Engine falls flat on its face
HDF Community Team
Joined: Nov 2012
Posts: 6,186
Likes: 2,412
From: USA
Again, how low on gas are you when this happens?
Consider. The tank bottom is flat. If you are low on gas and accelerate hard, the gasoline gathers at the back of the tank, away from the fuel pickup. Within a few seconds, the engine will die from fuel starvation. It will quickly recover as the gasoline now rolls forward, recovering the fuel pickup.
It's the same problem as braking on a low tank, and the engine dying as you stop, but immediately restarting.
Not claiming this is the problem, but the symptoms may match.
Consider. The tank bottom is flat. If you are low on gas and accelerate hard, the gasoline gathers at the back of the tank, away from the fuel pickup. Within a few seconds, the engine will die from fuel starvation. It will quickly recover as the gasoline now rolls forward, recovering the fuel pickup.
It's the same problem as braking on a low tank, and the engine dying as you stop, but immediately restarting.
Not claiming this is the problem, but the symptoms may match.
Thread Starter
|
Road Captain
Joined: Dec 2009
Posts: 512
Likes: 6
From: Minnesota
Again, how low on gas are you when this happens?
Consider. The tank bottom is flat. If you are low on gas and accelerate hard, the gasoline gathers at the back of the tank, away from the fuel pickup. Within a few seconds, the engine will die from fuel starvation. It will quickly recover as the gasoline now rolls forward, recovering the fuel pickup.
It's the same problem as braking on a low tank, and the engine dying as you stop, but immediately restarting.
Not claiming this is the problem, but the symptoms may match.
Consider. The tank bottom is flat. If you are low on gas and accelerate hard, the gasoline gathers at the back of the tank, away from the fuel pickup. Within a few seconds, the engine will die from fuel starvation. It will quickly recover as the gasoline now rolls forward, recovering the fuel pickup.
It's the same problem as braking on a low tank, and the engine dying as you stop, but immediately restarting.
Not claiming this is the problem, but the symptoms may match.
Road Warrior
Joined: Nov 2007
Posts: 1,800
Likes: 307
From: Houston, Texas
Someone else mentioned that you should talk to who ever tuned your bike. I'm no expert by any means so of course this may not be your problem but I have read that when you go wide open on the twist grip, the computer will hold the throttle plate about half until the engine catches up enough to let it open all the way. This keeps the velocity of the intake air up so that it fills your cylinders better for better acceleration. If the throttle plate goes wide up right off the bat, velocity drops to nothing and it will fall out until it catches up. Try twisting the throttle as you accelerate instead of slamming it and see if your times improve and the engine keeps up.
Just thought I'd give you one more possibility to stress over
Good luck.
Just thought I'd give you one more possibility to stress over
Good luck.
HDF Community Team
Joined: Nov 2012
Posts: 6,186
Likes: 2,412
From: USA
OK. That pretty well takes out the possibility of it sucking dry at the pickup point.
Let me make sure I'm understanding the symptoms.
It's *not* falling flat every time you hit a particular RPM. It's only happened a few times (about a dozen times), and it's only after you've been on it for a few seconds, about the time you hit 4th gear. Do I have that right?
Lastly, it recovers very quicky. You said, "When I let up and throttle again then I can go again." Is that is essentially instantaneous as that sounds, or is there a second or two there before it recovers?
Basically, to me, it still sounds like a fuel starvation problem. I'd be happier as far as a diagnosis goes if it did it every time.
While the pickup point may not be being uncovered, a cracked fuel line might be. It wouldn't be a problem as long as the crack is under the gasoline level, nor would it be a problem if it's a small crack and the fuel pump is able to keep up with the demand (though you might have some roughness or such, especially when low on fuel and vacuum is maximized). The problem could be overwhelmed though under a sustained high load though, like drag racing.
Let me make sure I'm understanding the symptoms.
It's *not* falling flat every time you hit a particular RPM. It's only happened a few times (about a dozen times), and it's only after you've been on it for a few seconds, about the time you hit 4th gear. Do I have that right?
Lastly, it recovers very quicky. You said, "When I let up and throttle again then I can go again." Is that is essentially instantaneous as that sounds, or is there a second or two there before it recovers?
Basically, to me, it still sounds like a fuel starvation problem. I'd be happier as far as a diagnosis goes if it did it every time.
