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  1. #1

    951 GSX runs weird - seems like ignition but?

    1998 GSX limited (97 production)

    After purchasing this used item, I knew I was going to be giving it some serious work as it barely ran when I bought it, so here is what I have done.

    By-passed resonator

    Updated cooling lines to feed from pump into engine rather than exhaust (teed lines to water regulator and re-routed accordingly)

    Replaced fuel lines.

    Tore down carbs and cleaned (mag side carb filter was literally plugged with solid rubber)

    Replaced steering cable

    Serviced pump

    Trimmed ends of spark plug wires

    Drained all fuel replaced filter

    Pulled head and got a look at cylinders/pistons (which looked perfect not but a single minor line on one cylinder)
    Compression perfectly equal at 130, my gauge may read low, but it seemed like new ones used to read 135 on that gauge when I was in the business

    Here is what I have going on. After getting it started in water, engine will idle fine, even run fair at quarter to third throttle, but try to even slowly come into it at first and it will behave as if it is starving on the low end, then eventually clean up and make it to speed, running fine for the most part.

    As I continue to work my way up in RPMs, it gets better and eventually runs at WOT. I can ride it at WOT for as long as I want, however the engine wavers on the top between 5500 and 6200 RPMs. It will run OK at 5500, but you can feel that it is trying to hit that top speed which it intermittently does. I have ridden it 30 minutes at WOT several different times and no matter what, whenever I back it off down to idle or low RPM's or shut it off, I have to work my way back up to getting to the top, then it runs well except for that wavering on the top.

    I ran it on the top for as long as I could to make sure I got a decent look at the plugs and they looked good, maybe a little "wet" but really are shiny and dark, so it doesn't look lean at all. Before trimming the ends of the cables, it was worse, now it just takes less time to run "fair".

    No matter how long I ride it, if I shut it off, it stumbles it way back.

    Every once in a while, it just cuts off totally and if I back off throttle I can catch it and keep it running.

    If I run it at ALMOST WOT it will just run fine for the most part.

    Two little other items, the speedo will once in a while read zero and them come back, whether it is on digital or the needle. That sounds like a pickup problem and the fuel gauge doesn't display anything, not low fuel, nothing.

    Could this be a stator problem causing a short? Coil? It just seems odd that it would be consistently at those RPMs or speeds. It acts line a funky short on the top, like spark delivery is being interrupted. I was thinking that maybe once the temps in the cylinder get high enough, that maybe it is easier to fire.

    It's not fuel delivery unless the carbs are acting funny, but the plugs always seem to be a little "wet".

    Low speed screw is at 1 1/2, high speed is closed. I tried changing low speeds to even 2 1/2 and it just idled rougher and smoked like crazy. Tried opening high speed 1/4 turn and no change. I suppose I should check all the grounds and replace the plug wires in full, but that has never fixed anything for me. Then again, I used to buy a new one every year and this one is older.

    I know that there was some sort of stator problem in which pieces would mess with it and create a short on a wire. I am just wondering if anyone has heard of this behavior before and what the causes might have been.

    Oh yeah, cleaned RAVE valves too.


  2. #2
    what are your jetting and pop-off specs

  3. #3
    If i knew,...I wouldn't ask sea-one's Avatar
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    Aug 2009
    Quote Originally Posted by KYHI View Post
    what are your jetting and pop-off specs
    +1 thats what i was going to ask him. Also check your plugs for color reading and make sure the gaps are set right. Also are you having to use Ethanol fuels? and have you tried to variably pull on the choke any to see if it helps? Check the outer Crank seals, you can only check the rear one by running the motor and spraying some carb cleaner between the cases and pto and listen for any noticable rpm change. This is what would do.........let us know, goodluck

  4. #4
    I am assuming the carb components are stock, the engine has absolutely no mods, stock airbox and exhaust (except for by-pass) I will be removing them again this weekend and I will get the jet sizing and pump test them.

    The choke has been removed in favor of a primer setup, no real changes there other than maybe the sense that pumping the primer is putting too much fuel into system. When first purchased, the only way I could get it to run even half-way decent was to squirt fuel in with the primer. I should add that when I first bought it, the accelerator pump was set to not even to pump anything. I realize now that may have been intentional for some reason, but I set it to the factory settings.

    No vacuum leaks, case checks out (surprisingly)

  5. #5
    I run 82.2 pilot jets - 165 main jets and 2.0N/S with 95 gram spring resulting in 19-23 psi pop-off and using the stock air box

    The carb vent hose is no longer attached to the solenoid, but rather open vented

    Also when setting pop-off pressure (the stock 97.5 gsxl has a 3mm shim installed under the pop-off spring - sitting in the bottom of springs bore) - it needs to be removed...

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