As was mentioned in a previous post - I would say all the 400L Scramblers/Sports are "sleepers" because nobody gives them the respect they really deserve or expects the power they can generate. The secret to drag racing with a Polaris 400 is a good, power braked launch then cut the race off early (like around 60mph). The 378cc pinger is a great mill that alot of people don't know, is a near copy of the famous Honda 250 motor. It has amazing low to mid-range power (37 hp in stock form) and when you connect that to a good clutch kit, they take off like a rocketship. The only down side to that is with the auto tranny, they sign off early. In stock form, the 400 Sports top speed is only 60mph. The AAEN topend pipe and Clutch kit I have installed on mine fixed this problem to a point by allowing the engine to pull more RPMs. I can still only top out at @ 68mph. Polarises don't really respond well to top end biased gearing changes (it "confuses" the auto tranny) and I already have 22" tires mounted. To gain anymore top speed, I would need to get the jug ported and alter the clutch further. The clutches tuning is the key to any Polarises power delivery - they are a fine ballance between acceleration and top end. This is controlled by the secondary clutches Helix's angle, the weight rating of the mainspring and the placement of the springs "tabs" in the various adjustment "holes" that line the helix and sheave. I have my HPD kit set up in the most common adjustment that lets you have a good ballance of top end and acceleration. That being said, as far as the engine goes, when I switched from my low-end biased 7hp FMF pipe to the mid-to-topend 10hp pipe by AAEN, I also mounted an AAEN reed block spacer to help the motor keep some bottom end grunt. As far as the actual racing goes, heres an example of my last go around with a DG piped Raptor. At the line, I rev the motor up to its stall speed and when we decide to go, I drop the brakes. Now, before we go any further, you can't do this all day because you will seriously load up the spark plug as well as stress the whole auto tranny system. You do this rev up for the sole purpose of front loading the clutches thereby cutting down on the trannies lagtime. A funny thing that happens is when I'm going against manual clutched machines, the owners usually hear me reving my motor and they start to do the same thinking it will help them. The opposite is always true - they either botch the cluch drop and bog down or they get a good drop, only to spin their tires endlessly or almost whellie back over and have to let off. That being said, the guy on the Raptor got a good launch and he jumped out ahead of me for about 1 - 2 quadlengths for maybe 50 ft. After that, I got into the meat of my powerband and blew by accelerating away from him until about 50 mph (as read from my TrailTech). At that point I was a good 10 lengths ahead when he started to creep back on me - but - by the time we hit about 60 the race was over, I let off and I crossed the "finishline" well ahead. That Ladies is how you do it on a Polaris. As my friend TimSr is so fond of saying - in the real world acceleration is the name of the game, not the "Top speed" that everyone thinks is so important. In the dunes it might have a little more meaning, but near me in the woods - it means nothing.
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Originally Posted by jacob