First off you must remember that dialing a Duster on "kill" will never attain the performance of a 102c or other such high performance clutches. However, a Duster is a huge step up over the old, rusted, iron, worn out steel POS's that came stock on many sleds. some people can't stand them, but for some one lunger classes it is the only option. hopefully, this will give you a better shot at coming home a winner, and tranform your Duster into a respectable primary clutch.
Now to the tuning. The first thing you want to try to get is the duster with the ribbed cover comet pn# 211493A. The ribbed cover ensures the pucks will not slip on the cover face, when you really wind that old motor up. This is especially important on the high rpm single cylinder "race engines" like a sachs "C", sachs SS, rotax 292, and kawi 292. just having the ribbed cover will make a huge difference in the way the duster will perform, and will help get more power to the ground, where it belongs.
You will also want to get a large assortment of duster tuning pucks and springs. changing a set-up is just a matter of pulling the clutch, popping off the cover, and swapping springs and weights. It truly is a easy clutch to tune. Remember with the ribbed cover you will have to buy a special set of pucks that only work in the ribbed cover clutch. If you swap these pucks into a regular duster, you will experience excess slipping and actually melt the pucks.
For one lunger racing you will probably want to contact Comet Industries directly and order a product catalog. This contains all the parts, clutches, profile pictures, and engagment charts you will ever need to tune the Duster.
I think it would be wise to have atleast six of each puck, and atleast one of each of the springs, except the orange spring because that will come with the clutch. This will cost a few hundred dollars for the clutch and parts, but that is pretty much all you need. This is a bargain considering the hell you would put yourself through trying to maintain the original clutch that came with your sled.
The first thing you want to do be for you start tuning, is to to put it on right out of the box and set-up your alignment. It should be pretty close, but checking will give you some piece of mind. this is just a matter of checking offset with a straight edge and measuring device. Once you have figured out how far you are in or out of adjustment, you can add or subtract shims to align the secondary perfectly with the primary, cutting power losses and increasing speed.
Now that you have you clutch aligned, pull it back off, and disassemble the clutch completely. Using 180-200 grit sand paper lightly sand the clutch faces with a circular motion starting from the inside and working out. You should sand only until the lathe machining marks are gone (this won't take long!!!!). After both sides are sanded you can proceed to wash the clutch faces in hot soapy water don't submerge the clutch halves, just wash them with an old rag or towel. Allow them to dry completely, and then you are ready for you next step.
Next put the belt on and check your belt to clutch face clearences. This will make a huge difference on how you clutch will perform, and could be considered one of the most important steps!!! before installing the belt, using 180-200 grit sand paper or a scotch-brite scrubbie pad lightly roughen the contact sufaces of the belt. Don't go hog wild, just remove the glaze. You don't to create flat spots and rob more power. When you are finished wash the belt with HOT soapy water, and let it dry. It may be useful to do this to two or more belts depending on your budget because it will save time later down the line. Once the belt(s) have dried install it and, push the belt to one side, and using a feeler gauge measure how much clearence is between your belt and clutch faces. Each belt can be different, so it is a good idear to measure a few belts at a time and mark how each has to be set-up with a paint marker for future reference. Starting Line Products suggests that each belt should have no more than 0.020" clearence, if it has more you will need to shim the clutch closer with some hardware store shims that are the same size as the area where the clutch stem is. If you can;t find a wide range of sizes, they can be made if you have access to a drill press and a various thickness of aluminum or steel. You will want as many different thicknesses as possible so you have a wider range to fine tune with. Add shims to the under side of the spring, and continue checking until you get it about 0.010" clearence. Also record the how many shims each belt requires with your trusty paint marker again. When you change belts you will want to remember this shim count so you can proper shim the clutch, and take advantage of the maximum belt to clutch face contact. Also, as the belt wears it may be nesscary to reshim for maximum performance or change belts to one of the new ones you have prepped.
___________________________________________________________________
PART #2- TUNING AND SET-UP
---------------------------------------------------------------------------------------------------------------------
One thing that i have forgotten to mention above is that the belt should be lightly broken in for about ten minutes. no wide open throttle, just bump it up and down.
Also, put an arrow on the top what way the belt was broke in. It wouldn't really be worth breaking the belt into the shapes of the clutch faces, if you put it back on the wrong way.
Before you start tuning your duster you want to be aware that this is an "economy" clutch, and components aren't made to very accurate specs. For example it is very handy to have a gram scale and drill laying around to calibrate everything the way they should be. You will be amazed at how far off some of the weights are. Springs are also terrible, and don't hold the correct tension for long periods of time. If you have a buddy with a spring pressure tester, test them all frequently.
Now to the testing and set-up. The duster is the simpliest clutch on the market as far as tuning. You simply have to change out pucks and springs until you have a fast set-up. you have to take into account different track types will require different clutch set-ups. this is where confusion can occur. on a loose or icy track where traction is limited or on the typical one lunger race track, you want to have a lighter weight puck then on a hard pack snow track. This is to prevent track spin, and loss of traction/speed. First thing you have to do is find the best set-up for your particular sled, and go from there. This part is pretty much up to you, since rider weight, suspension set-up, and gearing will have a huge effect on what you have to run and will be different for everyone. Once you have a "base line" clutch set-up you will want to create a light set of pucks for when you experience a track with extremely loose snow or glare ice. This simply is drilling weight off the pucks and experimenting. This again is trial and error testing until you get it right, but it isn't rocket science. At some point you will reach a point where the rpms may become too high, this can easy be cured by dropping the spring down one tension strength. keep in mind this ay screw up your last set of weights and cause them to be too light. in which case you would have to get a new set of pucks and grind them for this spring.
Basically, it is testing to see what is the fastest set-up. here is a cheat sheet for setting everything up, it isn't the best, but atleast give you some idea of what to do.
Spring
high engagement-more rpms off the line, more likely to break traction and spin
(best for hard tracks)
lower engagement- less rpm, not as fast take off, less spin
(best for icy, loose tracks)
Pucks
light- high rpm and higher engagement, less likely to spin because there is less torque from the lighter weights.
heavy- more torque, more likely to spin, lower engagement.
Rider Weight
heavy rider- you will need to have heavier pucks than a light person because the sled needs a little more torque to pull the heavier mass.
light rider- you can have a lighter set-up because the sled is lighter.
For one lunger racing, i would have atleast two clutches handy. one with the heavy set-up for the start when the track still has snow on it, and the other with the light set-up when the track is a glare ice nightmare. Also, having two drivers with relatively close weights would be nice so you only need the two different ones, instead of one light and heavy one for each rider.
then when you pit sometime during the race, have a member of your crew swap them out. This will be a huge advantage over trying to run the heavy set-up on ice.
if you have any questions or feel i left something out, didn't explain something well enough, please feel free to contact me at: teamsnoballsNOSPAM@yahoo.com (remove the NOSPAM)
Hoffco Comet Industries may be reached at 1-800-999-8161, request their snow catalog, or visit there website using the link below.
