My friend talked to the tech at EPI for about 30 mins, He work's on quad's as a hobbie,he got both springs for the rear pulley and the front,here's what they told him,the rear spring doesn't really do anything just grip's the belt tighter and will not slip the belt as bad,the front clutch spring ingages the clutch at about 1000 rpm's more than the stock one,they said that the 650 when you nail it it goes to 6000 rpm and stay's there until the belt goes through it's travel, then it climb's slowly until redline about 8000-8500 rpm,with the new spring's ot will turn 6200 rpm's reving until the belt goes through it's travel,all and all it makes the quad accelerate faster and harder through the rpm range,BUT he said you will lose about 3 mph top speed,My friend installed them and ran with the stock Dunlop's,stock it would run 66-67 on the speedo. with the epi spring's 64 mph now, but it does get there faster now and wheelies easier,I may get them for mine......

 

How much did he pay for the set?

 

Stakk, I imagine your buddy is running the Black KSS3 spring for the driven clutch, but what spring is he running for the drive clutch? There are six different springs for the drive. I would really like this information, as this is something I am planning on purchasing as soon as SHE WHO MUST BE OBEYED will let me!!!![img]i/expressions/face-icon-small-happy.gif[/img]

 

I ask him this weekend when I see him, I think he said one spring was like 35 bucks and the other was 20 or 25 bucks, I'm not sure I'll find out and let everyone know, they have the kit listed on their website for like 75 bucks I think, these sound like a good mod to do especially if you have bigger than 25 inch tires.

 

Talked to my buddy today on those 650 clutch spring's, the rear one is the black colored one and the front is red colored,I think you'll spend about 50-75 bucks on both depending on where you order from....

 

Stakk, thanks for the spring info. That is the same spring setup Northarkie is running. The red spring is one of the weakest of the drive pulley springs. It is rated at 27.2kg at 2 1/2" load and 63.6kg at 1 1/4" load. The heaviest spring is the green one and it is rated at 65.8kg at 2 1/2"load and 118.0kg at 1 1/4"load. I would imagine that would raise your engagement rpm considerably, but man, would a guy launch!!!!! I think I'll stick with the black and red.

 

I have 2 springs I need to put in mine, I got them from Mike Penland, the ones he sent were a red one for the drive pulley, and a black one for the driven pulley, ended up about 60 bux. I need to make the roc compressor to put the driven pulley in with. so all in all not a bad deal. I was going to do the Mike P. airbox mods as well, I may use a jet kit, or may not, since I know what jetting requirements I need.

 

Blaster,
a tip for replacing the drive pulley spring, once you get the bolt out of the crank, you may be able to take the 8 bolts or so off the cover and replace the spring, then put it back together, at least that is what I hear from Mike. & I'm going to try that when I do mine in the next couple of weeks., a compressor for the rear is a gotta have..but Red, the local mechanic does it without it..I won't try it..(Mike uses a press)

yep..I editeded this post..I had the driven pulley..not the drive pulley sorrry..my bad..

I got the dynojet kit in today, along with the twin air filter, drive & driven springs, radiator hose to mod the stock snorkel, & a 145 main jet for the rear..I'll either swap stock jets out, or try the dyno jet kit..depending on what the stock needles look like..I kinda wish that it had mikuni carbs though..parts are a LOT easier to come up with for those..I was going to do the mike P mod to the top of the airbox lid..now can anyone tell me what a 140 keihin jet relates to as far as a dynojet? if it is close to the mikuni, i'll be able to figure it out..I'm trying for a homegrown mod here..drill bits, & stock jets instead of a jet kit..

 

Surveyor, you mean the drive pulley, right? I built a pulley compressor already. I made it nice and small and when it is all taken apart, it fits in my quad toolbox nicely. I don't imagine a guy will ever need one on the trail, but you never know. The driven pulley spring swap would be a cinch. I haven't taken my drive pulley off yet as I don't have the puller bolt. Gonna have to get one of those. I'll get one when I order my springs from EPI.