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  1. #1

    Can't get STXR right, plug chop pics included

    TL;DR Plug chop pics at bottom I'm at a lost to what is really the issue, but I suspect the carburetors.

    I recently got a 2003 Kawasaki 1200 STX-R that had been sitting. I think its getting close, but I'm still not there. Here is what I have done:

    I've been through the carbs and replaced the fuel pump and filter. On the carbs I swapped over the diaphragms and some other parts from my 1100 CV carb racks I had lying around. I've double checked anything I used from it to make sure it was OK. Everything seems to look ok, be clean and the slides move. Before I changed the fuel pump, it was struggling to keep enough fuel in the filter. My oil lines check out now after I replaced a bad one, they all seem to flow but may have some air in them. I figured better safe than sorry, so I've got premix in the tank right now.

    Other things I've noticed: I think the ski is generally running hotter than I expect. My buddy's ultra doesn't seem to get as hot as this thing does just idling in the lake. I cleaned any blockages from all the pisser lines. I also pulled the heads to check things out. The pistons have .5 on top so I assumed it is sleeved and .5 over. Compression is about 118 even across all three. The cylinders do have some discoloration on them, almost like score marks the length of the stroke just outside the ports but it is smooth, I can still see crosshatching. I assume that is from PO or when I first started it before going through the carbs.

    I put a fresh set of plugs in, warmed it up and did a WOT plug chop. Here is a pic of what I got. The album has more:

    Click image for larger version. 

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    That is Cyl1/MAG, up top and 3/PTO on bottom.

    Best I can tell 1 in OK and 2/3 are lean and hot. Any suggestions? At this point I plan on going back through the Carb's again and double checking everything on #2 and #3. If I was just to buy OEM parts to throw at the rebuild, what should I do? Diaphragms, high speed needles and needle/seat/springs? Parts are pricey so I'd rather use what I have around from the 1100 CV sets I have and buy as little as I have to.

    Thanks in advance,

  2. #2
    Are you running the stock air box? Are the flanges on the top of the carbs the right way around to allow air in for the sliders. Are the rubber grommets on the air box the right way around to line up with the slider ports.
    Gaskets good under the carbs?
    Reeds in good shape? Gaskets good on the reeds

    It's been rebuilt so are the pistons in the right way. Arrow points to exhaust.

    Is the expansion chamber to water box hose ok, if a cooling system block occurs, that hose can burn up.

    Your compression seems a bit low, should be around 140 to 150. Did you check it with all 3plugs out and throttle at wot? If it has .5 in it and its not sleeved, that would be an issue, you can't hone the cylinders, they have to either be sleeved or re- naskil'd
    Is your gas tank check valve working?
    Get a triple pisser kit so you know the cylinders are cooling.

    Some places to start. Some cylinder pics would be nice, top of pistons tell a lot.

  3. #3
    Factory airbox, with new carb base gaskets and the ducts in the airbox and carb flanges in the right directions. I double checked in the service manual. haven't pulled the reeds and checked them yet. I checked the vent, I could blow in through it.

    The pistons looked intact, They didn't have the wash I'm used to, these were all black. but I haven't run it much and the plugs make me think its lean, if I pull the heads or bring the inspection camera I can check the arrow and get a pic this weekend.

  4. #4
    steve45's Avatar
    Join Date
    Feb 2008
    Sure looks lean to me. I wouldn't scrimp on carb parts, get new diaphragms.

  5. #5
    118 compression is about right in a stock engine. Mine always tested around 120.. you think its running hot? Is the pipe hot or sizzling? I agree with steve your issue lies in the carbs. If your running premix ontop of the oil injection your plugs should be nice and brown

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