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  1. #1

    93 sl750 not running

    Just got my engine inspected and rebuilt professionally. Got everything hooked back up and it wont run. The middle cylinder wont produce power. Its getting fuel and spark but not hitting. The ski wont go over 1/4 throttle in the water and the middle cylinder is also much cooler than the front and back. I've pulled all three of the carbs apart and they were spotless, the diaphragms look good. What else can I check or what could i have missed? Wouldnt have gone through rebuilding the motor but my family had $800 in rebuilding the hull after hitting a rock and it seemed stupid just to let it sit.


  2. #2
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    Quote Originally Posted by polproject View Post
    Just got my engine inspected and rebuilt professionally. Got everything hooked back up and it wont run. The middle cylinder wont produce power. Its getting fuel and spark but not hitting. The ski wont go over 1/4 throttle in the water and the middle cylinder is also much cooler than the front and back. I've pulled all three of the carbs apart and they were spotless, the diaphragms look good. What else can I check or what could i have missed? Wouldnt have gone through rebuilding the motor but my family had $800 in rebuilding the hull after hitting a rock and it seemed stupid just to let it sit.
    Welcome to the Hulk first!

    Who inspected what when? Then, who rebuilt it? I don't think there are any Polaris mechanics working on skis these days..

    Are the pistons facing the right direction? arrow pointing towards exhaust?

    Have you updated the fuel system? That would include, gas filters,oil filter,all gas lines including the tank,checking for cracks on the gas cap on the tank where the sender goes in. and the fuel lines in the tank if so equipped. And rerouting the fuel lines on the carbs too.

    These older skis have issues with the single outlet fuel pump, it gets weak and you usually burn a hold thru 1 of the pistons and loose power and compression.

    whats the compression on the cylinders?

    Its possible the stators' timing mark is not lined up with the crease on the cases. Flywheel could of sheared the woodruff key and its off a lil now timing wise.

    Are your grounds in the ebox tight?

    Is the lanyard in the start switch?

    Is the battery strong? it won't run right with a bad or dying battery.

    Is your ground wire to the engine cradle on and clean and tight? Loose grounds cause weird things to happen.

    So it does idle? Just when you hit it, it falls on its face? That could be the low speed aduster adjustment.

    Who set the carb settings on the carbs? what settings did he/she use? stock?

    Whats the compression on the middle cylinder?

    They should be warm to the touch,, anywhere from 103 to 152.. The thermostat lets the engine get to 143 degrees normally..

    Is the air box and snorkel on it still?

    Does it run better when the seat is off?

    Could be a weak coil too if your getting spark still and gas..

    What color is the spark off the plug when you ground it? if its yellow, its weak. a bright bluish white is what you want to see. something that will jolt ya. Yep, I got spark!

    Does it backfire?,,

    Did you put the diaphrams up to a bright light and look for pinholes? if you get back into the carbs, take out the main and pilot jets and get the numbers off them and write those down, comes in handy.. then you'll know exactly what your running,

    NGK 8 BRES plugs? .028" gap?

    Does the MFD work?(muti-function gauge). If it does, is there any red light blinking? it shouldn't be.. sorry for all the questions, the more we know, the better someone can help you.

  3. #3
    It was inspected and rebuilt by a local powersports shop. All the grounds are good, batteries brand new, timing is spot on fuel lines are all new along with the tank.

    With that said I finally got it running right, i pulled the carbs yesterday and found that there wasnt a fuel restrictor in the return line and the pilot jet had a small piece of brass in it. I just ordered new filters (oil and gas) along with a triple outlet pump.

    Currently i feel i still have a problem, after a few heat cycles yesterday I pulled the plugs and they looked good (not running extremely lean or anything) but the front and rear cylinder were getting pretty hot so I decided to call it a day and look into what could be causing that before I damaged the engine any further.

    Could it be the low output fuel pump not getting enough fuel to 1 and 3 or are my carbs tuned wrong? I have the low and high speed needles turned out as the manual says for a 93 750.

    Thanks for all the help.

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