|2023 MINI CUP
Auburndale Mini Cup Rules
|Driver and Team Conduct
Assumption of Risk
Payout / Trophies
Mini Cup Racing Safety Equipment
|Radios & Race Receiver
|Head and Neck Restraint
GEAR RULE 4.29
Minicup Engine Rules 2022
Engine Platforms Permitted: GX 390 Honda * For Sealed Class
*With the exception of some internal parts.
GX 390 Honda or Clone Block for MODIFIED
Sealed Class Rules:
This class is intended to be easy to tech at the track and is designed to keep a level playing field. With that in mind, APPROVED engine builders are empowered to seal engines and keep record of the seals and engine numbers, to help expedite tech and assure quality racing! The approved engine builders of CFMC are:
VP Racing Engines PH:352-262-4901 email@example.com
Big Cheese Racing Engines PH:863-860-2934 Bigcheeseracing3@aol.com
Seals may not be removed, nor serial numbers or stamped numbers be removed from block!
Engine must remain in stock location. Offsetting of engine is expressly prohibited
Detailed Engine Rules:
Due to a shortage of some parts, the following may differ from rules of the past! The changes have been put into place in an effort to increase participation and to overcome some difficulties in obtaining replacement parts for rebuilds.
All GX 390 stock blocks are legal. Non electric start blocks may be prepped for an electric starter. Block must have no more than .005” piston pop up. Block may be repaired by use of welding, epoxy, or both due to failure of internal parts. Block may be sleeved. Lifter liners may be installed into block and relived.
The governor must be removed, and holes can be plugged or vented.
The oil alert system may be removed, and hole may be plugged.
All Honda Factory heads allowed. Large AND Small port heads ARE legal.
Any Dished Honda piston allowed. Must meet specs on detail sheet. Piston may be machined to meet spec.
Rings non tech except NO gapless rings.
May be bored oversize to a maximum of .030 + clearance and wear.
Crankshaft may be shortened a maximum of 1.250” and hole may be re-tapped. Crankshaft lobes may not me machined or polished. Crankshaft may be reground .010 under size and appropriate rod journal bearing may be used.
ARC 6272 Rod may be used with insert bearing. Minimum weight on detail sheet.
Honda rod may also be used with any bolts.
Must use stock style wrist pin and clips. May be lightened to meet spec on detail sheet.
Camshaft must be Honda or clone solid core design. A reground camshaft must meet the following criteria: Intake= .265” lift max , Duration at .050”= 260 Degrees
Exhaust= .265” lift max, Duration at .050” = 260 Degrees
All measurements taken at the lifter. Camshaft must line up on factory timing marks. Machining of face of camshaft to remove weight allowed to meet spec.
Must use factory balance shaft.
Bearings non tech except cannot be self-aligning.
Cylinder Head: No porting of cylinder head allowed. May be machined to spec thickness of 3.725”.
Three angle valve job allowed.
Valve seat must remain stock other than surfacing seat.
Valve guides may be replaced with factory dimensioned guides or liners may be installed.
Stock Honda valves must be used. With or without rotator. Must meet specs on detail sheet.
Valve springs must be single coil.
Retainers must be stock.
Valve shims may be used. Valve seal may be used on intake valve.
Honda rockers (GX390 Stamped steel) must be used. Rocker arm may have hole elongated to prevent binding. Rocker contact patch may be ground to achieve proper geometry. Honda rocker stud, pivot, and nut must be used, and in stock condition.
Stock pushrods of stock length must be used. See specs on detail sheet.
Stock pushrod guide plate must be used.
Stock Lifters must be used. May be machined to meet spec. Liners may be installed in lifter bores. Bores may be chamfer relived.
Flywheel must be stock Honda. Minimum weight is 11 pounds 10 oz. Weight must be removed from the outside perimeter of flywheel only. Evidence of machining elsewhere on flywheel is grounds for disqualification. Magnets may be removed. Charging system must be removed.