While the pickup point may not be being uncovered, a cracked fuel line might be. It wouldn't be a problem as long as the crack is under the gasoline level, nor would it be a problem if it's a small crack and the fuel pump is able to keep up with the demand (though you might have some roughness or such, especially when low on fuel and vacuum is maximized). The problem could be overwhelmed though under a sustained high load though, like drag racing.
Thread Starter
|
Road Captain
Joined: Dec 2009
Posts: 512
Likes: 6
From: Minnesota
OK. That pretty well takes out the possibility of it sucking dry at the pickup point.
Let me make sure I'm understanding the symptoms.
It's *not* falling flat every time you hit a particular RPM. It's only happened a few times (about a dozen times), and it's only after you've been on it for a few seconds, about the time you hit 4th gear. Do I have that right?
Lastly, it recovers very quicky. You said, "When I let up and throttle again then I can go again." Is that is essentially instantaneous as that sounds, or is there a second or two there before it recovers?
Basically, to me, it still sounds like a fuel starvation problem. I'd be happier as far as a diagnosis goes if it did it every time.
While the pickup point may not be being uncovered, a cracked fuel line might be. It wouldn't be a problem as long as the crack is under the gasoline level, nor would it be a problem if it's a small crack and the fuel pump is able to keep up with the demand (though you might have some roughness or such, especially when low on fuel and vacuum is maximized). The problem could be overwhelmed though under a sustained high load though, like drag racing.
Let me make sure I'm understanding the symptoms.
It's *not* falling flat every time you hit a particular RPM. It's only happened a few times (about a dozen times), and it's only after you've been on it for a few seconds, about the time you hit 4th gear. Do I have that right?
Lastly, it recovers very quicky. You said, "When I let up and throttle again then I can go again." Is that is essentially instantaneous as that sounds, or is there a second or two there before it recovers?
Basically, to me, it still sounds like a fuel starvation problem. I'd be happier as far as a diagnosis goes if it did it every time.
While the pickup point may not be being uncovered, a cracked fuel line might be. It wouldn't be a problem as long as the crack is under the gasoline level, nor would it be a problem if it's a small crack and the fuel pump is able to keep up with the demand (though you might have some roughness or such, especially when low on fuel and vacuum is maximized). The problem could be overwhelmed though under a sustained high load though, like drag racing.
Thread Starter
|
Road Captain
Joined: Dec 2009
Posts: 512
Likes: 6
From: Minnesota
I did call Fuelmoto haven't heard back yet.
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Thread Starter
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Road Captain
Joined: Dec 2009
Posts: 512
Likes: 6
From: Minnesota
Someone else mentioned that you should talk to who ever tuned your bike. I'm no expert by any means so of course this may not be your problem but I have read that when you go wide open on the twist grip, the computer will hold the throttle plate about half until the engine catches up enough to let it open all the way. This keeps the velocity of the intake air up so that it fills your cylinders better for better acceleration. If the throttle plate goes wide up right off the bat, velocity drops to nothing and it will fall out until it catches up. Try twisting the throttle as you accelerate instead of slamming it and see if your times improve and the engine keeps up.
Just thought I'd give you one more possibility to stress over
Good luck.
Just thought I'd give you one more possibility to stress over
Good luck.
HDF Community Team
Joined: Nov 2012
Posts: 6,186
Likes: 2,412
From: USA
It doesn't do it at a certain RPM, it is usually right after shifting. I can shift through the gears as long as I'm not full throttle. When I race through the gears is the only time it does it usually 4th gear (possibly 3rd gear too). I can roll on in any gear and have no problems. As far as how long it recovers, its not instant but about 1 or 2 seconds. Only happens when racing.
Remember, when you're racing the engine is spinning up around redline and the throttle is wide open. So you are maximizing fuel throughput. Simply rolling on the throttle does not do this. Nor does holding the throttle open at a lower rpm. Wide open throttle at 1/2 of redline is 1/2 the fuel usage at redline.
That said, I'm suspicious of the relationship to shifting. I can't explain that from a fuel supply perspective. Though depending on the engine mapping/software, a sustained over-rev or extreme over-rev may be mapped as a shut down. Kinda doubt it though. Usually you just rapidly bounce of the rev limiter.