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Discussion Starter #1
So, I've searched these forums repeatedly and have found many who've experienced my issue but none of their solutions worked for me. In brief, I picked up a K8, Gixxer 600 last year with 700 miles on it that had been stored for years with a couple gallons of gas in the tank and no fuel stabilizer. The thing had been parked in a garage all that time (it looks showroom new) and only started by the owner a couple of times a year. When I first bought it, it ran great all around, starting, low speed and would pull easily to 12k RPM, but then power would drop off. I wasn't too worried about it but it progressively got worse over the last year while I was putting 4,000 miles on her. It began to bog at 8,000 RPM at WOT, but a slight backing off of the throttle and it would surge forward as if it had just gotten fuel back. Recently, it got worse and started cutting out at 6,000 RPM with the same surge of power with a slight backing off of the throttle. Here's what I've done so far,

1. SeaFoam and Techron fuel cleaners run through the tank
1. Bypassed the kickstand switch
2. O2 sensor eliminator installed
3. Exhaust Valve disabled and open
4. TPS adjustment (several times)
5. New Fuel Filter and Fuel Pump
6. Injector coupler resistance measurement
7. Verified no kinked lines
7. Installed a set of used throttle bodies that came with all injectors, TPS, STVA and off of a running donor, same year and model

Note that when I replaced the fuel pump, I found the plastic filter/screen was dissolved and there was nothing left but the frame that holds the screen. The inside of the tank has a brownish film coating the inside where it looks like the fuel level was when the filter/screen dissolved and stained it. It does not come off with a solvent so I don't think it's an issue, just indicative of what happened with that ethanol gas sitting in the tank all that time.

So today I'm thinking I'll solve the issue with the new throttle bodies and parts that came with them but no, it's actually starting to bog down at about 5,500 RPM now instead of 6,000 and doesn't feel as strong down low as with the old throttle body set. It starts and idles fine, it runs below 5,000 RPM like a new bike, but twist the throttle to wide open and she'll bog down without accelerating until you back off the gas just a tad.

So, short of spending $750 to $1,000 at a dealer to solve a problem on an 8-year-old bike that is practically new, does anyone have an idea of what I could check next? Is it possible the ECU has an issue from sitting so long? What would be the next thing to check on my own at home? And, if I take it to the dealer, something I don't want to do, what should I tell them and have them check?

I'm an old-school drag racer and have done a ton of work on bikes before they were loaded up with ECU's and all these sensors. I'm finding this troubleshooting experience to be a pain in the butt to diagnose and solve. Maybe I should look for an earlier era supersport to wrench on unless you guys can give me a clue as to what I'm unable to find and solve myself. I hate handing $ to a dealer who wants to charge me $125 for an hour on a dyno, which I know will only verify the issue I already know I have.

The sad part is, the bike starts fine, idles fine and rides perfectly at lower RPM, it's just when under load at WOT is where it bogs down and won't pull redline without sounding like it's hitting a rev-limiter or running on two cylinders or starving for fuel.

Any help and all suggestions are appreciated. I'm ready to burn this bike to the ground I'm so frustrated. Thanks in advance.
 

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As was mentioned in most if not all other "won't rev past" threads, you've got a clogged high pressure fuel filter in there which you've probably overlooked; do a fuel flow test to make sure.
 

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Discussion Starter #3
As was mentioned in most if not all other "won't rev past" threads, you've got a clogged high pressure fuel filter in there which you've probably overlooked; do a fuel flow test to make sure.
You're right, I don't recall reading about a high-pressure fuel filter, but see it right there in the service manual. I didn't notice it in the housing when I changed the pump and its filter. She's my only transportation so I'll have to wait until my next day off to pull the pump out and check. Thanks for the heads up and here's to hoping it's that simple!
 

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I know things... A lot of things.
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She's my only transportation so I'll have to wait until my next day off to pull the pump out and check. Thanks for the heads up and here's to hoping it's that simple!
Do a fuel flow test before starting to take things apart. If you fail the volume test, you can then consider redoing the test with just the pump, without the filter, to see if that's in spec. If so, it's probably the filter. You mention changing the pump as a previous step. If the replacement pump was a cheap ebay part, I'd suggest testing the OEM pump and using that, if it tests ok.
 

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When I had this problem I ended up replacing the fuel assembly but the problem was actually worn fuel hose clamps. They were basically not sealing the fuel flow and pressure. If you have spring clamps like my bike did I fixed the issue by installing the clamps that screw in so they don't wear out over time.

I was also experiencing a lot of fuel guzzling/overflow when I would top off.

Just trying to throw out a possibility.
 

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Discussion Starter #6
As was mentioned in most if not all other "won't rev past" threads, you've got a clogged high-pressure fuel filter in there which you've probably overlooked; do a fuel flow test to make sure.
Ah, if things were so simple. I pulled the fuel pump again and looked for the secondary high-pressure fuel filter, and there isn't one. I looked in the K8 service manual and it shows it, but there isn't one in my bike and no place for one. I called the local Suzuki dealer's parts department and they assured me I don't have one. They suggested I check and/or replace the fuel pressure regulator but rather than continue to throw parts at it, I decided to buy a complete pump and assembly off of a low miles donor (4,000 miles), also an '08. I verified this one does not have the mystery secondary high-pressure fuel filter so am still confused as to why the K8 manual shows one. I threw the used assembly in today and low and behold, it solved this PITA problem! Finally!!

