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Here are the rules for our 120cc classes.
Updated * 11-8-2011*
Also Minors that will be racing needs to fill out the minor release forms.
Click here for Minor release form.
Michigan Xtreme Racing 120 Program 2011/2012
120 / 4 STROKE RACING
The intent of these rules is to establish a venue in which all qualified drivers and machines can compete at their own level. These rules are definitions and guidelines for allowable modifications or alterations. If a definition, modification or alteration is not cited, then it is to be construed that no modification, alteration or change can be made to the component unless it is specifically approved by the rules committee.
Arctic Cat 120
Ski-Doo Mini Z
Polaris XCR 120
120/4 STROKE CLASSES-AGE-SPEEDLIMIT
120 STOCK 4-5 -15 mph limit 120 STOCK 6-7 18 mph limit
120 COMBINED 6-12 18 mph
120 OPEN 6-12
120 CHAMP 6-12 GENERAL SNOWMOBILE RULES
All 120/4 Stroke Classes are stock based classes. In stock based classes, no change or modification can be done to the stock qualified snowmobile unless specially allowed by these rules. If these rules do not specifically allow a change or modification, then it must be assumed that the change or modification is not allowed.
1. No traction products allowed.
2. Handlebar riser may be added. Structural integrity must be maintained.
3.Guide clips and/or track clips may be added to the track.
4. All metal ski hoops must be padded.
GENERAL COMPETITION & SAFETY
1. Driver entry into an event is open to any qualified individual. The sanctioning body has the authority to evaluate all drivers to determine their qualifications.
2. Both the owner and driver are responsible to ensure that their snowmobile and driver safety equipment conform to all of the rules for the class in which they have entered. Any driver that does not meet the requirements listed will be subject to disqualification and forfeiture of any prizes or awards, plus eligibility for the next two (2) races.
3. Teardown will be at the discretion of the 120 Tech Director.
4. If it isn’t stated in this section that it can be done, consider that it cannot be done.
5. The Race Director and/or Tech Director have the authority to determine structural integrity.
6. While driver is on the course, radio communication between driver and crew is not allowed.
MANDATORY DRIVER SAFETY EQUIPMENT
1. Snell 2005 rated helmet. Must follow the driver protective guidelines.
2. Eye Protection, either a shield or goggles.
3. Shin Guards and Knee Pads
4. Tek-Vest (Upper body protection)
5. Above ankle Boots
6. Mouth guard
STOCK CLASS RULES
1. The snowmobile must have original OEM (or factory designated replacement) engine, hood, track, frame, cowl, gas tank, carburetion, air box, suspension and clutch supplied by manufacturer for the particular model. Factory designated replacements allowed.
2. Engine RPM and vehicle speed may be monitored at the discretion of the Race Director.
3. Notice: Testing for maximum RPM limitations in stock classes will be conducted during the 2011-2012 season, the results of the testing may become applicable for 2013. This criteria may be used in lieu of engine valve spring rules in the future.
1. Unless otherwise stipulated in this section, all governor linkage must be intact, in place, and functional. Any valve spring may be used. Governor gear may be removed.
2. No component of the engine (including head, valves, and cam) may be altered, changed, or enlarged from the engine manufacturer’s original stock specifications, nor may any additional components be added to the engine.
3. Blueprinting of engines is not allowed. No removal of material whatsoever will be allowed. This is to include polishing, port matching, deburring, glass or sand blasting surfaces or material removal for the purpose of engine balancing or other reasons.
4. No changes in engine dimensions can be made by gasket adjustments.
5. Spark plugs do not have to be OEM stock.
6. No carburetor/air silencer changes allowed. Only foam maybe removed from air box.
7. Jetting changes are allowed.
8. Remote adjustable main jet system allowed.
9. The OEM exhaust system for the model must be used in its entirety. The exhaust system must be fully contained with the confines of the cowl or the chassis and direct exhaust emissions from the enclosed area. Muffler components and/or silencing material must be intact at all times.
10. In order to equalize performance between manufactures models the following changes are allowed.
a. Ski Doo racers are allowed to change valve springs to Honda P/N 14751-ZE1-000
b. Arctic Cat racers are allowed to upgrade to 120 Sno Pro kit.
c. To enhance durability, Arctic Cat racers are allowed to remove plastic governor gear.
