November 25, 2007

Performance Is Where You Find It



Cutler offers tips to find more

Have you ever wondered why your friend’s snowmobile is faster than yours?

Both snowmobiles are the same make, model, size and both have approximately the same number of miles. At our research and development department we have found this very phenomenon to be true. We can uncrate two brand new snowmobiles of the same model and size and one of them will be a little faster. Even though they are set up exactly the same, the fact exists that they are two different snowmobiles made out of different parts with individual identities and personalities.

Performance is where you find it. To unlock this mystery and for ease of discussion, lets examine six categories where hidden performance lies. They include engine, carburetion, clutching, gearing, drive train and chassis.

Engine

The engine is the primary source of power. If one engine is more efficient than another engine then it will out perform the other. Several areas need to be checked. One of the easiest and least expensive is to verify ignition timing. The most accurate way to check timing will require several specialized tools including a timing light, battery and dial indicator. Some manufacturers check ignition timing hot, others with a cold engine. Make sure that you check the timing according to the shop manuals. Most manufactures will specify an exact rpm at which the timing is to be checked. If the timing is not correct, you will need to make changes to improve you performance.

Remove the spark plugs and check them. This is also an excellent time to check compression. Screw on a compression gauge and turn the engine over several times. Compare compression reading with the shop manual. If low compression exists, you will never perform at peak performance until the problem is repaired. Most low compression problems are the result of scored cylinders or worn pistons/cylinders from high mileage. Scored cylinders are due to improper air/fuel mixture or mechanical failure. In any case your local snowmobile dealer will be able to help you solve and repair the problem. Another area of lost performance could be a cracked exhaust pipe or leaky ball joint. Worn exhaust systems may need to be replaced.

The use of RTV high temperature silicone can be used to seal the leaky joints. New exhaust springs will also help. A leaking exhaust system will mean lower performance due to a loss of intensity in the pressure waves in the exhaust pipe, which affects the scavenging of the fuel (the management of fuel being drawn into the combustion chamber by way of the transfer ports).

Carburetion

A correct carburetion calibration is essential for snowmobile engines to run correctly. Before you make any clutch changes, it is essential to make sure that the carburetor is clean and free from any varnish build up.

If the snowmobile has been sitting for four months or longer with fuel in it, we recommend that the carburetors be removed, disassembled and soaked in carburetor cleaner. Each part should be washed off, then dried with compressed air. Check each component (main jet, pilot jet, needle jet, etc.) to see if the jets are correct for your altitude and riding temperature. The floats must also be set at the correct height. Also, the needle and seat should be checked by performing a “leak down a test” to insure that it holds pressure. Your snowmobile dealer will need to perform this test because it will require a special tool. If your snowmobile has dual carburetors, they must be synchronized. Choke cables should also be checked to make sure they are working properly. Your air box should be clean and free from any dirt of belt fiber.

Clutches

Both the drive clutch and the driven clutch should be checked and inspected for wear. Trying to calibrate a worn out clutch is frustrating as well as a waste of time. Belt fiber and dirt must be cleaned with compressed air. The clutches should be lubed with a heavy duty silicone dry lube. Silicone will not build up or attract dirt or belt fiber like petroleum-based lubricants. If any components within the clutches are worn, they must be replaced. Special areas of attention should include examination of the rollers on the spider and the bushings in the cam arms in the drive clutch. Also the helix wear pads within the driven clutch should be checked and/or replaced. If the helix in the driven clutch is scratched from wear and tear, then they can be polished in the contact area where the wear buttons slide with some 320 emery cloth. If your driven clutch has rollers, then they should be inspected for wear, especially in the axle area where the rollers pivot.

Gearing

The most important component on the drive system is the belt. A worn or stretched belt will destroy your performance. If in doubt, temporarily install a new belt to see if your performance improves. Center to center distance must be correct and clutch off set must be checked.

Within the chaincase of each snowmobile there is a set of gears. Each season the chaincase cover should be removed. This allows the chain and gears to be inspected. The oil should be drained out, the chain and gears should be removed and inspected. The chain must be free of any kinks and should not exhibit wear or broken links. Also, the gears should not have any clipped teeth or noticeable wear on the teeth. If premature wear is found, they should be replaced. While the gears are out of the chaincase you should count the number of teeth on each gear and compare the ratio with your snowmobile manufacturer’s recommendations. Most high altitude setups include lower gear ratios. A lower gear ratio allows your snowmobile to perform better due to the horsepower robbing effect that is encountered at altitude. Lower gear ratios also improve belt life in extremely deep powder conditions.

Drive Train

Power is transferred from the engine to the drive clutch, from the drive clutch to the driven clutch then through the chaincase to the drive shaft. The drive shaft turns the track. The track rides on a combination of idler wheels and hifax. The point I am making is that as power is transferred through each shaft and as each wheel or gear turns, it pivots on a bearing.

These bearings are exposed to snow and the elements. Sooner or later the bearings get rough and fail. Power is robbed by each bearing that is marginal or that has failed. Each snow season the rear suspension should be removed and each bearing and idler wheel should be checked and replaced as needed.

Hifax should also be checked and replaced as needed. Another power robbing factor could be a track that is out of adjustment. If the track pulls to one side or the other, it will take more power to spin the track. Also a track that is over tightened will rob power as well.

With the ACT Drive system Arctic Cat now uses in many of its snowmobiles, that means some special attention needs to be paid to sleds with that drive system. You should change the drive case oil every 500 miles if you ride in deep powder or are an extreme mountain rider. If you mostly ride trails, then changing the oil every 1,000 will suffice.

Chassis

The last area to discuss is the chassis. Adjustments can be made to the front suspension for a correct toe in and toe out measurements. All front end alignments should be adjusted to have about one fourth of an inch toe out (meaning the front ski tips are wider than the back). This will keep the snowmobile from darting. Toe in steering will rob power just as a downhill skier will put his ski tips together (snow plowing) to slow down.

The position of your track in relation to the rear suspension will give you more or less ski pressure. Dropping the front of your skid frame down will give you less ski pressure and more traction for climbing hills or going through deep powder. In reverse, if you suck your front part of the rear suspension up into your tunnel, your track will be more oval shape and take less horsepower to spin the track.

This set up may work well for speed runs. The point is that there are many ways to set up your snowmobile’s suspension. Adjustments are available for you to fine tune your snowmobile and meet your specific riding style. Performance is where you find it.

 

(ED—Cutler owns Cutler’s Performance Center in Orem, UT. This is an excerpt from his book, Clutch Tuning Handbook, which offers lots of information on how to keep your snowmobile running at its best for peak performance. For a copy of the book, contact Cutler’s at 801-224-5005. The book retails for $19.95 and has 106 pages with more than 100 photos. For more information on Cutler’s, log on to www.cpcracing.com.)








Ice Age Performance
Bear Lake CVB


Search SnoWest
| Promotional Offers | Contact Us | Subscription Service | Advertise | Media Kit | Picture of the Week | Content Archive |
© 2014 SnoWest® Magazine Published by Harris Publishing, Inc.