Here's my problem on my '99 Sport 400L. I told the dealer that I have no power 3000-6000 feet. They told me factory setting was a 230 main jet set for 0-3000 feet & I would need a 210 with 1.5 turns out on airscrew for 3-6k. I went to change the jet, but it already had a 210 in it???

Can someone tell me what I need. I've got the K&N ready to put in & would choose to keep the stock pipe hopefully. I need setup info regarding spark plug, jetting, airscrew adjustments, and a good low-mid clutch kit for higher altitudes.

 

I don't know about your 400 specifically, but I've built and tuned a lot of 2-strokes. Factory
specs aren't a religeon only a guideline. 2 seemingly identical machines might need different jets. Ignition timing is an often overlooked variable. The point is, do your modifications, get it running and do some plug tests. Run it hard, wide open, for a minute or so, after being warmed up, on a good stretch of road where you can really get on the gas. Immediately stop and
pull the spark plug out. If it is tan to grey you are right on. If it is black and sooty you are running too rich, it should have been running doggy, with poor power and throttle response, even
loading up. If it is white, if there are tiny little white or shiny beads, you are too lean, it will have run real fast, reving beyond your throttle position, like it was possessed, and you
are about to melt down your piston... a bigger mainjet is needed. It is not as scientific adjusting pilot screws, or needle valves. But start with the mainjet, use the same procedure to test the mid-range and your needle valve, and then get the idle smoothed out. If you change elevations, you'll need to do it all over again,
especially with 2-strokes. You can go through a lot of spark plugs doing this, but fresh plugs are easier to read, and if something is screwing up, at least you know it is not the plug.
Silly Later, Fourlix
P.S. Your Polaris Dealer can install lighter clutch weights for a nominal charge, or free for a newly purchased machine. This allows the motor to rev higher before the clutch is engaged and really works great at a fraction of the cost of a
hot rod clutch.
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