11. Valve spring data will be added at a later date due to incomplete data. See ISOC rule book for specs.
1. Brake must be functional and operational at all times.
2. OEM drive clutch must be used with no modifications.
3. Stock drive clutch engagement must be maintained.
4. No belt drives allowed.
5. Chain guard must be in place.
6. Any gear ratio may be used in all classes.
7. Any chain tensioner may be used.
8. #35 chain and gears may be used.
SKI SUSPENSION & STEERING
1. Front suspension must be OEM stock.
2. Front suspension must remain in its stock location.
3. Ski widening devices and/or height adjustment devices are not allowed in Stock classes unless furnished as OEM and properly filed.
4. Suspension travel may be limited by means of limit straps only. Minimal suspension travel must be maintained. No rigid suspensions allowed.
5. Handlebar extensions are allowed. Maximum 3 inches each side, 4 inches down. Ends must be capped or plugged.
SKIS & RUNNERS
1. Ski must be OEM for the model and year or a commercially available aftermarket ski with a minimum overall length of 20 inches. Non sharpened carbide ski wear bars may be used.
2. Ski suspension components must be OEM.
3. Ski tips must have ski loops. Steel ski loops must be padded.
1. The complete suspension must be used as furnished and filed by the manufacturer.
2. Commercially available marginal snow wheels may be added to the slide rails. (Rear axle idler wheels must remain OEM for the model).
3. Suspension travel may be limited by means of limit straps only. Minimal suspension travel must be maintained. No rigid suspensions allowed.
4. Slide rail lubrication systems not allowed.
5. Seals may be removed from bearings.
TRACK & TRACTION
Any commercially available molded rubber track may be used. Track must fit within frame and suspension without modification to frame, suspension, or drive. Track must be used as produced by the molder. Hyfax allowed.
FRAME & BODY
1. OEM hoods only. OEM hood may be painted any color except orange.
2. Windshield may be trimmed or removed. Exposed edges of windshield must have safety bead.
3. Front and rear bumpers must be padded.
4. All sharp edges must be padded.
IGNITION & ELECTRICAL
1. An ignition tether switch must be installed and functional. Tether switch can be located anywhere except the handlebar.
2. Headlight and taillight must be OEM for model and taillight must be functional.
3. Ignition and lighting systems must be OEM for model. No modifications allowed.
4. Tachometers and/or Data acquisition systems allowed.
CHAMP 120 CLASS / 4 STROKE RULES
1. Snowmobile must be a 120/4 stroke model that complies with the General Rules and Regulations section.
2. Engine, frame, hood, must be OEM for the model.
3. Rules allowed in stock class will also be allowed in the Champ class.
1. Must start with OEM filed 120/4 stroke engine.
2. Engine components allowed for modification or change from OEM.
a. Cam shaft – maximum .290 inch lift
b. Valves and seats
i. Maximum intake valve diameter 25.2mm
ii. Maximum exhaust valve diameter 24.2mm
iii. Minimum valve stem diameter 5.5mm +-.15mm
c. Valve springs and retainers
d. Tappets and push rods
e. Governors may be removed
3. Engine overbore may not exceed .020” (.50mm) of standard bore size for the model.
4. Engine stroke must be stock as manufacturers filed specifications.
5. Engine components allowed to be modified but must begin as OEM for the engine model.
c. Connecting rod
d. Piston and Rings
f. Cylinder head
g. Crankcase and cylinder
h. Rocker arms
i. Intake manifold
j. Fan shroud
k. Carburetor insulator block may be modified, but must maintain stock thickness dimension.
6. Crankshaft journal may be turned down to allow for connecting rod bearing inserts.
7. Carburetor can be bored and modified, but must begin as OEM supplied for engine model. A velocity stack may be added to the intake side of carburetor.
8. A snowmobile type diaphragm fuel pump may be added, a pulse fitting to run pump may be added to intake tract.
9. The exhaust system may be modified or replaced. The exhaust system must be functionally silenced. Than following minimum standards for straight thru silencers are required:
a. Inner pipe must have a least 15 holes per square inch. Minimum hole size 1/16” .(minimum 3/8” sound absorbing material around the entire circumference of inner pipe.
b. Inner pipe (perforated core) must contact sound absorbing material (fiber or steel wool packing)
c. Outer pipe must be at least ¾” larger than inner pipe.
d. Minimum silencer length 3”.
e. Outer pipe must point downward and cannot protrude beyond the machine width.
