2000 gsxr 750 y bogging down - GSXR.com
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post #1 of 85 (permalink) Old 07-12-2018, 10:46 AM Thread Starter
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2000 gsxr 750 y bogging down

No check light on with svta plugged in and hooked to spec motor boggs down between 7-9000 rpm. Un hook the stva cables manually close upper butterflies and i get full throttle responce but also loose alot of power on the road f1 light of corse comes on but still reads c-00 even with stva unplugged from harness??
In the past week i put on new svta cables spark plugs ,fuel pump ,adjusted tpi (even tho it was ok) checked the bike over top and bottom checked charging system im sure ive missed some stuff ive done, i cant find any thing wrong..... the butterfly thing really has me thrown off... can some one help
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post #2 of 85 (permalink) Old 07-12-2018, 10:47 AM Thread Starter
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The stva servo cycles normal before start up
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post #3 of 85 (permalink) Old 07-12-2018, 12:14 PM Thread Starter
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Can someone please help
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post #4 of 85 (permalink) Old 07-12-2018, 07:49 PM
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@Chuckster is the STVA guru but I'm not sure on your vintage bike.

Reading your post, it is not clear to me what you are doing. I don't know how you get "full throttle response" with the secondaries closed.

Maybe you could elaborate.

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post #5 of 85 (permalink) Old 07-13-2018, 09:42 AM Thread Starter
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elaboration, my throttle bodys 4 of them have 2 butterflys each a upper and lower, the stva on my bike controlls useing a servo the upper butterflys, if i manually close and hold shut upper butterflys i get a perfect rev all the way to 14000rpm, the minute i open upper butterflys somewhere between 7-9000 rpm the throttle boggs as if its starving for gas
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post #6 of 85 (permalink) Old 07-13-2018, 11:50 AM
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Sounds to me you have a fuel issue. I would start with pressure test, and then volume test. Likely a pressure issue. Has the fuel pump ever been changed out? Bike that old likely over due for one. Also, check the filters for flow before dropping coin on a new pump. Worst case, injectors are clogged up, or just shot? Just my 2 cents...

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Last edited by Spyder13; 07-13-2018 at 11:53 AM.
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post #7 of 85 (permalink) Old 07-13-2018, 12:07 PM Thread Starter
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i just rebuilt fuel pump last week i thought u were right, i used a 50$ elctric pump filter on the old housing the results did not change i also spent nearly 45 mins cleaning the gunk out of rest of housing
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post #8 of 85 (permalink) Old 07-13-2018, 12:10 PM Thread Starter
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i changed spark plugs tested coils , adjusted tps altho it did not need it tested stator and charging system ... im trying to remember all i did i did alot checked vaccume lines fuel lines tested alot of sensors with multi meter
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post #9 of 85 (permalink) Old 07-13-2018, 12:12 PM Thread Starter
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thanks for your help spyser u could be right about injectors but if it was injectors i dont think it would rev good anytime? i think atleast leaning twords a its a sensor or electical issue but im not sure
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post #10 of 85 (permalink) Old 07-13-2018, 12:36 PM Thread Starter
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if my throttle cable qas not adjusted propperly open or close could that cause my issue?
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post #11 of 85 (permalink) Old 07-13-2018, 01:52 PM
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Well, you said if you close off the secondary butterflies it will rev normally. If I understand it correctly, the secondaries act like a choke flap. If you have to take air away to get it to run right, then you have a lack of fuel. I would be checking fuel pressure at the fuel rail. I assume there is fuel pressure regulator? I don't have any experience with the fuel injection on motorcycles. I can only assume it is at least close to the same as a car/truck system, just smaller. But, even if I knew nothing about fuel injection, I am positive, going off you symptoms, you have a lack of fuel in your air/fuel mixture... Why is the question. You adjusted the TPS, did you test it? DVOM shows that it has the full range of resistance? Do you have a high pressure fuel filter in you tank like the newer bikes?

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post #12 of 85 (permalink) Old 07-13-2018, 02:06 PM Thread Starter
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i did test tps it appears to be working correct, to my findings i have one fuel filter in the pump its brand new. i want to aggree with u it seems like a fuel issue but i went threw the system other than replace injectors , i dont know how to test them other than to tell u they are all squirting fuel. when i replaced fuel pump last week i was 100 percent positive that was the issue but it would appear i was wrong, the stva is a known issue but mine appears to be working , i found a used one for 75$ but ive invested so much time and effort money into this bike im skeptic to replace another part unless im sure its it
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post #13 of 85 (permalink) Old 07-13-2018, 02:09 PM Thread Starter
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when this issue first began i swore i had got bad gas, it was sudden and before that it ran beautifully it has about 10000 miles on bike when i replaced plugs none were fouled i thought age got them but i was wrong again
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post #14 of 85 (permalink) Old 07-13-2018, 02:13 PM
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Not much clearer but I'm guessing that you are saying that the bike will rev to redline with the secondaries held fully closed.

