How gearing affects clutching and rpm by MrViper700

Allot of times someone will get a clutch set up as a suggestion and it does not work the same or perform quite how it was described. There’s something else that affects your clutching, it’s your chain case gearing. By the amount of ratio you run in your chain case has a direct result in the amount of clutch weight the engine will be able to effectively pull to rpm.

Lets say you’re running a steeper gear set up(larger numerically) for tight woods riding, short blast across hay fields to get to another section of "trails" thru the woods, running a smaller top gear is what most will do. This does accomplish the task but it also has a few down falls if taken too far (too small of a sprocket). Anytime you bend the chain in the chain case tighter around a smaller sprocket you require more power to turn the chain around the tight radius. This is the same exact thing as a larger rear idler wheel for the track or even the same as running the belt in a better ratio in the clutch's, a tighter radius takes more power to turn the object in a tighter radius. Also something to watch for is the bend you’ll get in the chain when using a small top sprocket with less teeth and the stock chain length, the more bend you apply to the chain via the chain tensioner to get the slack out of the chain is also eating up power.


Back to gearing ratios for the type of riding you do 90 % of the time. By gearing lower, you first are taking load OFF of the engine by doing this, it multiplies torque, when you gear down, but too much can be a step backwards as mentioned before. What you need to do is find a ratio that satisfies’s your speed requirements for the distance and type of terrain you encounter the most.

Most all stock sleds will be geared higher (lower numerically) then the mph they can obtain, the reason for this is too simply keep the belt speeds down. A higher belt speed is dangerous and leads to blown belts. The other plus of gearing tall is the free power you get by making the clutches more efficient, they grab more of the belt and bend it in a larger radius requiring less power to turn the belt thru the radius in the primary and secondary clutches. Taller gearing also LOADS the motor more, there are some engines like the srx700 that just loves to be loaded hard and let it tractor its way up to peak hp rpm. So gearing taller actually is an advantage with that particular engines personality.
The exact opposite can be true for a peaky higher strung engine, a peaky engine will need the gearing to be steep to keep the engine on its peak, by falling off then peak the engine may lose a ton of power, this was very much true for the older srx440's, get off the power curve and the race was over, very narrow power band, allot easier to run/clutch with a deeper gear in the sled.

So knowing we are taking the load off the engine the engine by gearing lower, the engine will now easily pull MORE clutch weight to maintain the same rpm as before, so this is where someone may suggest you run the clutch weights at say example: "60 grams per arm" or whatever and they didn’t work in your sled (wrong rpm), you might need to change the gearing to match the other persons gearing if you can’t seem to make the set up run correct rpm. If the gearing of the other person and the gearing you wish to run are 2 different to compromise then you’ll need to adjust the flyweights to run the correct rpm, by either removing weight or adding it.

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