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Discussion Starter #1
Hey guys so I hope I put this post in the right place. Anyways I picked up a 02 Gsxr 750 about a month ago for a good deal, kid said it needed a tune up and it seemed to ride good so I bought it. I soon discovered it wouldn’t go over 100mph and falls flat above 5-6k rpms. So I put new plugs in, didn’t fix.
Next I took out the fuel pump assembly and cleaned the pre filter, was a little dirty but not too bad, put it all back togeather and started it up and it idles smooth but now when I give it gas it bogs bad and wants to die. So I bought a new quantum fuel pump and installed and put all back togeather and still have same problem.
Did a fuel flow test and got 950ml in 30 seconds so that didn’t seem to far off from normal of 1200ml I think it is. I have a New fuel pressure Regulator that will be here tomorrow but I do if that’s gonna fix it. Really beating my head against the wall with this bike and all I want to do is ride. PLEASE if anybody has any ideas or anything I could check would be great.
oh yeah and I put it in dealer mode and no codes are thrown and I no FI lights are on either.
Are my injectors clogged? Haven’t checked those check. Any help would be greatly appreciated! Thanks
 

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SuperMod of the North
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Injectors could be a problem. Try running a tank of Seafoam through it. With a used bike it is not a bad idea.
 

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Welcome. This is a better tech question.

You did a fuel volume test which is perfect but have you checked the pressure? A damaged or misinstalled o-ring on the pump or regulator will give you plenty of volume but the pressure will be low.
 

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If your bike goes up to 100 then stops it is most likely your STVA ( I have the same bike and went through 6 STVAs, and 1 on my old 2011 GSXR 1000 ). I would pull the top of the airbox off and make sure the top butterflies cycle front to back then cock open when you cycle the key). If it makes a strange clicking noise/noises its probably bad. Get some safety wire or zip tie and tie them open about 25% (just before your idle increases) or tie them open and lower your idle. Unplug just the servo motor wire (not the TPS) then take it for a ride and see if you can go above 100.

Clogged injectors - doubt it considering it does fine until 100 (I have 16 injectors for this bike and none of them failed)
Plugs and fuel pump - ruled out
Kinked fuel line - still possible, did you make sure to feed it smoothly below the tank as you lowered it?
FPS - 42-43 psi constant is what you want
TPS - possibly but rule out the STVA first
 

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Discussion Starter #5
Awesome hey thx for all your help guys. So UPDATE: my fuel pressure regulator arrived and I installed it and now the bike is starting and running ten times better, so I have fuel
Pressure again! Yay! But it’s still not right, it seems like it has good pickup and power when I take off but the second it gets up too 5-6k rpms it bogs out bad and falls flat.
I put a new battery in as well today and ruled that out. I haven’t done they High pressure fuel filter mod yet tho, planning on doin it tomorrow. Would that cause the bike to not wanna break 5k rpms?
As far as the stva goes the kid that had my bike before me removed all of the secondary butterflies so I don’t believe that’s the issue. I’m really thinking HPF filter but could it be that easy? Seems like it has to be that or injectors but like EVL 750 said I don’t feel like it’s injectors cuz it runs great up until 5k rpms unless it’s trying to switch over to the secondary injectors and there stopped up or something... The tps sensor is in the correct postion On the display, (the dash is in the middle) but is it possible it’s going bad and that’s why the bike bogs bad at 5k rpms?
Sorry for the story guys.
 

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Discussion Starter #6 (Edited)
Oh btw thx everyone for all of the great info.. I did actually run a can a sea foam Through the bike about 2 weeks ago and then I ran another tank through it again last week, helped a little I think. Also have been very careful when lowering the fuel tank and following the fuel line down with my hand as I close the tank to make sure it’s not kinking.. But the more I think about it the More I’m thinking either my TPS is going bad like EVL said or HPF is stopped up. Don’t have any problem with Keeping the TPS Lined up in position tho and I have heard when it’s going bad a symptom of that is you have to keep re-positioning it to be in the middle, But also couldn’t I switch it with the STPS? Cuz it’s not even being used atm, only thing with that is I know they are spring loaded so not sure exactly how they go back on there..
 

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During the times you had the pump out, did you not back flush the high pressure filter? Be gentle with it as it pleated paper inside.

From a troubleshooting standpoint, a final fuel flow and pressure check when you get everything back together can eliminate the fuel pump/filters as the issue. Troubleshooting is usually a process of eliminating the possibilities till you get to the problem.
 

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Discussion Starter #8
Ok great thx for the info, naw I never did backflush the hpf, im gonna go pull it apart here shortly and see if I can eliminate it as a possibility..
 

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Does this bike have an exhaust valve (EXVA) controlled by a servo? Could the valve be stuck closed or servo not working?

Just throwing an idea out there...
 