That would not be normally possible unless you have a big intake leak.

I suspect the rubber boots between throttle bodies and the cylinders is loose or cracked. You might also have a hose off somewhere, but it seems like it would have to be a bigger leak than that.

If a visual check does not reveal a problem, spray some WD-40 or similar around the joints and see if you get a change in the idle speed.
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post #15 of 85 (permalink) Old 07-13-2018, 06:33 PM Thread Starter
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i was thinking vacume leak after the fuel pump did not work i did try the wd40 thing around most of the motor, i can say i was so frustrated at the time i would not guarentee my test .., i will try again tom morn
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post #16 of 85 (permalink) Old 07-13-2018, 06:35 PM Thread Starter
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ty for your help and imput, anything else comes to mind please lmk
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post #17 of 85 (permalink) Old 07-13-2018, 06:38 PM Thread Starter
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i did not work on it much todAy i did start i noticed there was a little play in throttle return cable i did rev it till it was bogging and just played with return cable and it seemed as tho it was trying to rev higher but still bogging , i will look more into that tom also
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post #18 of 85 (permalink) Old 07-14-2018, 06:20 AM
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On stands, there's no load on the engine but friction and it'll easily go to the redline with the secondaries shut. But, it should also do the same with the secondaries wide open.

The difference here is going to be the air charge it can pull in. There is restriction with the secondaries closed and you're probably getting close to what the AFR should be. Open, and it's gulping in air and you probably are going super lean causing the engine to stumble.

It sounds like your STVA is working fine. Reconnect your cables and adjust it according to the manual.


Here's the rundown of how I would test:
1) Physically not delivering enough fuel. Test fuel pressure and volume delivery. TEST! Don't assume.

2) Unplug the electrical connections the IAT, AP, and IAP sensors. These three sensors are used to calculate the air density. Unplugging them will use stock values. If the bike suddenly runs right, start plugging them in one at a time, in that order. It'll code with the sensors unplugged, but you're testing for bad data.

3) Vacuum leak. A small leak in the IAP hose system will cause all kinds of goofiness. Ever have a hole in a soda straw? Same thing. Suck hard enough and you'll get some drink. Same situation here. With the secondaries closed, you're putting a lot of negative pressure on that leak. Basically, it's making the IAP have bad data and when you close the secondaries, you're altering the engine conditions to match it (possibly).

4) Vacuum leak. This is where we get into either unlucky or stupid. The idle air adjustment screws have o-rings to seal them up. If they've rotted and cracked, a leak can form. Your WD-40 test should work here. Or, they've all been backed out so far you've provided a secondary air source. Still, this wouldn't affect WOT to the redline. That's why I've put it last.
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post #19 of 85 (permalink) Old 07-14-2018, 06:25 AM Thread Starter
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ty chuckster for your help, i am going to work on it later today, all the utube vids ive watched and all the forums i read no 1 broke it down quite like that! ty ty ty
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post #20 of 85 (permalink) Old 07-14-2018, 06:51 AM Thread Starter
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does anyone know what exact psi and volume the pump should be produceing, i will try to locate guages today, i think auto zone accually has them on loan a tool... if not i hate harbor freight but id bet they would have it
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post #21 of 85 (permalink) Old 07-14-2018, 07:26 AM
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Pressure should be 43psi. Volume should be 1.3 us ounces after running the pump for 30 seconds.
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post #22 of 85 (permalink) Old 07-14-2018, 08:16 AM
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Quote:
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Pressure should be 43psi. Volume should be 1.3 us ounces after running the pump for 30 seconds.
I've seen these numbers in the older manuals but the volume can not be right.

Using the rough specific fuel consumption of a piston engine of .5 lbs of fuel / HP / hour, that equates to at least 10.4 ounces minimum in 30 seconds at 120 hp and there should always be extra delivery available so the pressure remains stable.

Later manuals use the same 43 psi pressure but go to 5.7-5.9 oz in 10 seconds or about 17 oz / 30 seconds which is right in line with what what would be expected.

Otherwise, I'd go with 43 psi minimum and at least 5.8 oz in 10 seconds or 17 in 30 seconds, no load.

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post #23 of 85 (permalink) Old 07-14-2018, 10:18 AM
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I agree. It seemed too low to me too, but that's what is in the manual. Seems way low. Sorry if I misled.



I just rechecked the book, and it's pretty confusing. It's written like this:


"Fuel discharge amount: Approx.1 200 ml/30 sec.


(1.3/1.1 US/IMP oz)/30 sec.


Note the space between the 1 and the 2. Is that 1200 ml, or 200 ml? Either way, it's not 1.3 oz. 1200 ml is equal to 40.567 oz. 200 ml is equal to 6.7 oz.

I suspect that the 1.3 is meant to be 1.3 times a quart (32oz.) which is 41.6 ounces. Clear as mud.

