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Discussion Starter #1
I have tried to do some research but I have not been able to narrow down my problem. Maybe you guys can give me some advice.

History:

Had this bike for about a year. It was bone stock, all mods done by me. Relevant mods: full system, velocity stacks and quick throttle (all done recently). Bike has fresh fuel, a clean air filter and chain. Battery is strong and the bike has only 3500 miles on it (I know, I bought it with half of that a year ago). I have not let it sit without fuel stabilizer or being run every couple weeks.

After the last of the mods were done I took the bike to Apex Moto, in Anaheim, to get the bike tuned. Power curve came out smooth. A/F mixture is clean except for a small dip at about 10k RPM. See attached.



Problem:


As I was riding home I noticed that under full acceleration the bike would loose some power at about 11-12K RPM and then pick back up. It only happened about once or twice on the fwy and I didn't think too much of it since one of the throttle cable housings were broken. I was thinking the cable was sticking.

Since the tune I lifter the tank, air box and replaced the throttle cables. Install went fine. Started right up as before. Took the bike to Buttonwillow this last weekend and thats where I really started noticing the problem. Under any heavy acceleration the bike will loose power around 12K RPM. It happened almost every time unless I was going gentle on the throttle (but a loss of power was still noticeable, just not as pronounced).

Troubleshooting:

I am planning on lifting the tank again and making sure I am not pinching any tubes/lines. I am pretty sure they are fine but I will check anyway.

I talked to Apex and they will take a look at the bike but he suggested that it might be the change in altitude between Anaheim and Buttonwillow. I want to beleive that but since the bike consistently dies at 12K I am thinking its not environmental.

Does anyone have any experience with this problem or any relevant suggestions? Thanks :toothy4::toothy4::toothy4:
 

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Fuel pump. Full throttle and high RPMs demand the most fuel. Your pump is either shot or filter clogged. Either are fixed with a new pump. Could be pinched lines and even a vacuum in the tank from a vent hose being pinched. But if everything looks good... then its the pump.
 

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You say that you put a full system on your ride. Do you have a Power Commander installed on your bike? With the different exhaust pressures, you will have to "Re-map" your ECM/injectors. Whenever you do a modification, if you gain in one area, you will ultimately suffer a loss somewhere else. Usually, with a full exhaust system, your Mid-range will suffer but you will gain at the top end. Since your bike was tuned (stock) from factory with an engineered system for air/fuel mixture and corrolated back pressure, you will have to re-map your FI system due to the new parts.

Once you get the power commander, bring it to a shop with a dyno and have them Re-map your system so you can gain full advantage of your full system.
 

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Discussion Starter #4
Once you get the power commander, bring it to a shop with a dyno and have them Re-map your system so you can gain full advantage of your full system.
I already had the power commander mapped (see above).

Dcope - I am hoping its simply a pinched line and not the pump. You mentioned that the filter can be fixed by replacing the pump. I assume you can also just replace the filter?
 

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I don't know if you can just change the filter. It sound stupid to say that you can't but I don't see a part number for the filter... just the pump assembly. Call a shop and see what they say about changing it.

An ebay pump isn't too expensive. I'm guessing less than $100.

What year is your bike/

There are 2 things to test on the fuel pump. Pressure and Flow. I can look up what the pressure i supposed to be. They make a tool to check the pressure but I don't know if you can fit just a tire pressure gauge to the line. Even if the fuel messes up the gauge... you only need it once.

Flow... I'd have to look it up too but you put the line in a bowl and run the pump for whatever time they say and you should have a specific amout of fuel in the bowl.
 

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Discussion Starter #6
I don't know if you can just change the filter. It sound stupid to say that you can't but I don't see a part number for the filter... just the pump assembly. Call a shop and see what they say about changing it.

An ebay pump isn't too expensive. I'm guessing less than $100.

What year is your bike/

There are 2 things to test on the fuel pump. Pressure and Flow. I can look up what the pressure i supposed to be. They make a tool to check the pressure but I don't know if you can fit just a tire pressure gauge to the line. Even if the fuel messes up the gauge... you only need it once.