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Discussion Starter #10
Well update! I did the HPF bypass mod and wow! Feels like my bike just gained 50hp! It’s running amazing now from 0-85 mph but when it gets to around 85 it doesn’t want to go anymore. Could my secondary injectors possibly be stopped up? I have a full exhaust system on the bike headers and pipes and the set valve has been removed obviously but I don’t think this bike has any other exhaust valves other than in the engine and my secondary butterfly’s have been removed so pretty sure the servo motor on the bike is not doing anything.
 

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If you are satisfied with the fuel pressure and flow, the secondaries would be a logical next step.

What does it feel like when it gets around 85? Does the power go away smoothly, rough or something else?
 

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SuperMod of the North
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Well update! I did the HPF bypass mod and wow! Feels like my bike just gained 50hp! It’s running amazing now from 0-85 mph but when it gets to around 85 it doesn’t want to go anymore. Could my secondary injectors possibly be stopped up? I have a full exhaust system on the bike headers and pipes and the set valve has been removed obviously but I don’t think this bike has any other exhaust valves other than in the engine and my secondary butterfly’s have been removed so pretty sure the servo motor on the bike is not doing anything.
NO. The butterfly and servo he is referring to is in the exhaust. Should be right at the end of the header collector under the bike.
 

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Discussion Starter #16
Hey guys so bike is still running the same but I have something new happening now, it’s stopped charging my battery a few days ago and I had to buy a battery tender so I guess my stator or rectifier is out now lol great.. but as far as only going 85mph what it is is it only revs to like 6k - 7k rpms under load, it runs so strong up until 6 or 7k rpms but when it gets there it just like Boggs out and won’t go past it so in turn when I’m in the final gear it pegs at 7k rpms and just won’t go past it.... I’m sure the stator is playing a small role in this problem but I actually had the problem before it went out ... I haven’t had any compression tests done yet, it just feels so strong in the low range I don’t feel like that’s the problem, I’m really not wanting to take it to the stealership becuz no telling what crazy amount they will charge me..: oh and yes it’s a 2002 and it does have 8 injectors (I’m pretty sure) I read online that the secondary injectors don’t open till after 7k rpms so that leads me to believe they could be an issue... and as far as the butterflies and servo motor I was talking about the secondary butterflies right under the air box and I was talking about the set valve in the exhaust being removed... also it dosent have a PC or anything, I wonder if that could be a problem to since the bike has the full yosh headers and exhaust, wonder if the fuel maps could be messed up? ... any other suggestions guys Would be very helpful, I’m totally willing to send somebody some money if they figure it out or offer a suggestion that fixes it, thx for the great info everyone and God Bless Gonna try to throw new stator and rectifier on it this weekend
 

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1. Your bike does NOT have 2 sets of injectors...

2. Your bike does NOT have a Exhaust Butterfly...

Are you sure you have a 2002?

Are you sure the top butterfly's are removed? Have you physically layed eyes on it, and when you turn the throttle you can see the 1 lower set open?

3. The stator will not limit your power in specific rpms, so you have another problem going on. You can test the stator and rectifier with a volt meter and some instructional videos.

If you need a stator or rectifier I have 2 stators (both OEM and 1 brand new still in the box) for the 2001-2003 Models and 2 rectifiers. Send me money via PayPal and Ill ship them to you.

4. A power commander, Bazzaz, tune etc will not fix your rpm limitation.

You problem is most likely something other than fuel, because you cannot go past a specific rev range in every gear which is why I suspected the butterfly's. Its possible your ECU could be the problem also.

I also have a spare if you want to purchase that (I basically have duplicates of everything for this bike from trouble shooting my own).
 

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Discussion Starter #18
Hey thx for the reply EVL, yes I have physically laid eyes on the butterflies, I took the airbox off a while back to do some work to the bike and I noticed the top butterflies were missing and it only had the one lower set... well I actually just ordered new stator and rectifier off of amazon last night.. could be Ecu tho, that’s a great suggestion, hadn’t that about that, you know I accidentally reversed two of the wires on the fuel pump by accident when I put the new one in and started the bike like that, whoops, lol then I realized what I did and immediately switched it back, you think that could of messed the ecu up? How much would you need for your ecu? And yes it says on the tag on the bike and the title that it’s 2002 lol
 

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Getting the wiring wrong will only affect the fuel pump not the ECU, and honestly I doubt if its the ECU.

Did you ensure that your butterfly's fully open when twisting the throttle (based on the fact that it had been messed with)?

Was it a Rick's stator and rec? I'm pretty sure the advocates on here will tell you everything other than Ricks or OEM will be a waste of time or money.

If everything else gets ruled out I will get you a shipped price for my spare ecu.

Is the bike hard to start? Other than the normal 2002 750 hard to start.... those bikes from brand new never wanted to fire up immediately. Does it sound like all cylinders are firing smoothly?

Did you check to make sure your TPS is in the correct position and is your STPS still hooked up even without butterfly's?

Reason I asked if you owned a 2002 was because of the injector and EXUP comments which were incorrect.
 

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I know it's simple, the air cleaner is clean, right?
 
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