My 400 will do 55mph. A buddy I ride with has a 99 non-HO sp500 and we seem to be equal in just about every respect.

 

IM sorry, I talk In circles at times@[img]i/expressions/face-icon-small-happy.gif[/img] I meant drop the main down a size. You May find it necessary to raise the clip on the needle a notch or two also, (which will also lean it out a bit) but start with the main You may not have to do anything else to it.. For SOme reason, Polaris upped the main Jet on these machines for 04 without making any other intake changes to it at all! Its really simple to do, wont take but about 20 minutes or so.. NOTE****
Make sure you replace the dang brass screws on the bottom of the float bowl, because they bite and will strip VERY easily after you do this a few times, you can get good 4mm screws from Home Depot for aboout 30 cents.

I need to shim out the secondary, as my belts slightly mis aligned, but when Properly Aligned I can hit about 62 MPH
Right now Im only hitting about 55-57.

 

I just experienced that first hand over the weekend. My carb on my 400 has been giving me fits.

 

Since it seems alot of you are having this problem, I'll post some pointers that I wrote up on the NC site for anyone not familiar with the Carb and wishing to attack this on your own.. it really is a simple procedure, Hope this helps


I was having some jetting issues with my 04 400..Upon first attacking the carb, My Clamp was turned upward so that in order to get to it, I had to take off the bumper, grill, racks, front plastic and Tank. I th ought Id throw a couple of pointers out there for anyone wanting to tackle working with your carb, Im sure many,many of you have done this many times, so if I leave something out, then please feel free to add. This is more for someone looking at their carb and going ..... HUH?
Now, IF your clamp is turned properly, then you should be able to simply Take off the left side panel, reach through with a long phillips screwdriver and loosen your Clamp. Make sure you get it good and loose! Now, some people dont do this but I do it because it makes things a bit easier.
Remove the 2 Bolts holding on your Airbox, then loosen the clamp connecting the Snorkel to the Carb from the Air box. Pull the snorkel off of the carb, and On mine (4 stroke) I tuck it down in behind the Starter, it stays put there and is out of the way.
Next, pull the Clear Vent lines, and the Black fuel lines off the carb.
Dont worry about the Choke and Throttle cables.
With this done, you should be afforded decent access to the top (slide, needle and clip) and the Bottom (main, and Air screw).
SOme things youll want to do, If your adjusting your needle, or installing a Dynojet.. Then youll need to take the Brass plate off the top of the Carb.
First loosen the 4-4mm phillips head screws on the top. Be careful when taking them out as the spring inside is under pressure and will fly if your not paying attention. Now, when you have these 4 Brass screws out, the first thing you wanna do, is---- THROW THEM AWAY. They are Junk, strip easily, and without a set of needle nose vice grips, could leave you without the ability to make any trailside adjustments.
I got 4mm Screws of different lengths at Home depot that offer a deeper grip and broader head for the screwdriver.. MUCH better , Cost.. 33 cents.
ANYWHO.. as you pull the slide up, notice the needle hanging out the bottom, be careful not to bang it around on anything and careful how you lay it down.
Get a nice WHITE towel or shoprag and lay it out.. DO NOT STAND over rocks, grass or anything else while trying to remove the clip from your needle. It will surely fall and youll be SOL.
after carefully removing the clip off the needle, Move it up to lean out, move it down a notch to richen up. (Im assuming that by being to this point already you have done a plug check and such to tell whether your running lean, rich, etc..) now the needle will control throttle from not quite 1/2 to about 3/4 throttle. Keep this in Mind, HOWEVER.. It will also affect the main jet (3/4 throttle to full).
Once you Have moved your CLip up or down, make sure that (if you moved it up) the plastic spacer underneath the clip moves up and is flush with the bottom of the clip, or else it wont change a thing. Mine was Stuck to the needle and took alot to get to move without tearing it up. Reinsert needle into the slide, and put the plastic washer on top for the Spring. When Reinstalling it into the Carb, pay attention to the rubber gasket around the Slide, it has an "ear" on it, that goes in a groove on top of the carb, this assures you have the slide installed correctly. Remember to Use NEW screws when reinstalling the brass plate.
Now that the Midrange is done, turn it over and remove the carb bowl. Again, throw out these worthless screws and replace with a quality screw..WHen removing the bowl, pay close attention to not damage the Floats when the Bowl is off.. try not to let it bang against anything, and try to make sure its around no dirt or mud.
Youll see the Main Jet on the bottom of the Carb, between the floats. Remove and either put a larger in, (richen) or smaller in (lean) depending on your needs, (again which im assuming you already know based on the machines performance).
Reinstall the Bowl, and your good to go. Sometimes very subtle adjustments can be made with the Airscrew. On the newer Carbs its under a Brass plug on the bottom of the carb, that first must be drilled out to reach the slotted screw for adjustment.
Now, alot of people just always go to the main, if its rich, lean, whatever, But as I said, the setting of your needle WILL affect the main and how your machine transitions to full throttle running .
If you have jetted the Main, and its now showing good Color on the plug, but your still having a slight bogging, try leaning out the needle a notch.
WHen reinstalling the Carb, switch the carb clamp to the right side of the machine for easier access next time. COnnect your Hoses back up, and be sure that when you tighten th clamp for the boot connecting the air snorkel to the Carb, DO NOT OVER TIGHTEN.
I actually leaned my Carb out, and put it all back together and it was running even more rich then before. The Culprit? I was in a hurry and cranged down the Clamp on the carb/air boot and collapsed it part way restricting airflow. So Be Careful.