Flow... I'd have to look it up too but you put the line in a bowl and run the pump for whatever time they say and you should have a specific amout of fuel in the bowl.
Thanks. I will pull out the service manual later on and do some reading. There should be a troubleshoot for the fuel pump/filter.
 

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I agree with the fuel pump diagnosis. I had a very similar problem and replaced the pump with one i bought off the forum for $50 shipped and now the problem has gone away. I highly recommend switching the pump out. As for replacing the filter- I've looked very carefully at my old pump and the filter seems to be plasti-welded to the rest of the unit. it does not look like something that's designed to be replaced or removed at all. I would recommend replacing the entire unit since units can be found relatively cheaply. This problem usually comes around at 20,000 or so miles though, so the fact that you're having the problem at such low miles, to me suggests two things:

1. the guy you bought it from replaced the gauges with lower miles
2. the fact that the bike sat so long means that there's gummed up gas in the filter

GL- it's something small- don't worry about it too much. for now- i recommend keeping the tank as full as possible. for me, the problem wouldn't manifest until i had two bars or less of fuel.
 
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Discussion Starter #8
I agree with the fuel pump diagnosis. I had a very similar problem and replaced the pump with one i bought off the forum for $50 shipped and now the problem has gone away. I highly recommend switching the pump out. As for replacing the filter- I've looked very carefully at my old pump and the filter seems to be plasti-welded to the rest of the unit. it does not look like something that's designed to be replaced or removed at all. I would recommend replacing the entire unit since units can be found relatively cheaply. This problem usually comes around at 20,000 or so miles though, so the fact that you're having the problem at such low miles, to me suggests two things:

1. the guy you bought it from replaced the gauges with lower miles
2. the fact that the bike sat so long means that there's gummed up gas in the filter

GL- it's something small- don't worry about it too much. for now- i recommend keeping the tank as full as possible. for me, the problem wouldn't manifest until i had two bars or less of fuel.
Thanks for the info. The problem occurred when the tank was full btw.

Since this wasn't my first RR, I took the whole bike apart. I am positive the bike does not have more miles than indicated on the gauge. It could be that the bike sat for a while, which I know it did. I guess the guy was not truthful about always running fuel stabilizer.

Do I have to worry about the gas gumming up in the injectors or lines? I am thinking about running some lucas injector cleaner, any reason why it would be a problem in the bike?
 

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Discussion Starter #9
UPDATE: Took the bike out for a ride the other day and there was no problem. I only ran the bike for 15 minutes but it reached operating temp and then some.

Took the tank off and checked connections/pinch in the lines and there was none.

The altitude between Buttonwillow and where I had the bike tuned is only off by 100 feet.

What could cause the bike to lose power at 12k at the track?
 

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I'd take it to the shop for a fuel pump test. I don't think you have enough fuel pressure at high RPM/ wide open throttle and it makes it run lean at those RPM's.

Hop on the bike and redline it in first gear with just enough throttle to get it to rev that high. Then hold the throttle wide open and rev to redline. Will it even make it to 15K with WOT?
 

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Discussion Starter #11
I'd take it to the shop for a fuel pump test. I don't think you have enough fuel pressure at high RPM/ wide open throttle and it makes it run lean at those RPM's.

Hop on the bike and redline it in first gear with just enough throttle to get it to rev that high. Then hold the throttle wide open and rev to redline. Will it even make it to 15K with WOT?
I will check that, I ran the bike WOT until about 13k to see if it bogged but I have not tried this technique yet. I will check it out the next time I am with the bike.
 

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In most cases I would agree that the fuel pump is the most likely cause. However, I've had a similar experience that is almost exactly as you describe. The only difference I may see is that my problem was repeatable. At 3,500 miles I wouldn't suspect a bad fuel pump they can go at anytime.

