ok guys here we go. first my goal is that we walk away from here with a good understanding about clutching and its components. lets say you have already went through your sled for general maintenance, track alignment, chain tension, and track tension.

now lets start with the primary clutch.

the primary clutch has the wieghts and a spring, the wieghts shift it up and the spring shifts it down. it is an rpm sensing clutch that means all it reacts to is rpms.
lets build a theoreticall kit, the parts and rpms are just for example but i will try to be close.

I went up town and bought a used 2002xc700. I am going to show up my buddys 800.
I look at the stock wieghts and see that they are 60 grams with a lot of wieght at the pin and the middle, than gets thinner as we move to the tip. I go and put in some 62 gram wieghts with more of a straight profile, lots of mass at the pin but it doesnt get thinner, now this is wieght profile, where the mass is in the wieght, is where it will pull harder, as the stock wieght tapers off so does the pull, on the new weight it has a straight profile so it will pull the same as the other but since it has more mass at the tip it pulls harder on top end, now we add in the extra 2 grams of wieght, the engagement stock was at 4500, now it is closer to 4200, we take it out for a run, punch it starts to spin for a second than can barly get moving and lugs around 7000 wide open instead of 8200. the wieghts pulled the rpms down because they are making the clutch shift up faster. We go the the book and our stock spring is 140-330. what this tells us is that at engagement the stock wieghts overcame the force of the 140 lbs of spring force at 4500 rpm, but the new wieghts over came the spring at 4200rpm, same at wide open throttle, the stock wieghts with 330 lbs of spring force made a shift rate at 8200rpm, but the new wieghts overcame the spring at 7000rpm.
so now we get a new spring, so lets try a 150-350. lets say this now gets us back to the 4500-8200. but now our rpm are the same but it should be pulling a little harder with a pile of more top end pull.
so you can see that if you just change one thing it totally changes everything.
you can also see how the wieghts open the clutch, the more wieght the faster the clutch opens. thats were the primary spring comes in, once you have your wieghts, just get a spring to set engagement and help set wide open throttle rpm.
lets just stay on primary and see what i didnt make clear enough. then after a couple days we will move to the secondary.

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ok i understand that but what if your talking radar runs where you dont want a high engagment but more top end. also what would happen if for say you had stock 58g and you kept the same weight and changed where the weight was dispalced on the weight.would you just make a fine spring adjustment and still gain more top end. this is going to be some real good knowledge for me thanks madcow.

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if you left every thing else stock but went to a more aggressive 58g you would have some gain.
for speed running you want to bring that engagement down low so you would get like a 100 330 or 80 =280. for speed running I have found that with all else the same just bringing down the engagement has increased speed. i use a polaris gold with 62-66 grams she comes on at 2800-3200. If you are looking for serious gains for speed running you have to regear for the speed you want to hit. lot of chassis tunning and then I like to set up the primary clutch to pull the rpms down and engage were I want, then i use the secondary to get to the fine tunning, i run a helix with several spring to see what the speed and rpm are doing and go from there. the less helix and less secondary spring the faster you will go.

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so if i have a 120-310 with 10-58 weights i should be looking for like maybe a agressive 64g weight and a 78-240 primary spring and if gearing is 23-39 i should go to like 25-39 or what im getting the clutching what about the gearing should i go up on the top and go down on the bottom or should i just go up on the top.