced my fuel filter and vent hoses. When this did not remedy the problem, I eliminated the side stand switch and soddered the wires together to complete the circuit. Unfortunately this did not solve the problem either.

What happens: when I turn the key on the bike I hear the fuel pump (like normal), lights and everything illuminate and work properly (fully charged battery). When I hit the start button the engine continues to turn over and will not start. Funny thing is is that I can turn the key to the "off" position and turn it back to the "on" position and it will start just fine (95% of the time). Sometimes (4% of the time) it will backfire as it does so.

What happens while riding: As I pass into the higher rpms (7-8k) during rapid accelelation the engine suddenly cuts out and I am flung forward with the force of deceleration and nearly crap my pants. It's similar to what happens when you hit the kill switch while riding. I can flip the kill switch from "off" to "on" and it will backfire like a shotgun and restart while still rolling. If I let it come to a stop it is difficult to restart and will turn over many times before firing up.

Things I've noticed: Last nite I could hear a humming sound coming from the fuel tank cap. I openned the cap and it was not pressurized to any noticable extent. I've tried openning the cap when the bike cuts out/won't start, but it doesn't remedy the problem. I still have to turn the key off and on before starting.

Perhaps the kill switch on the handlebar is faulty? Or perhaps the ignition? Ground wire? Please help me diagnose this if you can!

thanks in advance!
 

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Ive had the first problem your describing with starting and then a host of problems when riding with a bad tank of gas. Not high enuff octane or something not sure?

If your engine is cutting during rapid acceleration it could be you've a slight problem with your internal combustion that becomes more evident under stressed conditions.

Easy checks on that are spark plugs, valve clearance and your fuel/air mix.


Hi again all,

I need your advice on where to start looking for the cause of this mysterious ailment. The bike is a 2001 Monster S4 with many a mile under her tyres. First off, I've consulted the forums before and replaced my fuel filter and vent hoses. When this did not remedy the problem, I eliminated the side stand switch and soddered the wires together to complete the circuit. Unfortunately this did not solve the problem either.

What happens: when I turn the key on the bike I hear the fuel pump (like normal), lights and everything illuminate and work properly (fully charged battery). When I hit the start button the engine continues to turn over and will not start. Funny thing is is that I can turn the key to the "off" position and turn it back to the "on" position and it will start just fine (95% of the time). Sometimes (4% of the time) it will backfire as it does so.

What happens while riding: As I pass into the higher rpms (7-8k) during rapid accelelation the engine suddenly cuts out and I am flung forward with the force of deceleration and nearly crap my pants. It's similar to what happens when you hit the kill switch while riding. I can flip the kill switch from "off" to "on" and it will backfire like a shotgun and restart while still rolling. If I let it come to a stop it is difficult to restart and will turn over many times before firing up.

Things I've noticed: Last nite I could hear a humming sound coming from the fuel tank cap. I openned the cap and it was not pressurized to any noticable extent. I've tried openning the cap when the bike cuts out/won't start, but it doesn't remedy the problem. I still have to turn the key off and on before starting.

Perhaps the kill switch on the handlebar is faulty? Or perhaps the ignition? Ground wire? Please help me diagnose this if you can!

thanks in advance!
 

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I might also suggest a fuel pump problem. Is there a power commander installed on the bike?
 

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Discussion Starter #6
Hey, Thanks for all the replies!

Plugs are good: grayish brown. No power commander is installed. The bike runs great and accelerates strong up until the point that it cuts out. Through it all I've always (for the last year or so) had to turn the key twice to get it to fire up. The fuel pump is, I believe, one of the strongest suspects. When I changed the fuel filter, therefore reducing back pressure on fuel flow (clean path to flow through), the symptoms temporarily ceased. I have a book on the bike and will check the fuel pump diagnostics.

Does this logic seem to make sense to you guys?

Keep the suggestions coming while I fettle with this pump, if you would be so kind.

Thanks again, yall!

-Andy
 
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