600 vmax snowmobile on a Joyner dirt devil

[Haskellbud44]

I have finally finished my dirt devil buggy…well mostly. I installed a 1994 Yamaha vmax 600 snowmobile engine, with both rebuilt clutches, inside a 2006 Joyner Dirt Devil. I’m trying to figure out the right clutch settings. The buggy is slow off the start. It’s not the carbs. The engine rpms are’t high enough to get the hp to leap to life when on the road. I’m still trying to figure out the rpm gauge, so I can’t speak to the specific values. Belt tension is perfect. Once she gets up to 15-20mph, she can fly like a demon. I’ve had my phone gps tracking speeds at 55mph, and I’m not at max yet. Her rear end starts to break away on the gravel, so I don’t push it any further. I’m happy with the top end rpm’s too. Sounds about right if you get me. I bought three new primary springs, all three incrementally increasing in initial force. I plan to receive soon and will swap them out to see results. Don't recall the weights. The secondary is setup as stock. Not sure how to go about fine tuning that. Any recommendations in general for how to get the engine to start out quick?

 

[bob58o]

You sound like you are on the right track by getting primary clutch springs for higher rpm engagement. Not sure where the engagement rpm is now, but another 1000 or 1500 rpm at clutch engagement will probably help. Like 4500 RPM or so instead of 3200 RPM. Might need some big tires for traction.

 

[panchothedog]

I don't know anything about snow mobiles, but if the clutches work similar to the 30 and 40 series torque converters for go karts, your problem solver might be in the mail. What I'm saying is that heavier clutch springs ( and lighter weights ) can make all the difference in the world. Especially on initial acceleration. Much more than one would think. I've had it seem like the engine got a 20 to 40 percent horsepower gain. Watch for the Postman.