You want to run your track as loose as you can without the drivers slipping on the cogs. For maximum performance loosen your track until the drivers slip when your rider is sitting on the machine, then tighten up the track just enough to keep the drivers from slipping.
These sleds have a very small track. This makes the track hard to bend. When you try to bend the track at a sharp angle is where you are losing horsepower. The path of least resistance for the track would be a perfect circle (as seen from the side). We know this would be impossible and defeats the purpose of a snowmobile, but this does help to explain that the rounder or more oval shaped you can keep your track the less horse power you will scrub and the faster your 120 will be. This is accomplished by tightening up the limiter straps in your rear skid frame. The tighter you can get them the less track angle you will have. In some cases you will have to drill new holes in your straps to allow you to shorten the straps. This will decrease your suspension travel, but it will gain you top speed. Please refer to the illustrations below.
These machines are not designed to accept different gear combinations. With certain gear combos it is impossible to tighten the chain to factory specifications. This is more noticeable on the Polaris. You may be forced to run the chain looser than you would
like. This is not a problem, it is actually faster to run the chain looser. In certain situations with the Polaris your chain may be so loose that it will rub on the muffler bracket when you move the machine around by hand. When the machine is under its own power the front gear pulls from the top tensioning the chain, not allowing it to hit the bracket any longer.
By placing a mark on the upper half of your spark plug on the same side as the gap is on the lower half, you will be able to align your gap with the intake charge after the plug is installed. If your plug doesn’t line up with the intake side of your motor you can adjust with different size washers of a plug indexing kit from your local speed shop. This will keep the gap and the meat of the spark in direct contact with the intake charge.
Run the 2001 drivers on your 2000 Arctic Cat Z120. This will reduce track friction and increase top speed.
We have found two things that cause heat in your 120 clutch.
1. The first thing you are going to want to check is your brake band. If your brake band is too tight it will cause friction and heat. To check if your band is hanging up start your machine and run the track wide open for 30 seconds. Without using the brakes allow the 120 to idle down then turn off the engine. Feel the brake band, if it is hot to the touch it is hanging up and needs to be adjusted.
2. Clutch shoe slippage. This is caused by too high of spring tension for the amount of weight you have in the clutch. This is commonly verified by a chattering sound and a jerky feel at engagement. To cure this you need to add weight to the clutch or reduce the spring tension. Dirty weights can also cause slippage. This can be fixed by removing the shoes and cleaning them with a carb cleaning spray and drying them with an air gun. To take it a step further you can take a rat tail file and cut two small groves across the surface of the weight, parallel with the crank shaft. This will give the dust a place to go and allow the rest of your weight to contact your clutch.
The track driver alignment can be off. The only way to resolve this problem is to remove them and grind to fit. This will void your warranty. The rear gear to clutch gear alignment can be off. This is easily corrected by adding or subtracting washers behind the rear gear until it is properly aligned with the clutch gear. The Arctic Cat Z120 has another friction problem you might want to watch out for. There are not track clips on every window and may cause excess friction during marginal snow conditions.
Testing has shown that plastic skis will add a little over 1mph. If you have a Polaris your set because it comes stock with plastic skis.
Energy Release additive in the oil will help, especially a heat soaked engine that has been running at max rpm for an extended period of time.
Q I just put smaller gearing on my 120 and it has less performance or will not move at all what is wrong?
A This could be one or more of many things. First place to check is your brake band, make sure it is not hanging up. Next make sure you have a governor bypass kit installed, this is a must with smaller gearing. Check to make sure you have enough weight in your clutch for your set up. Make sure your track is not too tight or binding, (note your sled will be slower without a rear wheel kit). Check to see that your drive chain is not out of alignment or binding. Do not run higher than 87-octane fuel. Make sure your kids do the testing; these 120s were not designed to haul around adults.
Q What type of fuel should I be running?
A Octane is an anti-knock rating. This rating depends on how many additives have been added to the fuel. The higher the Octane the longer the molecule chains and the cooler and slower they burn. A stock 120 will actually run faster on a lower octane fuel. The only reason you should have to run a high-octane fuel would be if you have had motor work done or are running a high compression head.
Q I have an Arctic Cat Z120. The Holeshot hub has a round key way and my sled has a square key, did I receive the wrong hub?
A No, The hub was designed that way. Your key will fit; if it doesn’t all you have to do is touch the top two corners on you key with a file and the key will fit and work with no problem.
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