Stock flywheel fan, nut, and retaining washer must be used.
Stock Honda or clone ignition coil must be used.
Spark plug boot may be of any style except spark intensifier!
Any Spark plug allowed.
Starter must be in working order.
Starter cup and rotating screen must be removed and replaced with a protective Cover. This cover may be of ¼” mesh, solid metal, or solid plastic, WITH HOLES. Holes may be no larger than ½” to retain a level of safety. Cover may be taped or covered to obtain engine temperatures desired. Must be fastened securely to the blower housing. A hole may be cut in center of mesh to allow the use of an external electric starter.
Stock Blower housing mandatory.
Sheet metal over cylinder is optional.
All gaskets must be Honda style. All gaskets must be present.
All bolts are non tech besides Head bolts. Head bolts must remain stock.
Studs may be used anywhere besides the Head bolts.
Valve cover must remain stock. Vent may be modified to accept a durable connection to prevent leakage onto track. Must be connected to a catch device of some type.
Exhaust pipe non tech, except must be securely mounted and safety wired, and cannot be adjustable under way. Brace recommended but not mandatory.
Honda Kehin cast carb body. Venturi bore max no-go .960”. Epoxy allowed. No other tech requirements besides Cannot be a pressurized closed loop Fuel System. Adjustable high-speed needle allowed.
Tillotson HL360A: Stock venturi and bore. Venturi .945” and bore 1.060”. Use with manifold and velocity stack. Fuel pump must be pulsed from intake manifold. No other technical inspection. Cannot be a pressurized closed loop fuel system. Any manifold allowed.
Mini cup Sealed Stock Engine Parts Detail
The intent of the following list of measurements is to make clear what is a legal “stock” part. This is a logical approach to truly leveling the playing field. All Measurements must be within tolerance stated and measured to the level of precision as stated. As a rule, there is no rounding up or down of any measurements. Actual measurements as to comply with a GO/NO-GO mentality will be followed as grounds for disqualification. All Measurement tools and GO/NO-GO gages have been calibrated and can be checked at the location of inspection. The following parts, as listed in detail, must meet the following criteria to be deemed legal. Parts may be machined to meet the stated values but may not surpass the boundaries of the rules.
Parts to be measured in .001 thousandths of an inch, or to be measured to (0.1) Gram resolution:
|Name of part:||Min Weight if applicable:||Minimum Size:||Maximum Size:||Special***|
|All Pistons||Min 250 Grams||NA||Approx .030”Oversize||Machining Allowed|
|Piston Dome Shape||Top of Piston must have at minimum a .060” Depression Measurable in 3 places||Must remain similar in shape to factory dish||Must have radius of minimum .0625” /Maximum .25”, on transition||Raised section to have radial section width less than .380”|
|Rings||Any ring besides gapless allowed||Non tech||Lapping and gapping allowed||Must use factory style oil rings (3 piece)|
|Wrist Pin||70 Grams||Factory O.D. .787” +/- .003”||Machining allowed|
|Circlips||2 must be used||Non tech||Non tech||Non tech|
|265 Grams||Must remain as produced besides clearancing||Bearing/ Bolts, non tech||Truing and providing side clearance allowed|
|Crankshaft||Honda Only! Must remain as prepared from the factory. Broken Key Damage may be repaired.
Hole in end may be re tapped.
|May not remove more than 1.250” from end||Clearance for bearings and regrinding of up to .010” undersize permissible||Stock Stroke only !!|
|Cam||675 Grams , INT & EXH: .265” Max lift at lifter, Max Duration at .050: lift INT & EXH: .260”
|Cam gear may be lightened to meet spec||Compression release must be in place||Machining allowed|
|Lifters||26 Grams||May be straightened and trued to spec||Must compare to Factory design||Machining allowed|
|Pushrods||22 Grams||May be straightened and trued to spec||Must compare to factory design||Machining allowed|
|Rockers||20 Grams||Standard Honda Rocker ratio and length||May be ground to spec on weight||Machining allowed|
|Rocker nut/stud/ and jam nut||Must be Honda Stock||NA||NA||NA|
|Retainers and rotator||9 Grams
Honda Style ( no 2 piece keepers)
|Rotator is optional||Stock dimensions||Machining allowed|
Must be Honda Stock
Stock 45 Degree Only!
