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Discussion Starter · #1 ·
Alright, figure ill post now to see what you all think. I've researched a lot already and not sure where to go from here..

As the title says, I have an issue with the bike bogging down at wot. Doesn't matter what gear, speed, rpm.. its only when twisting the throttle all the way. I can go about 90% without issue, will get to speed and redline etc.

Bought the bike about 5 weeks or so ago and have put about 1500 miles on it so far. All stock when I got it and I haven't added anything to it, yet.

At first I didn't notice the issue as I was going pretty easy on it with it being my first bike and all. After a few times out and getting more comfortable I noticed the bogging issue at about 50-60% throttle. Did a little research and started with the tps sensor. Found that it was out of spec (_C00) and adjusted it to where it should be (-C00). I know thats more for "herky jerky" but surprisingly it seemingly fixed the bogging issue... until I went wot. So I threw some plugs at it (it was due for some per the haynes manual anyways) and a new air filter. Went ahead and threw on a new tps sensor as well, just in case that might fix it but it didn't.

After more research I started to think the problem is fuel related. Last night I pulled the pump and went through it. Wasn't as bad as some pics I've seen but the strainer was dirty. I cleaned it up and reassembled but didn't mess with back flushing the filter. Ran it afterwards and still have my issue.

I planned on pulling the pump again and back flushing the filter today but ran a flow test first. I got over 200 ml in 10 sec. I followed a video and did the following: with kill switch off turn key on, flip kill switch to run, fuel flows, kill switch off then back on again, fuel flows again, test complete. I assume that's a fair way of checking it.

So now my questions are:
If I'm getting good flow do I need to pull the pump again and back flush the filter?
Do you think there is something else causing my problem?
If its likely something else causing this, should I go ahead and back flush the filter anyways?

Side note: realized I'm missing the tank vent hose and plan to replace. From what i read it seems it also runs down the left side of the bike to the bottom like the overflow, but confirmation would be nice! I blew both of them out last night.. the vent tube seemed pretty clear but the overflow was blocked up. All clear now.

Any and all help would be greatly appreciated!

296091
 

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Welcome and good diagnosing so far.

The most common reason for bogging at higher power is a fuel supply issue as you mentioned.

The pump "primes" for 3-5 seconds each time the ignition/kill switch is turned on so your 200 ml sounds valid. It is a little low compared to what I've measured but meets the 168ml minimum.

The other important part is the pressure. A pump can be putting out volume with no pressure, just as you are testing, but be short of flow under pressure. Check the discharge pressure next, it should be about 43psi. Pressure is important as the bike does not measure fuel flow but just regulates injector open time. Low pressure = low injector amount = lean condition.
 

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The ultimate fuel supply test is to connect a pressure gauge so that you can read the pressure while riding under high demand (RPM & throttle) conditions. But it's a hassle to set it up. If the supply is good, the next thing to check is the injectors. There's a fine screen on their inlets and you can sometimes see crap collected on it. My K6 1000 has a .4" OD water drain hose and a 5/16" OD vent hose. The vent hose has a lengthwise slit about 12" from the tank. I bought another when I first noticed that only to find that Suzuki makes them that way.
 

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Discussion Starter · #4 ·
Appreciate the responses gents. I knew about the pressure test, just haven't completed it yet... need to get a gauge. Idk that ill be able to hook it up and ride, at least not the first time around, but will check it with the bike on the stands. Will see what the pressure test shows then I guess look into the injectors.

Ill have to get a hose for the vent soon and will run it alongside the overflow line then. Read about the slit, not sure what the point is but I guess they wouldn't put it there for no reason.

Will report back!
 

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The service manual spec is for just the pressure with no flow. Unless you are running some super tuned and turbo'd bike, the static pressure check should be fine.

Auto parts stores used to "rent" tools like a fuel pressure gauge. If not, the Harbor fuel pressure test kit is less than $20 or the vacuum/pressure gauge is $14.
 

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Discussion Starter · #6 ·
The service manual spec is for just the pressure with no flow. Unless you are running some super tuned and turbo'd bike, the static pressure check should be fine.

Auto parts stores used to "rent" tools like a fuel pressure gauge. If not, the Harbor fuel pressure test kit is less than $20 or the vacuum/pressure gauge is $14.
Yeah, I'm about to check into renting one. If not, will buy and add to my collection of tools. Might need it again one day.
 

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Discussion Starter · #7 · (Edited)
Alright, got a gauge on loan.. Here are the results..

Initial prime only gave me 30 psi but when I started the bike it jumped up to 43.

Flicked the kill switch back off, released the pressure, then flipped the kill switch back on. This time I got 43 psi on prime. However, once the pump stopped priming it dropped down to about 38, then about 35, then I released pressure.

