1996 Polaris xlt sp bogging at higher rpms

[Don 0]

I need some pointers. I have a 1996 xlt sp that I bought last year. Needed carb boots and carbs as the ones on there were in bad shape. Replaced fuel lines from inside of tank to the carbs including pulse line. Was able to ride it last year for a 29 mile ride then parked it after 2 weeks it did not run right. Found crank seals were bad. Changed those out. So sled will do 20 mph but you gas it and lays down. All carbs were set and synced. Replaced coils and cdi Box. Checked stator and that checked out. Changed clutches. Same deal. Swapped motors to a 1995 xlt touring 600 motor with 34 mm carbs. And that sled ran before I took motor. I have 12 inches center to center. 5/8 offset with front and back free play. New Polaris belt 3211042. At 1-1/4 belt deflection. Changed rear helix and spring to brand new 34 degree helix and red spring set at #2 hole. Throttle cable is new and choke works as it should. Idles great and starts 3rd pull every time but lays down like a bog. It doesn’t matter what setting I have it at air screws. Book says 1 turn. I tried 3/4. 1 turn. 1-1/4 turns and 1-1/2 turns. The track is correct tension and chaincase was gone through. Please help with any info

[PolarisCobra 131]

Welcome to the forum. Quiet here these days, but the BS level is really low, which is a good thing. I'm not the guy to give you troubleshooting advice for this problem, but hopefully someone will chime in. 

[Saluda 110]

Real quiet !

[jhwentworth 307]

Just a couple suggestions. The OP said he swapped the motor and has the same problem. Right? Polaris had in-tank fuel filters in many models.  Have you checked that? The fuel pump is powered by a vacuum line from the engine base. A crack in the line will impede the pumping. 

[PRP 0]

Try posting on hardcoresledder.com

AFAIK that is the default polaris forum.  

[Don 0]

Hi to answer jh wentworth. Yes I replaced fuel line inside of tank including the brass pickup with mesh screen and the pulse line was replaced as well. Only thing that comes to mind is the original motor was not set to 12 inch center to center it was more like 12.25 inches center to center. Even with it now being 12 c to c. The belt feels a little loose in the drive clutch but it’s at 1-1/4 belt deflection and I can’t go any tighter on the secondary clutch because it’s set to the 1 position for deflection. And the belt is correct for sled. Even used an aftermarket belt. Same thing. Is it possible to have a new after market cdi box to work as it should under low and mid range rpm’s but not at high rpm’s ? Like it would cut out.  Plugs are chocolate brown but wet when under higher rpm’s 

[jhwentworth 307]

Don,

The Polaris sleds I owned were a bit older than yours, but the general rules apply. I'm assuming that the new motor ran in the other sled, and that the fuel pump is from the other sled.

 

First off, have you tried disconnecting the kill switch and any other electrical safety devices? Does you owner's manual describe any such devices?

Have you looked at the fuel being delivered to the motor? Have you looked inside the chain case? I had a Polaris 500 that had a broken aluminum case wall.

Have you tried lifting the track off the ground on a stand and turning the track by hand?  If that feels, and sounds, normal then start the motor and rev the engine to engage  the clutch, then bringing speed up. There will be minimal load on the driven clutch so it should stay closed. Does it open as RPMs are increased?

 

You asked "is it possible to have a new after market cdi box to work as it should under low and mid range rpm’s but not at high rpm’s ? "  It's possible, but why did you change them?

You've changed a lot of things, and sometimes that introduces new problems.

[Don 0]

I changed all electrical items as a way of eliminating them as the problem. The original cdi box had a orange wire that was showing copper strand so I replaced it. I do have the sled currently up in the air and the drive clutch pulls in about 3800-4200 rpm. Then as you increase rpm’s you can see  belt drop in secondary. Carbs have been cleaned and synced with a unisync tool. I have not disconnected the kill switch yet. Will try that tomorrow. Chaincase cover was removed and chain is in good shape and was properly adjusted by the book. Gears looked good and track does spin by hand. I guess my biggest question would be is how critical is the 12 inch center to center distance between crank and jack shaft   As I stated before the original motor was set to 12.25 inches c to c. I can turn the secondary and belt easily in the drive clutch. As if the clutches are to close to each other. As stated in last post the secondary has an adjustable belt deflection cam on the outside of it and with that set to number 1 it has the correct belt deflection. It is the correct belt for sled. Polaris 3211042. My other question would be is can I run the motor with drive clutch removed to see if problem exists with motor and carbs or if it is clutching?

[jhwentworth 307]

11 hours ago, Don said:

My other question would be is can I run the motor with drive clutch removed to see if problem exists with motor and carbs or if it is clutching?

People seem to have mixed opinions on this, but I believe you'd be OK to run the motor without a primary clutch. The engine won't sound as smooth at low speeds because the clutch acts as a flywheel, and throttle response should be quicker.

To be clear, are you saying that the sled displayed the same symptoms with two different XLT motors? If so, it seems most likely that the problem is external to the motor,  but the XLT had issues with crank bearings and seals, so it's possible they have the same problem. Maybe time to check cylinder compression and crankcase pressure. It sounds like you have adjusted the clutches properly, and the drive train/track is in good shape.

I don't have any good suggestions..

 

 

[Don 0]

I was able to get it straightened out. I went back to square 1. Reclean carbs. Reset them. Adjusted cable and oil cable. Put old cdi box back on. Then changed fuel filter. Put clutches back on and started it. Adjusted the pilot air screws while it was up in the air. Put air box on and took it on the trail. So far so good. Fortunately I live on a culdesac and my back yard abuts the rockingham snowmobile trail. Thanks for all who helped. I think it was the the oil cable being adjusted to much. I usually adjust to run a little richer on oil so that the bearings get lubricated better but may have been to much at higher rpm’s causing it to bog 

[pathfinder 96]

Congrats on your success with the Polaris. As I  was reading the thread I was leaning towards a fuel problem, and actually the oil pump is part of that. A bog is usually the motor complaining that it's getting too much or not enough. Be glad it was too much oil, because the opposite would cause a lean situation that tells what going on by melting something in the motor. 

Hope you have a Merry Christmas.

pathfinder