|1.230” Int Max
1.390” Exh Max
|Length Non tech||Machining allowed
No Knife edging!
|Valve Seats||Three angle Valve seats permitted. I.D. of seat must remain stock||NA||NA||NA|
|Valve Springs||Any Single coil springs and shims allowed||No rules on springs
|Only visual for single coil design||Machining Allowed|
|Flywheel||11lbs. 10 Oz minimum
Stock Honda Only
Puller holes may be enlarged and retaped for flywheel removal
|Must be machined on outside perimeter only!||Balancing also allowed||Machining allowed|
|Fan and cup and Nut||Must use factory flywheel fan||Any flywheel retention nut allowed||Fan retention cup may be trimmed down||Moving screen must be removed|
|Ignition||Must be Honda Style
All Honda Coils are allowed
|Ignition Wire and Boot may be replaced||No spark intensifiers||Any Spark plug and any timing allowed|
|Balancer||Must be present||Must remain in stock condition||May be modified slightly for rod bolt clearance||Machining allowed|
|Bearings||May be replaced with similar style
No self-aligning bearings
|No Ceramic bearings||NA||NA|
|Bolts||All bolts non tech besides Head bolts. Head bolts must remain stock!||Studs allowed||Safety wire on bolts is recommended||NA|
|Gaskets||Gaskets must remain stock styles. No solid aluminum or copper gaskets allowed. Sealant allowed||Minimum 1 gasket required on Cylinder head and side cover||Sealant only on the exhaust manifold flange is allowed||NA|
|Valve Cover||Must be used. Can be modified to accept permanent fitting to prevent leaks||Stock Honda style only||NA||NA|
|Starter||Must use an electric starter||Block may be machined to accept starter||NA||Machining is allowed|
|Sheet Metal||Must use factory shroud around flywheel. Top cover optional. Lower head cover optional.||Must use permanent non-rotating flywheel screen bolted to housing||Screen may be of any RIGID design to prevent a safety hazard||Holes in screen may be taped or non existent. Hole may be cut in center for electric starter|
|Cylinder Head||Any Honda factory cylinder head may be used! No porting or grinding in ports allowed. Small port heads have some factory grinding that is tolerable.||Surfacing to spec is allowed for thickness: Min 3.725”. No addition of material in ports!||Valve Seats and Valve guides may be replaced. Guides may have liners inserted.||Guide must be inserted completely to stop ring. Must use dowels to block.|
|Block||Honda GX 390 only!
Any Honda GX 390!
