Clutching and gearing to slow down a sled for younger riders?

boondokr · Jun 14, 2010

I just picked up a 99 ZR440 SnoPro 136 x 2 for my 9 year old son to ride. I want to gear it down as far as possible and mess up the clutching to slow it down enough for him to live into his teenage years.
What is the lowest gear combination that will fit in the stock chaincase?
If I drop the secondary helix from the 53 degree in there now to say a 45 degree and use light tip weight in the primary can I stop the clutches from shifting all the way out without destroying belts? I want decent powder performance without being able to hit 90 mph on hardpack. I have looked for a hp or torque curve for this sled or the 97 motor in it with no luck. I think if I clutch it so that it will only turn about 7000 RPM I should be able to knock about 30 hp off and kill the top speed. Anybody have any experience or ideas?

clutch man · Jun 14, 2010

boondokr said:
I just picked up a 99 ZR440 SnoPro 136 x 2 for my 9 year old son to ride. I want to gear it down as far as possible and mess up the clutching to slow it down enough for him to live into his teenage years.
What is the lowest gear combination that will fit in the stock chaincase?
If I drop the secondary helix from the 53 degree in there now to say a 45 degree and use light tip weight in the primary can I stop the clutches from shifting all the way out without destroying belts? I want decent powder performance without being able to hit 90 mph on hardpack. I have looked for a hp or torque curve for this sled or the 97 motor in it with no luck. I think if I clutch it so that it will only turn about 7000 RPM I should be able to knock about 30 hp off and kill the top speed. Anybody have any experience or ideas?

You would need to run heaver weights and a lighter spring in the drive clutch.
I wouldn not change the driven, just the gearing to say 2.15 or 2.26 or so. that woulds slow it down to say 60 or so at 7000 rpm.

boondokr · Mar 28, 2011

Just an update for those searching later because I hate searching through unresolved threads.....
I am running 19 43 gears with a 72 pitch chain. The sled has a 4 tower comet clutch in it, so too much weight in the primary was easy. I left the secondary alone and put the softest spring I had in the primary. The carbs are always jetted at least one setting rich because kids have a bad tendency to stay in the leanest part of the midrange.
As it runs right now (after finding a dying CDI box and replacing it) the sled will pull 8000 rpms on a long flat packed trail section, but I do mean a long section. It pulls about 6000 rpms on a hard climb in heavy wet snow. The snopro doesn't have a speedometer and I forgot to put my GPS in my pocket before either of my test runs, so I don't have any speed readings.
All in all, the total package works well for a 10 yr old rider. The heavy weights give enough bog off the line to the little 440 that the sled doesn't want to trench or pull the skiis off the snow. The power curve is slow and steady, which is great for young riders. It still has enough power for me to maneuver it after he gets it stuck. It is a great little sled to learn on with plenty of room to adjust the power back in as his abilities grow.

KMMAC · Apr 20, 2011

slower down

boondokr said:
I just picked up a 99 ZR440 SnoPro 136 x 2 for my 9 year old son to ride. I want to gear it down as far as possible and mess up the clutching to slow it down enough for him to live into his teenage years.
What is the lowest gear combination that will fit in the stock chaincase?
If I drop the secondary helix from the 53 degree in there now to say a 45 degree and use light tip weight in the primary can I stop the clutches from shifting all the way out without destroying belts? I want decent powder performance without being able to hit 90 mph on hardpack. I have looked for a hp or torque curve for this sled or the 97 motor in it with no luck. I think if I clutch it so that it will only turn about 7000 RPM I should be able to knock about 30 hp off and kill the top speed. Anybody have any experience or ideas?

I would look into some sort of throttle block. One thing I would be concerned with as far as gearing down or changing up the clutching is it will cause the engine to over rev and who knows what will happen to the belt. This might seem like a task but in the long run will make it easier to set up after he learns how to handle the power..

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Clutching and gearing to slow down a sled for younger riders?

boondokr

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clutch man

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boondokr

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KMMAC

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