Gearing - Mountain Specific
Gearing - Summit 800etec over revving on road
Gearing - Change track from 1.25 to 1.75


Gearing - Mountain Specific

If you ever want to regear, it’s not a problem with this kit to go any of these ratios, in fact my helix’s work so well with lower gearing for whatever track speed you achieve, it will maintain it with great strength.  Lower gear; even stronger track speed holding power.

XP/XM Chassis
21:49 = 2.33 = 104P
19:45 = 2.36 = 102P
21:51 = 2.42 = 106P
20:49 = 2.45 = 104P
20:51 = 2.55 = 106P  
19:49 = 2.57 = 104P
19:51 = 2.68 = 106P

Rev chassis
19:45 = 2.36
19:46 = 2.42
19:47 = 2.47
19:50 = 2.63
19:51 = 2.68


Gearing - Summit 800etec over revving on road

Larry writes) I am running 21.5 grams of weight, on clicker 3, stock gearing, 20XX 800etec 154" summit.  
Testing was done on hardpack trail, initial rpm's WOT 7900, held the wot and started climbing in rpms after a period of time, until hitting the rev limiter.  1200 feet altitude, I was not able to get top speed reading.  

A couple of questions: 
1] Normal operation is not trail use, so I would not hold it WOT like I did for testing.  It took quite a while for rpms to start increasing under WOT.    All short WOT operation, small hills, midwest riding in UP of Michigan.  
2] Should I be testing in off trail conditions?

Moe writes) Hardpack is fine for going for a ride to see if there are any bugs or anything was installed incorrectly or needs to be adjusted.

The clutching is designed for getting more track speed in deep snow when breaking fresh snow and enhancing the backshift strength.  Breaking fresh snow, backshift much stronger and able to maintain full throttle in deep snow and have correct engine speed for long periods of time.  Continuous cycling of throttle with strong recovery.


Your sled is geared @ 19:49 so lets find out how fast the theoretical vehicle speed will be.

Far as going out on hardpack you’ll end up finding out what top end is real quick and when the clutches shift out the engine takes off into overrev.


Sledders talk about overreving their lower geared sleds....
Questions to ask) When you hit the throttle from a dead stop, does the engine go to 84~8500 right away (yes or no)
IF no, then what engine speed does the tach go to when you punch the throttle?

When you are traveling along part throttle at 30~40mph and hit the throttle full, does the engine go to 84~8500 right away (yes or no)
IF no, then what engine speed does the tach go to when you punch the throttle?

What vehicle speed does the engine start to go past its rated engine speed?
Comment – what we are looking for is “When does the engine overrev?”
Right away in 10 feet or like 400 feet or more?

Next question - Is there any speed from 0kmh to 60mph that is less than 8500? Yes or no?
To prove the clutch shifted out and cannot stroke anymore - Go prove this yourself - Take a felt marker and mark the primary clutch.


Now go take your full throttle run and watch the tachometer.  7900~8000~7900....and then eventually it starts to go over 8000 – STOP!
Pop the side panel and look where the felt marker was wiped off and now you have proof that you are expecting more out of your gear ratio than what your sled has for maximum speed.

Once the clutch achieves overdrive and stops stroking then...Adding flyweight is not going to stop overrevving from 8000 to 8500.  Lowering the clicker is not going to stop overrevving from 8000 to 8500.

The only way you will stop the overrev at the speed its been overrevving is to....

  • Gear up.  1 tooth will increase about 3.5mph theoretical top end.
  • Put the sled on the back of a truck
  • Falling off a cliff.  haha

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Gearing - Change track from 1.25 to 1.75

Question) Hi I was wondering if it would be better to go down two top gear teeth when taking out my 1.25” track and putting in a 1.75 on a xp 600 carburetor.  Does the little 600 carb have enough power without breaking belts to turn the 1.75 when you get into deeper snow?

I don't want to lose all the top end speed but I love playing in powder. When I ride with my father it's 80mph all-day and don't want to be W.O.T. all-day.

Answer) For every 1/4" increase of track lug height you could be gearing down at least 1 tooth on an 800.  On a 600 you can go 2 teeth down for every 1/4" of lug height increase.

2010 600 Carb gearing should be 25:45 with original 1.25 track.

The latest 600 Rene' BCX's geared at 21:49 (equivalent gear to 19:45 gears)

Going to the 120x1.75 track, I would at least run a 21 top gear with a 104P chain.


This is an important question(s) for any tuner - its right at the top of questions when changing a track lug size.
Question on top speed – what is the highest most reasonable peak vehicle speed you want to achieve with the new "X" size lug track?  Be sensible about the peak speed. 

Question - time at top speed - How much time do you spend at your highest vehicle speed chosen?  (When I say high, I mean from 3/4 speed to full speed of this potential vehicle speed you are being sensible about)  Is the time several seconds?  Just a quick shot to top end?  Several seconds?  30 or more?

Keep in mind the engine power you have.  A carburetor 600 is about 104~106hp and want to push a 1.75 track to 90+mph on GPS or Radar?  Going that fast is going to be difficult to uphold.  I'm not talking speedometer, rather talking GPS speed measurement.

There are 2 significant clutch ratio lines inside the clutches.  First is 1:1 clutch ratio.  The engine speed is the same as secondary shaft speed.  1:1 clutch ratio is roughly 3/4 of an inch from the rim of the primary.  Second is the outer rim of the primary.  From ¾ of an inch to the rim of the primary clutch, that is where the secondary shaft speed continuously increases speed over engine speed.  The secondary shaft can turn up to 17% faster than the engine. (Difficult to tune in this range)


The orange boxes show where the drive belt would be in the middle of the overdrive portion.  Those figures reveal where the drive belt is about 7/16 from the rim of the primary clutch.  To achieve top speed and uphold it, some conditions need to be met.  Good conditions are; correct snow lubrication, not deep snow, soft suspension settings, flat ground, not much wind, good fuel octane, good engine and clutch fitness.  With conditions met, one can achieve speed values in the orange boxes (middle of o.d.)


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