Round Bottom
Round Bottom
Garden Tractor Pullers
20 HP TWIN STOCK ALTERED RULES -"2001"
1. Four-cycle, two-cylinder, 20HP engine allowed. Must be lawn and garden type, gas only. Must retain stock stroke, stock bore and stock valve size for the engine as offered from the factory.
2. One single-barrel carburetor with one-inch max Venturi allowed. Must be of engine manufacturer type - i.e. Kohler on Kohler, Briggs on Briggs etc. NO FUEL INJECTION. NO STROKER KITS. NO OVERHEAD CAM. Chokes may be removed.
3. Carburetor may be mounted to intake with no more than a one-inch spacer (Including gaskets).
4. Stock Heads must be factory engine type Kohler on Kohler, Briggs on Briggs, etc. No Head plates. Porting and Polishing okay. No homemade or recasted heads.
5. Camshafts may be ground. Valve lift .415 measured at valve on O.H.V. and 330 valve lift on Flathead engine any duration.
6. Clean up on top of block okay.
7. Steel fly wheel mandatory.
8. Spark plug to remain in stock location.
9. Air cleaner or velocity stack okay.
10.
Gas specific gravity of .750 maximum or check with dielectric tester. No pressurized fuel tanks, no nitrous
oxide, or no alcohol.
11. Kill switch
required.
12. Electric fuel pump okay - must be wired to key switch and kill switch.
13. No homemade intake manifolds - factory intakes only - Briggs on Briggs, Onan on Onan, etc.
14. Stock ignition parts only - no booster coils.
15. Tractor must have garden tractor rear end with reverse - locked rear ends okay.
16. Tractor must run factory-looking hood and grill.
17. Wheelbase - 52 inches maximum.
18. Length is up to 7 feet from center of rear axle to the farthest point forward; total max width of tractor is 60 inches.
19. Tractor must have fenders that cover at least one-half of the tire on the top and front of tires must have platform for feet.
20. Tractor must have at least a 3" high restraint to keep driver from sliding off backwards.
21.
Weights cannot be more than 24" behind center of rear axle.
22.
Maximum tire size -26x12x12. Bar tires can be cut for dirt (turf tires only on
blacktop). 23.
Must have shields and guards over belts, chains and clutch assembly. 24. Must have wheelie bars, not more than 5 inches from the ground up-at least five inches from back edge of tire. 25.
Things we will "tech" - bore, stroke, cubic inches, valve lift at valve, valve size head diameter and carburetor venturi. 26.
Any engines not listed on the motor specification sheet will need to show
factory-published specifications for the engine in question to assure it is a 20
HP engine and is subject to approval by the Tech Committee. 27.
There will be a $100.00 charge for a protest. 28.
All other general and club safety rules apply. Tech Committee: Chuck Kelly (614-891-1846), Trent Strauser (740-477-2493), and Carl Herb (740-927-5595) Motor
Specifications Kohler
Command Engine 20 HP O.H.V. Kohler
Magnum Engine 18 HP Flathead Kohler
Magnum Engine 20 HP Flathead Onan
Engine 20 HP Flathead Honda
Engine 20 HP O.H.V. Kawasaki
Engine 20 HP O.H.V. Briggs
& Stratton 18 HP Flathead
Displacement Bore 3.03 in. - Stroke 2.64 in. = 38 cu. in.
50 mm over stock bore 3.05 -2.64 = 38.57 cu. in.
Stock valve size head diameter-intake 1.31 in. -Exhaust 1.16 in. -Rocker Arm
Ratio 1.5
Displacement Bore 3.12 in. - Stroke 2.75 in - 42.18 cu. in.
.030 in. over stock bore 3.15 - 2.75 = 42.86 cu. in.
Stock valve size head diameter - Intake 1.375 in. - Exhaust 1.375 in
Displacement Bore 3.12 in.- Stroke 3.06 in. = 46.98 cu. in.
.030 in. over stock bore 3.15- 3.06 = 47.69 cu. in.
Stock valve size head diameter - Intake 1.375 in. - Exhaust 1.375 in.
Displacement Bore 3.25 in.- Stroke 2.875 in. = 47.7 cu. in.
.040 ill over stock bore 3.29 - 2.875 = 48.9 cu. in.
Stock valve size head diameter - Intake 1.371 in. - Exhaust 1.113 in
Displacement Bore 3.0in.- Stroke 2.68 in. = 37.7 cu. in.
50 mm over stock bore 3.02 -2.68 = 38.4 cu. in.
Stock valve size head diameter - Intake 1.24 in. - Exhaust 1.08 in.
Displacement Bore 2.99 m. - Stroke 2.68 in. = 37.62 cu. in.
75 mm over stock bore 2.93 - Stroke 2.68 in. = 38.37 cu. in.
Stock valve size head diameter - Intake 1.22 in. - Exhaust 1.06 in.
Displacement Bore 3.44 in.- Stroke 2.28 in. = 42.3 cu. in.
.030 in. over stock bore 3.47 - 2.28 = 43.1 cu. in.
Stock valve size head diameter - Intake 1.380 in. - Exhaust 1.235 in.