ANywhoo, after this, youll more than likely end up having to do it again until you get it where you want it. But after a few times, Youll get faster and faster and taking it on and off.. ( last weekend I had mine off and on about 9 times in less than an hour , playing with Jetting)

It's Not Intimidating, But do expect to make more than one adjustment.. Usually when you get one end of your rpm range dialed in, it usually shows the jetting flaws of the other end of your RPM range.

Performed on an 04 400 sportsman

Ron

 

ktmguy, thank you for the advice.[img]i/expressions/face-icon-small-smile.gif[/img]

 

Not a problem, hope it helps!

 

Good info from ktmguy70!

Another thing on the SP400 carb. The idle mixture screw is misadjusted at the factory. Mine was at almost 4 turns and I believe the owners manual says it should be 2.75 turns. In the end I think I left it at 2-1/4.

While you can get it to run properly by changing the main jet and adjusting the jet needle, my recommendation is to buy the Dynojet kit. You get a recalibrated jet needle and a set of main jets to cover every situation. They claim it makes 3HP and I believe it. Mine runs soooo much better. Well worth the money IMO.

Another thing for the guys at higher altitudes. Change the shift weights in the drive clutch to the 20-40 (per the owners manual). It makes a big difference.

 

Yes I agree, go with the dynojet for optimum results, It made a difference in mine also. But a simple drop in the main WILL solve the problem, it depends on whether your satisfied with it or not..

I also Agree with the weights, although I actually went with heavier weights when I added the heelclicker and put 1.2 in the shoulder, Im very happy with the results, but I seldom ride above 2,000 feet and 90% is at 900' or below.

You guys couls also just through in a White Primary from polaris (again about a 20 minute job) and really be surprised with the results!

 

ktmguy -

I tried the Heelclicker kit, but at the elevations I ride (5000-10,000) it flat killed my midrange (lowend was awesome). Hows it working for you overall at the lower elevations?

 

I've had great results from it. Belt grip is incredible, I was able to hook to a tree and spinn all 4 tires in high range without slipping. I have Played with mine a bit, but dare not add anything more than the 1.2 on the shoulder for the little 400.
With the Stock Primary, I had low end that was incredible, basically the weight of your thumb could cause the thing to climb the tree, IF I remeber I was engaging around 1200 RPM which is right above idle for me. While the Low end was great, the mid range was terrible, However I chose to ride like this for a bit in the tighter woods and was very happy.
I changed out the stock blue/green to a white primary when My wife and I headed into the mountains for some riding, as there was going to be more wide open places. I picked up about 200 rpms and the mid range improved greatly as well as top end with hardly any sacrafice to the bottom end, engagement was around 1550 rpm. Im now running the Orange for Fun, ENgagement is around 1900 rpm, But will probably be a bit higher when I take the time to Shim and get some of the drag off the belt. WIth the ORange Im very happy, midrange is where its at with the orange primary.
Coasting along at 15-25 MPH and nailing the throttle and you are really taking off. Ive lost a little bottom end, and Im now running top end rpms back around stock *near 6400 RPMS* and I'll probably have to richen the main a notch if I keep the orange in there as I was Borderline when I was running 5750 rpms.
All and all Im very happy with it, As we al lKnow this little 400 can use all the help it can get!
Im sure at the elevations your riding, the lack of air really hurts, and trying to spin any extra weight on the clutch even further hampers you. Did you try any different primarry springs?