Last edited by bobl; 07-14-2018 at 10:35 AM. Reason: content
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post #24 of 85 (permalink) Old 07-14-2018, 12:06 PM
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Further thinking, 40 ounces is a quart and a fourth (32+8oz.). That sounds like too much. I would go with what John said. Damn book anyway.
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post #25 of 85 (permalink) Old 07-14-2018, 12:48 PM
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Yes, 1.3 US oz converts to 38 milliliters so the numbers in the book don't work and neither of the volumes is plausible.

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If you think reading is tricky, how the hell are you going to follow troubleshooting directions?
"Riding well is difficult, riding poorly is easy and painful."
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"We're all here because we're not all there" - Guy Favron on Gold Rush

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post #26 of 85 (permalink) Old 07-14-2018, 01:31 PM
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The 2001 manual update changes that from ounces to quarts..... so 1.3 qt in 30 seconds. That's about 14 ounces in 10 seconds. Compared to modern 750, which is a minimum of 6 ounces in 10 seconds. I'd say if you can get 10 ounces in 10 seconds, you're probably good.
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post #27 of 85 (permalink) Old 07-14-2018, 03:14 PM Thread Starter
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ty every one for your help. this issue has been alot to deal with i love rideing and this year i prob put close to 2000 miles on bike, its been tuff i was ready to give up, i could not get such good info anywhere else... beleive me i tried every bit of free time went to the bike the past 2 weeks weather up late reading forums and watching utube or wrenching .... thanks every one
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post #28 of 85 (permalink) Old 07-14-2018, 03:19 PM Thread Starter
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ev1 i know has called me crazy and said get a newer bike blah blah its not worth the money or effort, no offence to anyone call me nuts if u want i love my bike i think a 750 is the perfect ballanced bike and i think after 2005 bikes(gsxrs) changed the way they looked and im not a fan ...
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post #29 of 85 (permalink) Old 07-17-2018, 11:25 AM
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Quote:
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ev1 i know has called me crazy and said get a newer bike blah blah its not worth the money or effort, no offence to anyone call me nuts if u want i love my bike i think a 750 is the perfect ballanced bike and i think after 2005 bikes(gsxrs) changed the way they looked and im not a fan ...
I wholeheartedly agree with this whole statement. VERY well said... There is another possibility that hasn't been brought up. You could be getting a voltage drop in the upper RPM range. Lowering the voltage to the pump, as well as everything else. Won't hurt you any to throw a DVOM to the battery while running it up. Just the last thought I've got. I'm thinking the sensor test might get you where you need to be, but can't hurt to check it anyway...

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post #30 of 85 (permalink) Old 07-18-2018, 01:41 PM Thread Starter
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first time working on it in a while... fuel pump gave me 40 psi not 42 or 3 with a guage, i measured volume with a measure cup and timer, in 10 seconds i did get 10 oz, i did volume test 2 xs to be sure
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post #31 of 85 (permalink) Old 07-18-2018, 02:03 PM Thread Starter
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i unplugged all 3 sensors, ran it and nothing changed
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post #32 of 85 (permalink) Old 07-18-2018, 02:12 PM Thread Starter
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so playing with them 3 sensors plugging them in and takeing off while bike running, the only sensor that did not change the way the bike ran was iat , it has a green plug
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post #33 of 85 (permalink) Old 07-18-2018, 02:14 PM Thread Starter
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i also sprayed all over vac lines and under fuel inj while running and no where i seemed to spray did it make a diffrence the way it ran
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post #34 of 85 (permalink) Old 07-18-2018, 02:29 PM Thread Starter
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no voltage drop at the battery while reving at the battery
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post #35 of 85 (permalink) Old 07-18-2018, 02:29 PM Thread Starter
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ty spider and chuckster but i think im stuck again
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post #36 of 85 (permalink) Old 07-18-2018, 02:31 PM Thread Starter
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unless i get some feed back the only thing that seems not to respond is the iat, im not sure if that can cause this... but should i replace it?
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post #37 of 85 (permalink) Old 07-18-2018, 02:57 PM
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Unless it caused it run perfect, don't replace it. Sounds like fuel problem. Closing the STVA introduces an air restriction which matches the fuel restriction and it runs good. Time to do fuel pressure and flow tests.
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post #38 of 85 (permalink) Old 07-18-2018, 03:23 PM Thread Starter
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i did fuel preasure test, i got 40 psi i got 10fl oz in 10 secs, i did test 2xs
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post #39 of 85 (permalink) Old 07-18-2018, 03:26 PM Thread Starter
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nothin g makes it run right accept closeing them top butterflys... i am stuck i have not given up , i dont know wat to do next
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post #40 of 85 (permalink) Old 07-18-2018, 03:27 PM Thread Starter
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i can only hope the guages i rented from auto zone were off 2-3 psi but 40 psi on the nose 2 xs
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