Polaris ultra problems

[Sled101]

i have a 1996 polaris ultra and i cant get one of the cylinders to fire, it has the same compression as the other two, it is getting fuel and i have already replaced the carb and plugs. it will run but runs rough and wont idle. looking for help or ideas to fix it. Thanks
-Sled101-

 

[BB454]

680

Clean the carb. Look at the idle jet, I'll bet it is plugged. Seen this a lot this year. Also just to make sure, look at the coils. There is a common ground strap on them and I have seen them break and cause rough running or no run at all.

 

[Sled101]

ok i will look at that today thanks for the help

 

[DanB]

A couple of additional suggestions.

1)Checking the coil. The positive leads on the coils are numbered and use bullet terminals. This makes it easy to swap the input leads and spark plug leads between adjacent cylinders in order to maintain firing order. You can then start the motor and see if the problem stays with the cylinder or follows the coil.

2) If you still have a problem after performing the above test and the tests suggested by others, I would inspect the reeds for that cylinder. If you've got a faulty reed petal you can also have the symptoms you describe. You can run a test to see if this might be the problem. Pull the airbox and start the motor. Blip the throttle and look at the air-fuel "mist" that blows back through the carbs (there will always be some). If the blow back through the bad jug is noticeably more than the others then you've got a bad reed.

 

[mike_s]

A couple of additional suggestions.

1)Checking the coil. The positive leads on the coils are numbered and use bullet terminals. This makes it easy to swap the input leads and spark plug leads between adjacent cylinders in order to maintain firing order. You can then start the motor and see if the problem stays with the cylinder or follows the coil.

2) If you still have a problem after performing the above test and the tests suggested by others, I would inspect the reeds for that cylinder. If you've got a faulty reed petal you can also have the symptoms you describe. You can run a test to see if this might be the problem. Pull the airbox and start the motor. Blip the throttle and look at the air-fuel "mist" that blows back through the carbs (there will always be some). If the blow back through the bad jug is noticeably more than the others then you've got a bad reed.

The ultra ignition system has no firing order per-se. all the coils receive the same signal and fire at the same time. you can cross the spark plug leads and the engine will run just the same. there could be a coil grounding issue, however. check on that. also checking the carbs is a good idea, you might as well go through and clean them all while you're at it. This new ethanol fuel doesn't store well, and tends to gunk them up more than the older fuel we're used to. Checking the reeds is also a good idea. if the engine has many miles on it there is a good chance that one or more of the petals could be broken or frayed. if you do take the reed blocks off, go ahead and look into the intake throughout and see if you can see a broken piston skirt as well.

 

[DanB]

> The ultra ignition system has no firing order per-se. all the coils receive the same >signal and fire at the same time.

While that may be true, there are three individual lead wires coming out of the CDI with each of these being attached to a different coil. Swapping the positive leads at the coils and swapping the plug leads will assist with isolating a CDI or coil problem. For example, let's say the center cylinder isn't firing. You swap the positive leads between the center and pto , and to keep it kosher, you also swap the plug leads. If the pto cylinder quits firing and the center jug starts firing then the center coil is suspect. You could also conclude that the center carb and intake are OK. If the pto still fires and the center still doesn't, then it points the finger at the CDI or a problem in the intake, but it also exonerates the center coil.

Mike, also, welcome to the forums. Nice to have another "triple head" around!

I read one of your other posts and it sounds like you and I have done some similar mods to our sleds.

Mine is based on a 96 bulkhead, and there's not much left on it that is "stock".

My current motor is based on a 97 bottom end with a 900 big bore kit (originally from HTG - 76.25 mm bore) along with HTG pipes and a Dynoport can.

I converted it from round-slide carbs to the 38mm XCR VES motor rack-style flatslides. These carbs need very little tweaking and are much easier to live with than the individual round-slides.

I also use a Holz rear suspension but with a 156 track and a Fabcraft tunnel equipped with a custom U-cooler built by Holz. A Tison rolled/extended chaincase was also used.

The front end uses custom home-made radius rods because I run a 37" stance, spindle to spindle, with Simmons gen 1 skis.

Seat/tank is a modified stock unit that's had the rear pan cut off and replaced with a custom light-weight seat.

There's lots of other little things that have been done, but that's the bulk of it.