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  1. #1

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    Ultra150 running rich on #2 cyl.SERIOUSLY DOING MY HEAD IN!

    Guys,i'm just about stumped on this ski of mine.I've recently bought it and it only has 48 hours on it.It idles fine but between 1/4 throttle and just over half throttle,or bout 5,000rpm,it runs rough/splutters.Over 5,000rpm or past 3/4 throttle is great and smooth.Several plug readings show middle cyl plug always black/oily.The other 2 nice brown color.Engine was fully rebuilt,new crank and pistons but was done a few years ago and left till i got it.Compression is an even 120psi in all 3.

    I've had the carbs off at least 10 times.I've replaced the slide diaphrams and guides,tried going down on the low speed jet,raising the popoff,nothing has made any difference with the carbs.I've even tried a brand new set of CDK2 carbs i adapted.It starts and idles better but #2 plug is still black.I've also swapped the coil plugs and leads around,but still no difference.Nobody else seems to have had this problem.Carb issues seem to a lean condition,not rich and i've never heard anyone complain an ignition issue like mine,so i am stuffed if i know what is wrong with this thing.

    #2 cylinder seems to run a bit cooler than the others.I'm thinking of pulling the oil line off that carb as i'm also running premix till i break it in fully.Is there anything in the engine assembly procedure that could cause this to happen? Jetsport are known for their crap WSM parts.Thanks for any help.


  2. #2
    steve45's Avatar
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    I'm assuming that the engine is still set up as it was originally, with the oil injection system. A few people, mostly racers, remove the injection system, but this requires modification of the crankcase. The oil pump actually has 5 outputs. Two outputs pump oil to the balance shaft bearings, and from there, the oil goes into the front and rear cylinder crankcases. The center cylinder gets more oil to the carburetor because the oil flow isn't split as it is on the front and rear cylinders. Doing this mod requires changing the balance shaft oil every 25 hours or so, a royal pain for the average rider.

    I don't know if the above is related to your problem, but perhaps the front and rear cylinders are not getting enough oil. You're still running pre-mix in addition to the injection, to those plugs should be oily, too.

    Check the calibration marks on the oil pump, and also inspect the oil pump cable for fraying. It's a common problem.

  3. #3

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    Thanks Steve i checked the oil pump marks when i replaced the oil lines.Also there is always some oil under the engine.I've looked underneath with a mirror and run my hand along the cases but there's no obvious leak.As far as i can tell,the outer cylinders are correct due to the nice brown plug color.I'm trying to apply logic here,either #2 can't burn the applied mixture until certain load,there is too much mixture,or too much oil,which could explain it running well in the upper range.

    I might try temporarily disconnecting just the carb oil lines and see if the color gets darker on 1 and 3,and gets lighter on 2.There is only 1.3cc per 2min at oilpump full throttle going to 1 and 3 due to balancer lubing according to the manual.There is a slight whine(not pump)so i am worried the balancer gears aren't getting any oil.The motor has only been run for about an hour in water all up so far so hopefully i can fix any issues without blowing it up.

  4. #4
    steve45's Avatar
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    The balance shaft bearings should be pre-lubed during assembly. Perhaps they weren't.

    Like I said, I think they should all be a little oily.

  5. #5

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    Ok,is there a way of checking the rear balancer bearing oil? I see there is a bearing cover bolted on the back of the case,can it be used to inspect the bearing condition and oil volume?

  6. #6
    steve45's Avatar
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    I don't know if you can check it without disassembly. Do you have a manual?

  7. #7
    chk all reed valves [ pull them out ] and carb jets, someone could have tampered with the jets [ drilled them out ]

  8. #8

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    I've run the ski without any oil lines going to the carbs with premix in the tank.The ski runs much better.Plug chop reveals #2 still black/sooty and the others are light brown.The heat off the cylinders feel more even too.Mike,i've removed all the reeds and all are very good and i've tried going to a smaller low speed jet and heavier popoff spring.I think my oil pump is faulty and possibly the case check valves as well as i expected the outer plugs to be a bit darker having premix and oil injection simultaneously.I could jet the centre carb down to accommodate,but shouldn't really when i know there is an issue elsewhere.

  9. #9
    Self Confessed Day Dreamer toomanytoys's Avatar
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    Quote Originally Posted by 123456 View Post
    chk all reed valves [ pull them out ] and carb jets, someone could have tampered with the jets [ drilled them out ]
    Yep, check the reeds on #2

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