I wish I knew what the actual issue was, certainly related to the pump. As someone mentioned above, a cheap eBay pump is what I replaced the original one with so that could have been the issue. I'd like to know more about the dealership saying it could have been the fuel pressure regulator since I didn't swap it from the used unit to the original one first to see if that was it (it was much easier to just install the whole assembly and test). Could that have been the issue or was it likely the cheap replacement pump? I never got around to flow-testing either pump so may never know the answer, but hey, at least it's fixed and my almost new (700 miles on it when I got it last year) is now running like a champ. I've put 4,000 miles on it while dealing with this issue since she's my only transportation (unless I borrow one of my daughters bikes) so I'm glad to have this issue behind me!
 

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Really glad you fixed it, kudos to who gave the idea.

You explained it well and methodically.

I kinda like to hear about your daughters bikes?

FWIW, I was riding today and met up with 2 women on bikes.

We rode for quite awhile outside of SW milwaukee, till we all had to go.
One was a very nice Harley, and one was a very nice Indian.
Both had bags, small ape bars, no fairings, and looked really cool.
Cool woman too
 

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Discussion Starter #8
Really glad you fixed it, kudos to who gave the idea.

You explained it well and methodically.

I kinda like to hear about your daughters bikes?

FWIW, I was riding today and met up with 2 women on bikes.

We rode for quite awhile outside of SW milwaukee, till we all had to go.
One was a very nice Harley, and one was a very nice Indian.
Both had bags, small ape bars, no fairings, and looked really cool.
Cool woman too
Our oldest daughter has an '07 R6 and a play '02 YZF600 she's trying to learn some stunts on. Youngest daughter has an '04 250 Ninja, which is the one I borrowed most of the time while the Gixxer has been worked on during my one day in a row off each week, lol. We're a riding family, even my wife rides though she's between bikes right now. I've been riding 37 years, all on sportbikes, and have owned 19 bikes so far. I actually titled the 2nd 1986 GSXR 1100 registered in Florida! Paid cash for it in December, took delivery in March of '86. I've personally run 9.26 in the quarter mile and still love speed even though I've become more cautious with age, lol. They (wife and daughters) are still in the minority but take pride in that... My oldest, my son, is also into bikes but hasn't spent much time riding in recent years due to his working 7 days a week running his realty company here in Florida. I picked up the Gixxer last year since I was between rides and couldn't resist an '08 with only 700 miles on it and it had only the first service and oil change done to it when it got parked. I'm itching for a liter bike again since I enjoy the extra power and comfort when highway riding and the occasional quick street race. But I have to say, now that I've got the 600 running right, I'm going to enjoy her until mid-year 2017 when I'll be ready to upgrade!
 

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It's almost 100% certain you could have figured the issue out by simply doing a fuel pressure and fuel flow test, both are in the Service manual. As you found out, the hard way, the "Throw all the parts at it to try to fix it" game is a costly one that does nothing to guarantee that it will fix the issue. This is why proper testing is what you need to do to find the issues.
Note: rather than an "I told you so," this is more of advice to future posters that search for this exact issue and for you to not repeat the same mistake.
 

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I know things... A lot of things.
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Ah, if things were so simple. I pulled the fuel pump again and looked for the secondary high-pressure fuel filter, and there isn't one. I looked in the K8 service manual and it shows it, but there isn't one in my bike and no place for one. I called the local Suzuki dealer's parts department and they assured me I don't have one. They suggested I check and/or replace the fuel pressure regulator but rather than continue to throw parts at it, I decided to buy a complete pump and assembly off of a low miles donor (4,000 miles), also an '08. I verified this one does not have the mystery secondary high-pressure fuel filter so am still confused as to why the K8 manual shows one. I threw the used assembly in today and low and behold, it solved this PITA problem! Finally!!

I wish I knew what the actual issue was, certainly related to the pump. As someone mentioned above, a cheap eBay pump is what I replaced the original one with so that could have been the issue. I'd like to know more about the dealership saying it could have been the fuel pressure regulator since I didn't swap it from the used unit to the original one first to see if that was it (it was much easier to just install the whole assembly and test). Could that have been the issue or was it likely the cheap replacement pump? I never got around to flow-testing either pump so may never know the answer, but hey, at least it's fixed and my almost new (700 miles on it when I got it last year) is now running like a champ. I've put 4,000 miles on it while dealing with this issue since she's my only transportation (unless I borrow one of my daughters bikes) so I'm glad to have this issue behind me!
What part are you missing exactly? I'm not familiar with the K8 pump, but as far as I can see, the only part that could contain the filter would be the one marked as "REGULATOR", with part number 15610-27G00. I suppose that's the part both you and your dealership suspects of causing the problem and I assume you have it in both the old and the new assemblies.

Regarding discovering the source of the problem and as Just_Nick suggests, a set of flow and pressure test should have been enlightening. A failed flow test would indicate that some part of the system is clogged, while a failed pressure test, would indicate and internal leak of some kind (since you didn't see any fuel leaking). Performing the tests, once with the complete assembly and once with just the pump should help to decide whether the problem was caused by the filter/regulator, or the pump itself.
 
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