Before you start throwing weights and springs around, pay attention to mechanical details.
That clutch is very sensitive to harmonics and vibration feeding back from the driven components.
Start by facing your clutch. Cut just enough but don’t leave anything that can cause your belt to dance
around. This nice even face allows all else to happen. The weights and roller arms must be machined to
remove all slack. Arms that can flop about can snag. Get your arms nice and tight and dead center.
Double check your fiber Hex bushings and make sure everything is absolutely centered from component to component. Every part must hand off power and must be at 90 degrees to be efficient. If you bend power, side load will rob you. The outer cap can be substituted for a longer bushing model.
At idle and low speed some shaft is a bit deep in the bushing but at any speed at all you are on the longer bushing and it helps.
Our last set up
- green El Tigre spring
- faced off sheaves
- new bushing set (one long one short)
- comet pins in arms
- big rollers (small rollers may shift a bit harder but may lose shift force at the top)
- no weights added. (you may need to add or take off weights for your RPM range)
- stock roller bolts and nuts
- about 7000 RPMs
- 173 ramp
- .04 inch clearance, 2 ½ inch deflection with secondary closed, belt up top
- soft set (9 lbs.)
- stock soft spring (black thin)
- you must make sure your belt is up all the way. Don’t jam on the brakes at the line, roll up easy and coast to a stop.
- 9 to 11 lbs.
- stock spring
- set it up to back shift going into corner and coming out of the corner about 250 - 500 rpm over revved. That way you come out of the corner with your clutch singing and falling right onto the peak power for the straightaway. A bit of the trick is in a sled that doesn’t bind up. You need a little drift in the back going in that will tighten up as you get on the throttle. Set your front arm to give traction but not lift when you get on it coming out. For drags try to gear so you are pulling all the way, but not pulling down. Gear so you don’t lose you pull about two thirds of the track. Too low will do that. 1.95 to 2.00 works good on ovals 1.80 to 1.90 is good for loading a drag sled. Maybe lower if you have a real torque monster.
To end up being a quick sled a lot of advanced preparation is required. In the old days of Yamaha factory support, Bob Work , the race director told every one the same thing,…“don’t call me until your sled is blue printed”. He meant starting at the front and taking all the play out of your steering -suspension and be sure your carbides are set dead straight. Measure on the cutting edge and align your blades perfectly. Place a long straight edge along the track and protruding out front past the skis. Set your right hand ski dead square with the track and then your left ski off the right. Now you are rid of any side loading and the front won’t ‘fight’ the back.
When you are sure everything is lined up and sliding freely over the ice, move on. Align your engine and level the clutch in the chassis. You want it straight back and straight up.
Move to the secondary and do what ever to align its faces with the drive clutch. Shims and slots will help. Get the chain case lined up in both directions and move to the drives. Square off your drive shaft to the previous clutches and casings. Now run some straight edges back from the driveshaft and get the skid frame in absolute square to the haft and not binding in the tunnel. Run only enough track tension to avoid ratcheting. Work on it until you can pull the whole drive system through with one finger and thumb. The more free it runs with the least resistance possible is the way to go. This is free horsepower. Anybody can port or pump up an engine but the truly fast guys take advantage of free power and try not to have to use radical modifications to make power. Dependability is a big factor if you race 15 lap events.
You see now why blueprinting can give you an advantage especially when the fast guys show up. If your sled is the most efficient it can be, and your motor runs strong and clutches are clean and working, you will be hard to beat with a less prepared sled.
Lastly, don’t overdo the traction thing. Use only enough pics to get a decent launch and only enough carbide to turn. We use about 150 pics and 6 inch left to 8 inch right of 60 degree woodys, sometimes going down to 4 and 6 on the blades frees you up for more straightaway speed. Use only what you need, any more is just a brake. What you press into the ice has to be pulled out of the ice on an angle that eats power. Carbides that shave sideways also eat speed and will dart around going in.
Keep it smooth, dead straight and running frictionless and your whole package will be quick.
Check out more of Gords great submissions here.