Can be bored up to .030”oversize with wear and clearance
|Welding or epoxy for repair is allowed. Welding to plug governor holes or oil alert holes is allowed.||May be sleeved||Deck may be machined to a piston pop up of MAX: .005”
|Carburetor||Tillitson HL360A with manifold ( manifold non tech)
Stock Honda style ( stock appearing rules ) with epoxy
|No Go: Venturi=.945”
|No pressurized fuel systems!||No other tech on carburetor|
|Air cleaner||Any air cleaner system allowed and recommended!||Must be passive||No other rules||NA|
|Fuel Lines||Must be rigidly secured at all connections.||Must be in good working order!||Fuel Filter recommended||NA|
|PCV system||Must route all crankcase ventilation vapor to canister||Ventilation can originate anywhere on block as needed||NA||NA|
|Exhaust Pipe||Pipe must be securely supported and attached. Safety wire should secure bolts from manifold as well as tie pipe to car in case of a breakage.||Length, size, and material are non tech.||May use EGT system||May be used without gasket. Any support is allowed.|
|Oil||Any oil besides an oil containing “Hot” additives.||May not be leaking onto racing surface||NA||NA
87- octane to 110 race fuel allowed
No additives or dangerous oxidizers allowed. Fuel must be able to pass all standard fuel Digitron standards, hydrometer, as well as water tests
|No methanol or alcohol
No blending of these fuels into your race fuel
|NA||No poisons or banned chemicals in fuel!|
Engine Tech Procedure
The Purpose of this document is to detail a teardown procedure to assure fairness and a level playing field. The motor being described is a Honda GX390. This procedure covers what is acceptable from a technically measurable standpoint and from a Spirit and Intent rule. Cheating, or attempting to navigate around the rule set mentioned here, will be seen as probable cause for disqualification for the event currently being participated in. All measurements will be exact to the TOUSANTH of an inch or the THENTH OF A GRAM for weight. A tolerance of up to .001” of an inch in critical and .005” inch in non-critical measurements, and up to 1 gram on weight, can be applied by the technical inspector during teardown. This may allow a mercy rule for differences between measurement devices and is intended to be applied to promote fairness. Any other item in question can be compared to a known Honda production part or a “Suitable Clone part” that meets all specifications listed. The inspector must carry a 1.000” zero gauge and a tare weight, to show conformity of measuring equipment if concern may arise.
Tear Down Procedure:
Inspect visually on and around engine to for leaks and or visual safety issues. Check to assure throttle linkage is in working order and secure.
Check to see that the correct make and model of Honda engine are used. GX 390 block only.
Check to see if safety seals are intact and in an unaltered state. Any evidence of tampering is immediate grounds for disqualification.
Check records with the technical director to see if engine info and seal numbers match MASTER LOG.
Visually inspect air filter for and securing devices to assure safe working order. No filter also allowed.
Use No GO gage in carburetor venturi for correct corresponding carburetor.
Tillitson: BORE 0.945” VENTURI: 1.060”
Honda: VENTURI 0.960”
If NO GO Gage enters carburetor, competitor is deemed illegal.
If not, the carburetor is removed, and the bore is checked with no go gage (Tillitson).
If PASS, Valve cover is removed to inspect the valve train and lift.
Visually inspect to see if springs are single coil and check to see that rockers are stock type.
Install dial indicator to check max valve lift at push rod side of rocker. Zero indicator and assure the lift is no more than 0.265” on both the intake and exhaust.
If PASS, install a degree wheel to check cam duration. Zero wheel and check for no more than 260 degrees of duration at 0.050” lift on both the intake and the exhaust.
If PASS, the competitor may be deemed legal, and tech may be completed. If the technical director wishes to do a complete teardown, the following further steps should be taken.
Remove cylinder head and check minimum thickness to 3.725” in three places. Check to see if ports are stock and in stock condition.
Check to see if stock valves are used and if weight of each is within spec. Inspect the push rods for stock length and configuration. Inspect for stock style retainers (Non-Automotive) Required.
Install a long reach dial indicator and zero at top dead center. Revolve the motor in direction of rotation and check stroke. Stock stroke must be used. Check Piston Pop up for no more than 0.005” at center or wrist pin parallel and directly above the wrist pin.
Remove piston and inspect to see it is Stock Honda Dished style piston and check dome profile compared to specs.
Remove wrist pin, rings, circlips, rod, camshaft, balancer, and lifters and visually inspect for modifications. Check the minimum weight on these items.
Check the flywheel and ignition system. Stock Honda Flywheel minimum weight is 11 pounds, 10 ounces. Any Honda or clone coil may be used along with any coil wire and boot. Factory fan must be used. Spark plug non tech. Timing Non-Tech.
Check to See that Valve cover and sheet metal are being used and are in stock condition.
Check Oil to see if it passes flame test.
Check Fuel to see if it passes Digitron or Take Sample to Send to lab.
If all above rules are passed, Competitor is Deemed Legal.
If not, Competitor is Deemed Illegal and is Disqualified.