I am at a loss and need some help. I purchased a 2001 polaris trailboss 325 about 3 weeks ago. When I got the machine, I knew it had a miss at the high RPM's and thought that a simple tune-up would take care of it. In that I have had some problems, let me be clear about the symptoms...
When going slow, low RPM, the machine seems to run fine. When I get to the higher RPM's and when the machine is under load (climbing hills etc.) the engine will sputter or just loose power. The power drop off is so significant that I think that it may not make it up a very reasonable hill.
-I started with the new plug, clean filter, etc. No affect. What I noticed was that the plug was very black with a two very small white spots on the electrode. (rich conditions as I understand them)
-Since time was an issue for me, I took it to my dealer and told him of the problems I was having. He removed the carb and found the needle jet to be worn. Replaced and sent me on my way. Seemed like it made a small difference, but the problem resurfaced when attacking the next hill.
-Pulled the plug and found the same rich conditions.
-Theorized that it may be a clogged exaust system so I removed the muffler and ran the machine. Still sputtered at the high RPM range. Loud too!

I assume that there is an automatic compression relief valve that prevents me from giving you accurate compression readings.

I am leaning toward either a fuel/carbarator problem or a detonation problem. Does ANYONE know or have heard of problems like this one? I could really use some direction for this. Thanks in advance!

 

I dont know is this a 2 cycle engine that year they way you describe the plug i would say try mixing the gas and oil instead of using the oil tank to mix it sounds like it is mixing to rich and if it is a 4 stroke like my 2006 i would say check the oil and make sure its not over full and spilling into the combustion chamber oh and one more thing i cannt spell to good sorry

 

Sounds like the main jetting may be off. Not hard to fix, just not easy to get to.

Two things, call the dealer you took it to, and ask what size jet they put in. Second thing, where are you riding (elevation wise).

I have an 2000 that I just put a bigger carb on. So I am very familiar with the jetting process for this model. Also have the factory manual if you need anything out of it.

And welcome to the forums.

 

Make sure ALL the vent lines on the carb are clear.
Then set the valves @.006
Check the cam for wear while you are setting the valves.
Clean the carb real good you may be in need of a new needle jet tube
Another thing to check would the secondary clutch buttons these when worn will make it real slugish.
Also try unplugging the rev limiter(pull the blk wire )

 

Thanks for all the suggestions. I spent some time reading and found that some polaris carbs have a condition where the choke sticks in the open position. This seemed to fit all the symptoms in that I didn't need to choke to start and it would run rich and loose power. Took the carb off and removed the choke plunger. It was difficult to remove but it did come out. When I inspected it, the sides were scored up so I replaced the plunger and reassembled. That seems to have fixed the problem. My kids are happy once again.
Thanks everyone!

 

im surprised it ran good at lower rpms where the enrichern was stuck open. it should have flooded out even or just as much down low. glad you got it straightend out.

 

Good to hear you got it running right. [img]i/expressions/face-icon-small-smile.gif[/img]