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Discussion Starter #1 (Edited)
Recently purchased a 03 Sportsman 400 for the misses.I know the 400 is no powerhouse,fine for her.I don't like how the clutch engages.Takes a lot of throttle to get going.It has only 800 miles on it,belt is like new.Hardly any wear,measured it.The machine is stock also.No oversized tires.Would like to change that so it engages sooner.Plus a little stronger.Also don't want to loose top end speed.
 

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When you say sooner, do you mean sooner as in RPM's need to be lower, or that you want the ATV to take off harder from a start with less throttle?

I am using the EPI PATV1 red spring on my Sportsman 500 HO with good results. I believe it should work for your 400 as well. It raised the engagement to ~2200rpm and upshift to ~6700rpm on a factory machine. This spring has a rate of 35/140lbs.

Factory it looks like that 2003 400 has 10BH weights which are 47G and a Blue/Green primary 0/110 lbs (same spring as my 500HO), so the engagement and shift behavior should be similar.

The 2200rpm engagement may be a little high, so you could look for a spring that has a lower start rate (2.5" weight measurement) the EPI PATV9 25/135 lbs may be a good substitute if the engagement is too jerky.
 

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In that case, I would try the PATV1 spring. Do some searches, it has been highly recommended. I believe your clutch is engaging too early causing the engine to be far out of the torque curve. The engine needs to overcome those initial RPM's before reaching peak torque.

Again, remember that Polaris builds these ATV's to suit a variety of conditions and rider ability. A higher engagement may give the ATV a more aggressive take off, but could be too abrupt for some riders.
 

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A spring alone isn't going to give you a harder engagement with less throttle input. The start rate on the spring is what determines the engagement RPM of the clutch. Lowering that number will lower the throttle input needed to get moving, but will also soften the engagement without weight modifications. That in turn will make if fell weaker off the line as the engine may be below it's power band and struggling to get you moving.

Raising the start rate will require more throttle to get the RPM up to get the weights to close the clutch and engage the belt. That will make it take off harder and feel stronger, but the trade off is normally a harsher feel to the engagement. And it does the opposite of what you want it to which is give more throttle to get going.

The higher RPM engagement that you are experiencing is normal to Polaris and if this is your first one it will take a little getting used to. They are a different feel than a Yamaha or Honda that many are used to. To get a lower RPM engagement and a harder launch you will need to change more than just the primary spring. You will need weights and possible some secondary parts as well.
 
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