Micro Sprint Rules

Marion County Speedway/ “The Bullring”

Jan 18,2019

These are the rules for the SUNSHINE MICROSPRINTS

1) Driver age; driver shall be at least 12 yrs old with no maximum age limit. Drivers who are under the age of 12 but with karting experience please contact the group. All drivers running the East Bay races has to be atleast 14 yrs old at the beginning of the season.
2) CARS; chassis must be of the microsprint design( 250 or 600 ) no up right or lightning sprint chassis.
3) WINGS ; Wings are allowed with a maximum of 12sq feet and 54″ side boards. Wicker bills are allowed.
4)TIRES: tires are open in sizes and compounds.
5)Fuel: Pump gas or Race fuel. NO METHANOL. Do to the on going us of ethanol in the use of pump gas as a standard. We are going to allow up to a 15% content in the fuel. Random fuel samples may be taken thru out the season to check for content.
6) ENGINE: Will be either ATV or Dirt Bike in origin. Any manufacture. No road race engines allowed.
7) These rules apply to all cars weighing 610 lbs and under 750 lbs. with a minimum weight of 610lbs
A) All engines will be completely stock and unmodified except as specified in the rules. IF IT DOESN’T SAY YOU CAN DO IT THEN YOU CAN’T.
B) No multi cylinder engines
c) Any year or manufacture is allowed.
d) PISTON- 250(2stroke )MOD may run a larger bore piston from stock with a max displacement of 265 cc’s . 450 (4stroke) must run a stock bore size with a 450cc max. Any piston manufacture is allowed
e) Crankshafts; THERE WILL BE NO STROKERS ALLOWED. MUST BE OEM SPEC FOR THE BRAND AND MODEL OF YOUR ENGINE ( BRANDS ALLOWED; Wiseco , Hot Rods or OEM stock cranks) Crankshaft must be steel , no light weight or knife edged rods, no titanium or light weight materials allowed unless used by the factory for balancing. no machining or modifications allowed. any OEM spec specific rod for the year and brand of your engine can be used for rebuilding of the crank.
f) HEADS; 250 MOD can run either a stock head or a cool head design. 450’s must remain stock with stock oem spec valve sizes. After market valves can be run. Heads may be surfaced for flatness and a valve job for refreshing is allowed. No porting of the head.. 
g) 450 4strokes may run a stage 1 Hot Cam or stock cams. No other manufacture or cam is allowed.
h) 250 Mod’s may run a ported cylinder. the cylinder may be rebuilt with either a sleeve or replating.
j) CLUTCH; 250 mod’s may run a machined or welded clutch. 450’s must have a operating clutch ( to encourage elect start)
k) Oil systems can be modified for durability. No dry sump engines unless it came from the factory.
M) MUFFLERS; Any muffler combination is allowed
8) This is for cars weighing over 750lbs these rules will apply
1) 2 Strokes . Engine can be of any manufacture with a bore and stroke combination not to exceed 270cc. All other 2 stroke rules apply
2) 4 stroke engines may have a max displacement of 545 cc’s max bore size cylinder. NO STROKER CRANKS ALLOWED. May run either stock manufacture, stage 1 Hot Cam or a stage 2 Hot Cam. No other manufacture or cam allowed. All other 4 stroke rules still apply



  • MCS always welcomes any and all other race classes and sanctioning bodies.
  • MCS will run a Micro Sprint Limited Class as well. Please see MCS Limited Micro Sprint Rules Package.
  • MCS will establish a rules package for a 270 Micro Sprint class. If there are any 270 Micro Sprints wanting to establish a series, Please contact us for class structure.


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