Series Rules

 

The Midwest Champions Series will be using IKF rules for race management and flathead engine rules. Please note the new rules for clones effective for Race #4 Shirtworks Shootout at Newton.


  1. BulletClone - any color, big pipe, billet flywheel, drum clutch - medium and heavy

  2. BulletRookie Box Stock Project .425 Silver Restrictor Plate to run with Rookies



All Box Stock engines must use ARC Part number 6619 ARC, which is an SFI certified flywheel. No adjustable flywheels. Stock timing




Box Stock Project (see detailed rules below)


  1. Approved engine: Clone 6.5 OHV only - any color

  2. Stamped Steel drum shoe type clutch

  3. 87 octane gas

  4. Claim - $300 (engine only, lead lap kart out of the top 5 can claim winner, 1 claim per race, first to claim to tech man)



Box Stock Project Rookie


  1. Approved engine: Clone 6.5 OHV only

  2. Any clutch

  3. .425 Silver Restrictor Plate

  4. .750” header with BS tube muffler #89966

  5. 87 octane gas

  6. No Claim

  7. Will run with the Rookie class with flatheads



Box Stock Rules



BOX STOCK SENIOR Age 15 years & up – 375 lbs. – 87 Octane Gas Only

BOX STOCK Rookie  Age 5-8 – 225 lbs. – .425 Silver Restrictor Plate - 87 Octane Gas Only


Approved engine: Any color clone 6.5 OHV


Stamped steel drum shoe type clutches only.


Description: Single cylinder, 2 valve, OHV 4 cycle



All Engine parts must be stock OEM parts unless otherwise spelled out. All gaskets must conform to stock configuration. Using more than one gasket for side cover clearance is acceptable.  Allow plus or minus .005”  tolerance on all measurements.


Fuel will be gasoline. 87-93 octane maximum. No aftermarket coatings of any type are permitted on any part of the engine.


Fuel tank must be removed from engine for safety reasons.


Floor mounted fuel tank can be pulsed from crankcase or valve cover. Any pulse type fuel pump permitted.


Carburetor: Huayi or Rui*ing allowed.  All stock carb gaskets must be present. One extra gasket must be used with restrictor plates.  Choke assembly must be functional. Choke bore must be cast.  Venturi .615” No-Go. Back carb bore .751” No-Go. Emulsion tube (E-tube) must remain stock .064” No-Go.  Main jet  Non-Tech. Low Speed idle jet .019” No-Go.


After market air filter adaptor is OK for use (with K&N style filter) maximum length: 1.375.


Block must remain stock. Maximum bore is 2.685”. Stroke is 2.123” plus or minus .005”.

Governor and governor components are non-tech.

Use of multiple gaskets is okay (gaskets must be stock configuration).


Combustion chamber minimum: 26.5cc with piston at TDC. To be measured using prescribed technique.

Block may be welded for repairs as long as the repair does not constitute a functional modification to the block.   No welding to block above cooling fins.


Cylinder Head:  No porting, grinding or modification. Valve seats have two angles: single 45° bottom and single 30° top. Head gasket must be stock configuration.

Valve train will remain stock. No polishing. No grinding. No Alterations. Stock 1:1 ratio OEM rocker arms only. Stock valve springs only. Maximum spring wire diameter is .0705”. Maximum spring pressure is 10.8 lbs. at an installed height of .850”.

Stock rod only; no modifications. Stock crankshaft only; no modifications.

Stock piston only. Stock rings only.


Camshaft: Maximum running lift on exhaust is .242” taken on valve spring retainer with zero lash. Maximum running lift on intake is .238” taken on valve spring retainer with zero lash.  Camshaft base circle measurement:   .865” - .005 “+ .010”.  Duration check for Intake and Exhaust lobes.  Intake duration of 218.5 degrees at .050 lift/85.5 degrees at .200 lift.  Exhaust duration of 221.5 degrees at .050 lift/96.5 degrees at .200 lift.  (All checks will allow +2 degrees for wear and gauge variances.)


Flywheel and ignition coil must be stock. NO alterations, NO machining. Timing must be stock with stock flywheel key. Plastic fins must remain stock. Only approved flywheel is ARC 6619, fixed timing billet flywheel.


Header and Muffler:  Multi stage header is okay.  Maximum length is 22”.   Header may be bent in any configuration to keep it away from the driver and the muffler will not extend past the rear bumper. The RLV B-91 muffler/silencer is mandatory and may not be modified in any way.  Header must be securely wrapped from flange to muffler prior to the race.  No loop headers.


Pull starter must be present and remain stock. You may rotate pull starter for a better angle to crank from.

Engine oil recovery system mandatory (oil catch can).


The above rules are written with the idea of simple tech in justifying the winner and runners up. Do Not Read Into The Rules What Is Not There!  


Claimer Rule: You must finish the race in the box stock class to purchase the winners engine for $300 (minus the clutch/chain guard/throttle kit, header pipe/muffler, air filter adaptor/air filter, top plate & fuel pump).



No other alterations to or from stock components are allowed.

Rainout policy: o Rainouts after heats are run but not a class feature– payout by feature lineup for features not completed o Heats that don’t complete, not allowing the feature lineups to be created – refund of $25 of the $30 entry fees of those classes to affected racers if a delay to race later is not possible. $5 per entry pays for race management on site. o A feature that begins and doesn’t complete will pay based on line up if less than half the race is run or by running current order if more than half the race is run. o If an entire single day is rained out that day’s events will not be rescheduled. o In the event that the entire event is rained out, the entire event may be canceled and possibly rescheduled. o All efforts will be made to run at least one full race program on the originally scheduled race weekend. o Pit pass fees will not be refunded under any circumstances. Midwest Champions Series 2009 Rules.pdf