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Discussion Starter · #1 ·
My freinds ultra 680 won't rev above 5500 for some reason. we just had the motor completley appart down to the crank. The carbs are all fine, jetted to slp spec. It has slp pipes. When it was on the stand it was fine, but he took it accrost the grass and it wouldn't get above 5500. He said it spiked to 6000 once for a second and the bogged back down. I beleive it is supposed to rev to 8700? Can somebody please help me?
 

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Carb slide unhooked? Check the compression on all cyl, and check the spark to all cyl. Are all three plugs burning the same? He should not be running it ou tin the field running that low rpm, on 2 cyls, as I am sure that not all three are firing.
 

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Carb slide unhooked? Check the compression on all cyl, and check the spark to all cyl. Are all three plugs burning the same? He should not be running it ou tin the field running that low rpm, on 2 cyls, as I am sure that not all three are firing.[/b]
I had a slide come unhooked on mine once. Thought I hurt the motor so I rode it to the nearest road crossing before I shut it off to investigate the trouble. Middle cable came off, how I will never know. It went a little faster than 25 though.
 

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Discussion Starter · #6 ·
Both the clutches are fine, we are checking the compression tomorow. When He put the carbs together I watched and made shure the slides went on right, but I will take them off and check. We took the motor appart because it wouldn't run right when he bought it. We found out that there was a head bolt broken off, the wires to the electrode were broke, and the nut holding the flyweel on was completley off, the flyweel came off by hand. So it was a good thing we took it appart. I will check those things and give you guys a update, thanks for the replys.
 

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Discussion Starter · #7 ·
Also all three plugs appear to be burining the same. Some of the exhaust is getting under the hood because we havn't put silicone sealer on them yet. Will that cause that big of a probelm?
 

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Out of phase crank can cause some real headaches too....I couldnt get mine to run right and when I sent the crank out he said it wasn't horrible but it would be enough to make it run not near its full potential.
 

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Discussion Starter · #15 ·
Just worked on the sled, still haveing the same problem. one of the carb slides was unhooked, we hooked it back up and made shure was sliding properly. Took the sled for a run and it did the same thing it did before. When he got back in we checked the slide again and it was working like it should. These are the things we have checked:

-clutches are fine and shifting and clutched to slp spec
-pipes and muffler are clear
-carbs slides are opening and closing and jetted to slp spec
-all three plugs are getting spark
-airbox is not cloged
-all three plugs have burn on them and are sparking
-compression is 130, 130, and 125


any other suggustions?
 

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Hey coy120,

Be sure to check the choke cables for slack when the choke is off. This can cause a rich condition.

As mentioned before be sure to check the crank for out of index. The Polaris shop manual has the procedure and it is pretty easy to do. I also think there was a thread on this forum a few months ago that describes it as well.

Good Luck!

Steve


:banana:

PS: The arrows on Fuji motors point to the mag side of the motor......
 
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