I have a 400 Xplorer & my brother a 400 Xpress. If (when) we race, he just barely outruns me. If I can talk him into hauling just 50 or 75 pounds of stuff, I can just exe past him at a snails pace. Both machines are stock & I assume his is a hair faster since it is strictly a 2wd. Now here is the kicker. I know another guy who has (actually had, it is gone now for a new machine) an Xpress also. It appeared stock, no pipe, reeds, or anything we could tell done to it. But he would just smoke by us, laughing all the way. His acceleration wasn't much better if at all until about 35 or 40 MPH, then he would start to leave us. Finally found out what had been done to it. He bought it used from a guy so it took a while to figure out. He had changed to a white primary spring which if I understand right, gives better acceleration with little or no loss of top speed. Then, he put a 1 tooth larger front sprocket, which gives more top speed & less acceleration. The spring & gearing changes canceled each other out, but he had a good 5 to 7 MPH better top speed than the two of us. 65 was pretty easy on any long, flat stretch for his atv. I decided now I want to try it with my Xplorer. I talked to Rick Ritter yesterday & he said, in theory at least, it should work like I think. I will start with a white spring & even try green, just to see what they do, then go with a different sprocket. Will probably have to go with a smaller rear rather than a bigger front, but will have the same effect. Both Rick and a Polaris factory rep said gearing the rear end UP will not hurt the machine mechanically, but neither could say how it would affect the way the 4wd will work. I have the shaft to the front, so I can't re-gear it like the rear. Do you guys think it will work like it should or not? I guess a sprocket is only about $20 so I could be a gunea pig but thought if anyone else had already tried it, I might see how it works. I just am unsure how it will affect how the demand 4 will 'kick in'. We have already established that changing the spring & sprocket will gain top speed without really hurting acceleration with my friend's Xpress, but wanted to know if anyone else had experience how it might affect the 4wd. By the way, thanks Rick for being patient with someone who wasn't sure what they wanted when they called. He was very helpful as to which spring would do what & figuring the best thing to try for what I wanted to do, as well as being patient while explaining it to me until I understood what he was saying.
It might take a while before I get all this done (we are in the middle of harvest) but if anyone is interested in the results just say so & I will post a before & after performance results of the modifications. Thanks to all those who are still awake.
Farmr

 

Farmr123,

I will try to help you. The rear wheels on a polaris machine are supposed to turn 1/5 of a turn before the front wheels are mechanically engaged. The front and rear sprockets(factory) should be 13/36, or a ratio of 2.769. That means 2.8 turns of the countersprocket yields 1 turn of the rear wheel. Say you're wanting to go to 13/35, a ratio of 2.692. This would mean a difference of .077 turns less of the countersprocket for 1 revolution of the rear wheel. Doing some math tells me that the change you're looking at will basically have no affect on the awd.

 

Farmr123 - yea, I would be interested in finding out the results. Post them when the crop is in.

 

Factory rear sprockets are available in 34, 36, and 38 tooth.

38/13= 2.92
36/13=2.77
34/13=2.62

By installing the 34 tooth sprocket the top end should encrease by 5.4% all things being equal.

So if your Xplorer ran 56 MPH it would do 59 with the 34 tooth sprocket installed. Unless of course the drive clutch modifications applied more belt pressure and allowed the drive belt to ride further up in the drive clutch sheaves thereby further increasing terminal velocity.

The Fuji 378 2-stroke is very sensitive to carburetor settings. I would start with the air screw adjustment and move it around in 1/8th turn increments until the "sweet spot" is found. A properly adjusted air screw can easily make a 5% difference in top speed.

I know the air screw adjustment is not supposed to have any bearing on top end performance but it does.

You should also verify that your choke is properly adjusted and not enrichening the fuel mixture under normal circumstances. Good luck

Also, to minimize friction in the front drive train, use Mobil 1 synthetic trans fluid in the hubs and Mobil 1 synthetic 75-90 in the front differential. (do not overfill)

Keep us posted.

 

Farmr123,
I can tell you first hand that the green spring will make a world of differance on the way the belt hooks up.I have it on my 00 Xplorer and I keep wondering what took me so long to try it?I also would be intrested in the outcome of your experiment,keep us posted,
Bill

 

If it works for you then it will go into my scram also alittle more speed is always nice and even better when you lose no bottem end. plus i will be putting on a low range pipe from RcR in the near future so that would all but eleminate the loss in bottom end if any. hpefully your findings will work would you need a longer chain also ?

 

I'm sure it will work, the trick will be finding the best spring/gearing combination. A one tooth larger front sprocket is kind of hard to find, so I think I will go with a 2 tooth smaller rear instead. That way the chain I have will for sure be long enough. I figure I will switch springs first to see what happens. We all read what the green spring can do from another post. The Polaris rep I talked to thought a white spring might even gain a couple MPH without changing sprockets, so I will try that first. If it does, I may stop there. Otherwise I will try gearing up and maybe the green. I'll also compare the differences between the two springs. I'llkeep you posted as to what does what. It was raining (can't go on with harvest) but the springs aren't here yet. Clearing up now, so I suppose I'll get a package this afternoon. That's the way it goes. Harvest first, then play.
Farmr