In any case, I think we all agree that this is a fuel starvation problem. My suggestion would be to see if the problem is repeatable over the next few tank fulls. If the answer is Yes, then have it remapped OR back up your current map (which you should have already) to your hard drive. Then add +10 to your fuel map between 10k-12k rpm at all throttle positions. If the problem goes away then you've proven it's a mapping problem.

If the problem goes away by itself then you could have had some trash in your gas or bad gas.

You can't replace the fuel filter but you can pull out the fuel pump and clean the fuel strainer.

You need 50psi on the fuel rail and a minimum of 6.5 US ounces in 10 seconds.
 

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Discussion Starter #13
In any case, I think we all agree that this is a fuel starvation problem. My suggestion would be to see if the problem is repeatable over the next few tank fulls. If the answer is Yes, then have it remapped OR back up your current map (which you should have already) to your hard drive. Then add +10 to your fuel map between 10k-12k rpm at all throttle positions. If the problem goes away then you've proven it's a mapping problem.
Very good idea. I would be surprised if the fuel starvation arose from the map since he told me that the bike was tuned for a healthier A/F mixture. The bike is more rich than it was going into the shop and it never cut out before.

I was concerned that the bike was running too rich though. After the shop asked me about the elevation of the track he mentioned that some people will get the engine to react similarly after reaching the top of a mountain or high canyon. With this logic, the higher you go = the less air in the atmosphere which = richer fuel mixture.
 

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That is very possible. But did he disable the PAIR valve and use a tail pipe sensor? If you do think it's too rich then try subtracting 10 from the fuel map.
 

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Discussion Starter #15
That is very possible. But did he disable the PAIR valve and use a tail pipe sensor? If you do think it's too rich then try subtracting 10 from the fuel map.
I will definitely play around with the map (after I save it of course) when I have time this weekend.

I installed PAIR plates, checked them after the tune, and I am not sure about which sensor he used. I will end up asking when I head back to the shop. They said they would diagnose the problem and from my experience they are good people. Thanks for the input, very informative. :toothy4::toothy4::toothy4:
 

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Discussion Starter #17
UPDATE: Finally had a free moment to take the bike out last night and I tried to replicated the problem. Holding the bike at high rpm and then going WOT did make it cut out again. I cannot think of anything else it could be other than the fuel pump/filter. I am going to try to get it replaced before I head back to the dyno shop and have them check it out. Any input on replacing or buying a pump would be appreciated, otherwise thanks for the help guys.

Evan
 

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Yep, low fuel pressure/flow. Bikes are parted out on ebay all the time. A fuel pump prob. isn't a fast selling item so I'd offer people less than the starting price and someone will accept it. ( I bought a crankshaft that way) (how many people are looking for a crankshaft? Almost none, so I got it for like $100.)
 

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Why not take it back to the dyno and confirm your bike is actually starving at 100% throttle position before buying parts? You're fuel pump may be fine and the map may be the problem. Especially if the problem didn't happen before the mapping. Just a thought...

PS. Did you try to add or subtract fuel at 100% throttle position? If you're worried about messing something up just use the buttons on the PCIII to raise the map in the high rpm range. Move the lights up 2 bars and try it. That's easy enough to put it back.
 

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Discussion Starter #20
Why not take it back to the dyno and confirm your bike is actually starving at 100% throttle position before buying parts? You're fuel pump may be fine and the map may be the problem. Especially if the problem didn't happen before the mapping. Just a thought...

PS. Did you try to add or subtract fuel at 100% throttle position? If you're worried about messing something up just use the buttons on the PCIII to raise the map in the high rpm range. Move the lights up 2 bars and try it. That's easy enough to put it back.
Thats what I was planning on doing but I was not able to take it to the shop this saturday so I figure ill shop around for a pump until I take it back next saturday. In any case I am going to wait for what the shop says before I start changing out parts.

I completely forgot that you could change the map without a computer! I had the chance today but only had a mac (and the PC program only works with windows). Hopefully next saturday I will have an answer. If its the map at 100% I would be concerned about the quality of the entire map...
 
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