no need for me to comment on clutching as its already been said, but I would also look into reducing parasetic drag in the driveline, its makes a large differance in speed.
Oversize wheels in skidframe, all 6 small ones changed to 5.350" wheels and then change the rear wheels to 7.5" diameter ones from a 79 srx440, you will need to slightly grind off about a 1/8th" off the axle spacers as the new yamaha wheels are a tad thinner bearing then the older 79 srx ones. Add a marginal wheel kit to the curve of the rails.
clutch alignment/offset should be spot on perfect to srx specs, and a engine tensioner off a srx should be added.
chain tension should be checked and add some ATF for chaincase lube while you are in there. Adjust the chain tension to have about 1" total movement on the backside of the chain, meaning you can move it with your finger 1 way 1/2" and then the other 1/2". Another thing is if your wanting more top speed would be to gear up to a 23 top gear same as a srx.
next thing is to set up your suspension sag, meaning you want the sled to set in a little bit, this will lower the sled some and reduce drag. You can set it up softly and as long as you dont want to go snocrossing it will be fine if your a big jumping kind a person dont do this.