Last time I took my wifes 2000 trail boss 325 to the mountains it barely ran. It had to be the jetting for altitude because it was fine as soon as I got home. I've got two questions, since I've looked at the bike from both sides and can't actually see the carburator because of the plastic, how hard is it to change the carb jetting? Also, does anyone have any idea about what size jets I should start with for about 7000 feet?
Thanks for any help.
Max

 

Main jet should be all you have to change and maybe make an adjustment to the airscrew. What main jet are you currently using and at what altitude are you at now. To adjust the airscrew you probably only need to turn it ccw about 1/4 turn to 1/2 turn. If your case you have a gas screw, you need to turn it cw about 1/4 to 1/2 turn. Oh what do you expect the temp to be where you are going? The reason I ask all these questions is that I have a tuning guide that I can tell you what jets you need to be running for the temp and altitude you are going to.

 

This bike is totally stock, I've never been in the carb or had my hand on a manual that would show the stock jet sizes. I figured someone might have that information in here. I'm hoping the temperature will only be in the upper 80s at the times I may be riding. Altitude will be around 7000, maybe a little more. I forgot my GPS last time I camped in this area so I can't get to precise about that. Your tuning guide sounds like just what I need for these answers. Is that thing specific to Polaris?
Max

 

It is specific to Mikuni carbs which are used on Polaris's. Alot of places sell the guide, it is only a few dollars, I got mine at www.aaenperformance.com What altitude are you at currently? Your main jet should be a 142.5 or a 145. If you bought your machine new, you should have gotten a supplement sheet that tells the jet size you are running. Mikuni recommends a decrease in 1 main jet size for every 2000 ft above your current altitude. If you can find out which jet you have and tell me what altitude you are at, I can tell you exactly what jet is recommended. Thanks

 

OK the elevation in Phoenix is 1090 feet. I'm at work on the computer so I won't be able to get back with you until Monday with the jet size. I did get the bike new so I'll just have to dig out the manual. I hate looking at that thing though because it covers what seems like 15 bikes instead of just the Trail Boss. It's confusing as hell trying to sort out what applies and what doesn't. When I changed my tranny fluid for the first time I overflowed it all over the skid plate and the floor making a huge mess because I misread the manual. I don't think Polaris made any friends by getting cheap on the owner's manuals that way.
Max

 

Yes, I have to agree that Polaris manuals are the worst there is. I saw a Honda manual not long ago, and it was as good as my repair manual for the Polaris. I was very suprised and disappointed at the same time in the lack of instruction of the Polaris manual. Oh well. With you going to that high of an altitude, you may also want to change your weights in the Primary. Right now you should be set-up with a 10RH, for that altitude you could drop down a few grams. I will have to get back to you for that number of the weights you would need.

 

OK, I looked in my clutch book and your weights are not listed. The best thing you could do in my opinion, would be to call your nearest dealer or do a search on Polaris's page, and find a dealer in the area you will be riding in and find out what kind of jetting and clutch weights they use for your machine. The weights are not very necessary, but wiould probably improve performance a little.

 

Sorry I didn't get back to you earlier. I'm spending all my free time now fighting my pool company to fix my chlorinator. I never got the original jet sizes yet. I was wondering what you're talking about with these 'weights' though. That's a new one on me. Does it have something to do with the springs in the transmission and belt assembly. I've never gotten around to studying the Polaris tranny yet, it's the first one I've ever owned. I bought it mainly because my wife never has been able to get the hang of shifting even with an automatic. The Polaris is great for her and I enjoy putting around on it too, I just don't think of it much as a 'sport' bike. When I want speed I hop on my Yamaha YZ400 and hang on. I wish I had more time to tear into it though. I've read you can change clutch springs to wake it up some but unfortunately I haven't seen very much on the market for the Trail Boss as far as performance parts. I think what this thing really needs is a good exhaust. Anybody could just look at the stock unit and kow there's no way the motor can breath very well.
Max

 

Aaen has some performance parts for the 325. Hot Seat Performance also has a spped kit for the 325. I am sure there are other's also. The weights are part of the clutching for the Polaris's. Here is an exploded view of the driven clutch and the weights I mentioned. They are #9 on this chart. Some changes can be made to the clutching for gains in performance. Most speed kits will come with clutching that compliments the rest of the package.

 

Is this clutch classified as a torque converter type or a centrifugal (sp?)? I can see where the weight size will make a difference in clutch engagement as the rotational speed increases.
That speed kit looked pretty slick. I thought it was a little pricy until I started looking at all you get and then I thought maybe it's not so bad. I liked that muffler more that the megaphone unit because it came with the spark arrester already in it. If you're not riding on private property or a closed track you've got to have that these days. I guess if you put all that on and magically shaved off about 200 lbs (dream on), the bike should run pretty good. Thanks again for staying on top of my posts. You've got more information than I could have hoped for.
Max