Ok.....Some of you may have seen a previous post about an 01 Trail Boss 325 that I have been trying to get running right. It had 120 main jet in it and just didn't seem to have good power after about half throttle so I looked on the Polaris parts look-up web site and it said that it was supposed to have a 145 main jet in it so I proceded to my local Polaris dealer and got a 145 main jet and installed it and this thing would not run with the 145 in it, if I took the air box lid and air filter off I could make it run but not very good(It ran better with the 120 main jet in it), I think Polaris made a misprint in their parts catalog. Any way.....I have now put the 120 main jet back in and have it running pretty good with some fine tuneing, It runs great up to about half throttle but after that it just seems to quit making power, it just kinda flattens out and seems like it should pull harder and go faster than it does, is this just the nature of the beast or is there another problem going on here?

I am starting to wonder if I should drop down another main jet size.

Oh....one more thing, I have looked on DynoJet's website and their jet kits for this machine show main jets ranging from 144-160. I wonder if they have actually tested these jets in these machines or if they are just going by what Polaris says is supposed to be in them?

Here is what has been done so far:
Checked compression 150-160
Cleaned and adjusted carb(needle clip in middle notch)
Replaced needle and seat in carb
New air filter
New spark plug and cap
Drained and cleaned gas tank
Checked timing
Pressure tested cylinder for valve leakage
Adjusted valves
Replaced secondary clutch buttons

Any input would be greatly appreciated.

Thanks in advance, Caanan

 

Come on guys give me some input on this machine.

Am I chasing a problem that is not really there?

Am I expecting too much out of this machine?

I ran it today with my gps with me and I finally got it to top out at about 38 MPH but it just seemed slow getting there.

Thanks, Caanan

 

after i did the 414 big bore in my trailboss i put in a 150 main jet. not that i know what i'm am doing but maybe it is too much for a stock 325. or maybe some of the other screws need some adjusting to get the mixture right. just some thoughts from someone that doesnt know much about carbs.

 

Thanks for the reply Spiffinmaine, So how did your trail boss run before you put the 414 kit in it?

What was your top speed and how fast would it reach it?

What size main jet was in it before you put the 414 kit in it?

This machine had a 120 main jet in it when I got it and I have put the 120 main back in it now after trying the larger mains because the larger ones made it run worse.

Thanks, Caanan

 

If it's running right , you should get up to about 50.

 

Your Mainjet Only effects from 3/4 to full throttle your needle effects from about 1/4 to 3/4 throttle your pilot jet effects from 0 to 1/4 and your mixture screw effects idle. you should be running a 145 mainjet anyways my friend has one and that is what he runs with no problem
your problem lies somewhere else. I would guess checking your air hose from your tank make sure it is not plugged or kinked and also check your petcock from your tank make sure it is opening up and letting a steady stream of fuel pull your gas line off of it make sure it is coming out full bore they have a habit of stripping and not letting enough fuel out. check your choke too.

 

Thanks for the reply Alpine2, "air hose from your tank"? Are you refering to the air intake to the air box or the gas tank vent hose? If so both are clear. As far as it not getting enough fuel I believe it is gettin plenty because when I put the 145 main jet in it is so rich that it will not accellerate with the air filter and air box lid on it. If I remove the air box lid and air filter it will run somewhat better but is still way way rich. The choke seems to be working properly as well, the adjustment on it at the carb end is adjusted all the way in.

Any more thoughts or things to check.

Thanks again, Caanan

 

Slide needles and nozzles are really bad about wearing out on about all Polaris ATV's.

If yours is worn no amount of tunning with your jets will make it run correctly.

They will run EXTREMLY rich with the stock jets.

Replace your slide needle and nozzle and go back to the stock main jet and make sure your airbox lid is on and all the filters are in place.

 

Thanks cornbread , when you say slide "Needle" do you mean the main jet needle? And when you say "Nozzle" what are you refering to?

Here is the link to the Polaris Parts lookup, It's a 01 Trail Boss 325

http://parts.polarisind.com/Browse/Browse.asp

Thanks, Caanan

 

Does yours have a CV carb ?