11. Valve cover may be modified to stabilize rocker arm stud. Breather fitting may also be added.
Only commercially available fuel that meets the ISOC guidelines will be legal. Fuel may be mixed with petroleum, organic, vegetable, or chemical base lubricants. The use of additives which provide power boosting characteristics, are strictly forbidden. It is up to the team or driver to have their fuel tested before competing. Any driver competing with illegal fuel will be disqualified, penalized, and/or fined.
1. Ignition coil must be OEM for model.
2. Flywheel can be lightened.
3. Lighting coil may be removed.
4. Any commercially available flywheel may be used.
5. An ignition tether switch must be installed and functional. Tether switch can be located anywhere except the handlebar.
6. NO electric start systems will be allowed in Snocross racing.
1. Clutching is open. CVT type transmission allowed. Drive components must be commercially available.
2. A metal clutch / chain cover must be in place at all times during operation. It must cover clutches, gears, belts, chains, starter cups, and any other rotating components.
3. Brakes must be properly operable at all times.
4. Track drive sprockets may be modified or changed.
5. Jackshafts are allowed.
SKI SUSPENSION AND STEERING
1. Suspension must maintain OEM concept (i.e. trailing arm, “A” arm, etc.) Ski suspension and steering may be changed or modified. Materials and components must meet or exceed OEM strength and structural integrity. Must maintain suspension travel with driver seated. No rigid suspensions.
2. The structural integrity of the steering and suspension systems must be maintained.
3. Maximum ski stance is 34 inches (measured between ski runner cutter edges).
SKI AND SKI RUNNER
1. Skis may be changed to commercially available aftermarket skis.
a. Minimum length for Snocross is 20 in.
b. Ski loop must conform to GENERAL RULES AND REGULATIONS.
2. Ski runners must meet competition and safety requirements for snocross racing.
1. Track suspension may be altered, relocated or replaced. Structural integrity must be maintained.
2. Suspension must maintain a minimum of 2” of usable travel with driver seated.
3. Track and track suspension must fit and be mounted within the confines of the OEM tunnel.
TRACK AND TRACTION
1. Track must be OEM for a 120/4 stroke model from any snowmobile manufacturer.
2. Track may not be reversed.
3. No traction products allowed.
FRAME AND BODY
1. Snowmobile length must not exceed OEM for the model length by more than 2 inches (ski loop to rear of tunnel)
2. Overall body width must be within 2 inches of OEM for the model body width.
3. Bumpers must be padded (no sharp edges exposed)
4. Snow Flap must be in contact with the course surface when driver is seated.
5. Belly pan required.
6. Bulkhead may be modified or replaced; it must remain within 1 inch of the length and 1 inch of the width of the OEM bulkhead.
These regulations are comprised of definitions and allowable modification or alterations. If a definition, modification or alteration is not cited then it is to be construed that no modification, alteration or change can be made to the component unless it is specifically approved by the rules committee.
120 OPEN CLASS RULES (aka Outlaw)
1. ALL Champ 120 Class rules.
2. Motor must start out as a 205cc or less
3. Motor must not exceed 220cc after modifications
4. Must be based on 120 Chassis
5. Race Fuel is allowed
a. No Nitrous
c. No Turbo
d. No Superchargers
6. Four Stroke Only
g. No Liquid Cooled
7. Remote starters are allowed.
8. Once the race has been started, sleds requiring a remote start that stall on
the track or starting line are considered to be out of the race and will be
pulled to a safe area by track personnel.
Updates or corrections to the rule book will be made as an addendum
All 120 classes ISOC Addendum1. Rear suspension shock is allowed2. Race speeds will not be based on speed but determined by the TechnicalDirector and the race director.3. Gear change is allowed as long as the gearing is commercially available.Backer Addendum1. Not only must it be commercially available it must be preapproved by ISR andISOC’s tech director.Existing rules may be revised, or new rules may be added after this rulebook wasprinted. For the latest updates, please check the website at www.isocracing.com.
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