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Discussion Starter #1
2002 GSXR600. compression, leak down, injection, computer, fuel pressure/pump, cam timing, no wear on cam, new boots for intake to head just replaced, all are fine. BUT, I only get vaccume from cylender 4, the one on the far right. You can litterally cap your hand over the other 3 while it is running and it doesn't slow the motor one bit! what is this all about???????????? the back of the intake valves are blackened. vaccume leak? I pulled all the hoses off & nothing not a change. This is sure one thats got me and the mechanics stumped. no knocking or any funny sounds. I got out an incense stick and moved it all over the intake and engine while it was running and couldn't find any vaccume leaks.
 

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cichlid said:
I only get vaccume from cylender 4, the one on the far right. You can litterally cap your hand over the other 3 while it is running and it doesn't slow the motor one bit! what is this all about???????????? the back of the intake valves are blackened. vaccume leak? I pulled all the hoses off & nothing not a change. This is sure one thats got me and the mechanics stumped. no knocking or any funny sounds. I got out an incense stick and moved it all over the intake and engine while it was running and couldn't find any vaccume leaks.
Let's start from the top - you are saying that all the components and tests you checked out are good, right?
When you say you only get vacuum on c4, do you mean that it is the only one which produces a vacuum in the vacuum lines? When you cup your hand over the other three, do you mean you're covering the intakes of the carbs/throttle bodies? Black valves are normal. You say the engine runs - does it run well or rough?

Incense won't necessarily find leaks, but WD40 will.

Answer these questions, and add any other info you can think of, such as how the problem first started, what has been done to the bike, etc. Be as thourough as you can, and hopefully we can figure out what's up........
 

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Discussion Starter #3 (Edited)
thanks for the help! it shows no change in idle when you put your hand over intake hole on intake manifold 1,2,3, or all three. it almost pulls your hand off if you put it over #4. It runs a bit rough, low performance at higher speeds, and no performance before 20mph. very had to get it up to 20mph you have to keep the throttle pulled just barely, keeping the rpms around 7ish and slowly let the clutch out, untill you get to 20mph. it doesnt make any funny noises. The idle flutters when you try to hold it around 2-3 grand, that is where you see it jump the most. It flutters in a specific pattern. Also when you are exelerating at higher rpms the enging sounds like it's going up in stages, higher, higher..... about every second or so. This may sound funny, but the guy that sold me the bike swears it ran fine up until the last tank of gas. He had put 5000mi on it since 6 months ago, so he has been riding it, that's for sure. I'm going to check the valve clearance tonight. I swear it's a vaccume leak, but where?
 

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wow, your situation is troubling to say the least. ya did alot of testing and i will assume it was done accurately. to have the symptoms you have only a few thoughts come to mind, unfourtunatly now, as i write this, no clear answers just thoughts. one, if theres no vacuum as you describe it at 3 of 4 intake tracts one would assume you have three cylinders not making any power and the likelyhood of the engine running in such a state is unlikely. so to doublecheck my train of thought.. if you have it running and kill one cylinder at a time by say pulling one spark plug wire at a time, theres no change till the 4th one is pulled? then it dies completly? a exhaust restiction in three of the cylinders would theorictically give you your symptoms, the operative word here theoritically. all the other things i can think of at this time you allready eliminated though your testing. as i ponder this more , if my brain doesnt fry, i will post back. i cant wait to see how this one pans out, good luck. how did you check the cam timing? you had the valve cover off to visually inspect the cams? didnt that era gsxr have a history of tensioner problems?or not...
 

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You say you did a compression check on the bike, and it was good? If so, that should eliminate any problems with your
head gasket, rings, and valves, but your description sounds to me like one of those. If the camshafts were mistimed that badly, your engine would have destroyed itself by now.

B1 may be onto something with the exhaust - Does your bike have an exhaust valve? You've examined the headers, and none of them are flattened?

Post back with pics, if you can, and anything else you can think of that describes what's happening. If you do find the problem, let us know, so we'll all know next time. Good Luck
 

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Discussion Starter #6
THE PLOT THICKENS! ok, just checked the valve clearance. the exhaust clearance is fine. .010 between .008-.012 is to speck. but the intake clearances are all the same .006 a bit tight. .008-.012 speck. Also I put a vaccume tester on the intake ports. each intake was pulling the same amount of air/ unlike the mechanics deduction! It is just the fact that when you put your hand over the last intake that the bike stalls. what an idiot! I'm going to pull one ignition at a time and see how it affects the running.
 

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Discussion Starter #7
GET THIS! I pulled ignition wire from cylinder 2 & 3 and it runs just the same as it did with them plugged in! electrical? Ya think?
 

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Discussion Starter #8
Ok, now i'm thinking electrical. 1st thing that comes to mind........ throttle positioning sensor. I unplugged it, the rpms went up, I adjusted the throttle back down, and..... IT HAS HP. IN LOW RPMS! IT HAD SQUAT BEFORE! My valve cover leaks now & the red light is on, but i'm pretty close to figuring this out. If a throttle pos sensor is faulty, and you unplug it, will the engine run as good as it would with a working one? What I mean is, doesnt it make sense that this is the problem? and if I replace it the engine would run even better?
 

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dontget side tracked, you verified that cylinders 2 and 3 are not making power, find out why. verify they both have spark, i beleive there on the same coil. post back.
 

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Discussion Starter #10
They get spark, just not as much "visually" as the other two. should i put them on a volt meter of some kind? I'll go buy one if I need to.
 

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Discussion Starter #11
OH YEA BABY!!!!!!! I pulled the injectors/bar off and cleaned it out. Cleaned out every injector with a compessor hose/choke cleaner. the stuff that came out was black with flecks of rust. i remembered when I pulled the filter/pump out the pre-filter was full of rust. It runs like a champ! WOW! looks like now I'll need to replace my filter if all that crap is getting through.
 

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I had read this last week and after your post of all the stuff you'd tried I had nothing but was interested in the outcome.

Now I have some suggestions. If your prefilter's that bad, its coming from your tank, probably. Take the winter to pull the tank and evaluate its condition. If its rusty, time to coat it with something (I recommend POR-15). Drain out all ga, vent off until the fumes are effectively gone, put in KNOWN number of nuts and cap. Shake like crazy and flush out with water to get as much rust out as possible. Apply pretreat and coater as directed. Don't skimp on any directions.

Then keep an eye on that fuel filter for the next six months.

BTW, keep you tank full during the winter, non-riding months with fuel stabilizer. Keeps the tank rusting minimal.
 

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Discussion Starter #15
no joke, with used bikes sometimes you really don't know what you're getting into. We learn as we go.
 
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