Repeated the process again and got the same results as the second time around... 43 on prime and drops after pump kicks off. Start the bike and it jumped back up to 43.

Now, with the bike off, I have not released the pressure yet from the last time and as I sit here typing this the pressure has slowly been dropping.. currently at about 28. Idk if this matters, but figured I'd mention it.

So, what do yall think?
 

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Hmmm.... the pressure sounds fine. The pressure bleeding down is normal.

If it was my bike, I'd back flush the high pressure filter first, double check the flow and pressure after assembly and see if it is fixed. If not then you need another idea. Possibly what Billy said of the small filters in the injectors themselves.
 

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As best I can tell, Suzuki has a philosophy of trying to reduce the load on the electrical system while cranking. An example is the Start switch cutting power to the headlights. They also do it with the fuel system via the "prime". There's a check valve in the fuel pump motor to prevent backflow. The prime pressurizes everything and the pump then shuts off until the engine is running. Because of the small volume of the system, i.e. it's the fuel filter and the fuel lines, plus you're pressurizing with a liquid instead of a gas, I'm not surprised that the pressure drops a bit at first and later continues to drop. But I don't think that it means anything. Your pressure sounds fine, though it doesn't rule out a clogged main filter. Your flow test wasn't done in the standard Suzuki way but the results still sound good. Backflushing the filter won't hurt. There are videos about cleaning the injectors with carb cleaner.
 

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Discussion Starter · #10 ·
Alright, ill back flush the filter this evening and then test pressure, flow, and hopefully ride it (weather permitting) to see if my problem still exists.

What is the suzuki way to test flow? The haynes manual only mentions the pressure test. I've read so many threads online I can't remember if I saw someone explain it or not. Is it just hard wiring the pump to a/the battery to let it run continuously for x amount of time?

Will look into cleaning the injectors next! I did run some lucas fuel injector cleaner through it a few weeks ago... but I know a lot of people claim that those do not really work.
 

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Nothing too special with the Suzuki method. It just says to jump power directly to the pump, run for 10 seconds and measure the amount.
 
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Discussion Starter · #12 ·
Alright, just went through with back flushing the filter... gas coming out was clear from the start. Ran roughly two gallons through it.

So.. flushed filter, flow is good, pressure is good. Guess its on to injectors...
 

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Alright, just went through with back flushing the filter... gas coming out was clear from the start. Ran roughly two gallons through it.

So.. flushed filter, flow is good, pressure is good. Guess its on to injectors...
And rode the bike and it's still bogging?

Do you still have the stock exhaust on it? Do a quick check that the exhaust flapper valve is opening or open.
 

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Discussion Starter · #16 ·
And rode the bike and it's still bogging?

Do you still have the stock exhaust on it? Do a quick check that the exhaust flapper valve is opening or open.
I have not ridden it again. Left the tank off and took off the air box so I could look at throttle bodies and injectors easier. Was waiting on a mechanic friend of mine to come by and look into it with me but looks like its not going to happen tonight.

After back flushing with a couple of gallons and nothing but clean gas coming out, along with the pressure and flow test yesterday, I'm thinking the pump assembly is not my issue.

Stock exhaust is on but the valve is always open and cables are missing, which I assume was done by a prev owner.

Still trying to think of what other issues there could be. No codes show in dealer mode. Runs great until wot.. but once you twist that throttle all the way it bogs hard, spitting and sputtering, and rpms and speed remain the same for as long as you are hold it. (n)
 

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Runs great until wot.. but once you twist that throttle all the way it bogs hard, spitting and sputtering, and rpms and speed remain the same for as long as you are hold it. (n)
What you describe sounds like the bike is leaning out on WOT, the question is why.

Is there a Power Commander or similar on the bike?
 

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Discussion Starter · #18 ·
No power commander currently connected, but one may have been at some point as there is no plastic around the wires for the tps sensor but there is some electrical tape around the middle where it could have been spliced (from what I've seen you splice one of the wires of the tps when installing the pc?). Also not sure what this yellow plug is shown on the pic.

Couldn't bogging also be caused by running rich?

296096
 

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Discussion Starter · #19 ·
Before pulling injectors, throttle body, etc I think I'm going to rent the fuel pressure gauge again and rig it up to go ride with it as billv mentioned in his first response. Found a post earlier today of someone having similar issues with their SV1K and it ended up being the fuel pump.. static pressure and running pressure were fine until wot, then the pressure dropped to almost half..


If pressure tests fine at wot then I guess I can rule out the pump completely and move on to injectors and whatever else from there. Itll prob be another day or two before I can get around to it though. :rolleyes:
 

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That test can't hurt. Please post up the results. I'm still scratching my head on this one.
 
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