EC Carburetors designed PK-1A Tillotson Stock Carburetor in 2011 for the then AKRA Rules.
The well-known world leader in small engine racing carburetors, Tillotson LTD, has produced their version of the common GX200 carburetor. Tillotson recognized the need to produce a consistent carburetor for the USA clone racing engines. EC Carburetors took the 196cc OHV lawn and garden carburetor and calibrated (Blue-Printed) it for the racing market. The PK-1 carburetor is legal for AKRA and many other racing divisions.
The Tillotson PK-1A fits most of the 196cc 6.5hp Clone Engines, including Honda GX200, Ducar 196, Ducar/Tillotson 212E, Tillotson 196R/RS, Tillotson 212R, Ducar/Tillotson 212E, Predator 212, and BSP 196 and 212 Engines.
The key standard features:
- The venturi is machined to .613" plus or minus .001" very close to the .615" no-go rule. Additional boring is not needed.
- The throttle shaft alignment is made to the centerline of the bore.
- The emulsion tube is of a 24 hole progressive design
- Main jet size .039."
- Low side jet .028."
- Low side air bleed .055."
- High side air bleed .043."
The jetting above is a general starting point for all different types of racing, this combination was base on a stock rule clone using CL-1 camshaft turning a max RPM of 6,100 with 10.8 springs.
If you have a current 2017 built AKRA stock clone engine with a ported head, CL-3 type camshaft 10.8 spring, 37-degree flywheel advance
, and your turning about 7,000 RPM or more, you may find using a .034" to a .037" low side jet and .036" to .039" main jet. Caution: Using this combination your idle may be rough and there is a chance of loading up if it idles for too long.
Minibike racers, we recommend trying the carburetor as is; if idle is too rough, you may need to purchase a .020" low side jet.
NKA 2020 Rules for Carburetors
4.11: Carburetor 40.4. 11.1: Approved Carburetor
Stock Huayi or Ruixing type carb only. There must be a factory edge, not rounded or smoothed over, all the way around the entrance and exit to the venture of the carburetor. It can be compared to a stock carburetor. No extra holes drilled in carburetor anywhere. No sanding or machining of carburetor mounting surfaces.
40.4.11.2: Choke Assembly
40.4.11.2.1: Choke assembly must be in place and functional.
40.4.11.2.2: Choke lever must be stock. Drilling holes to mount choke lever is prohibited.
40.4.11.3: Venturi
40.4.11.3.1: Venturi .608" Must-Go
40.4.11.3.2: .615 Max blade-type No-Go
40.4.11.3.3: Throttle bore .751" No-Go
40.4.11.4: Minimum Protrusion into Venturi
40.4.11.4.1: Huayi: .488
40.4.11.4.2: Ruixing: .478
40.4.11.5: Throttle Shaft
The throttle shaft is .115" minimum thickness; the material is non-tech.
40.4.11.6: Butterfly
The butterfly is .037" min thickness; butterfly screws minimum length 0.305."
40.4.11.7: Jets
The main metering jet and low-speed idle jet are non-tech.
40.4.11.8: Filter/Filter Adapter
40.4.11.8.1: Filter adapter max 1.375" height. No "ram air" Any filter that is open on the end must be covered over with tape or pre-filter that will not allow any air to enter filter from the end of the filter. Air must enter filter from the sides. If this type of filter is used, turn them toward the rear of the kart.
40.4.11.8.2: Grinding or modifying the spacer between the filter adapter and the carburetor is prohibited.
40.4.11.9: Emulsion Tube
40.4.11.9.1: Through-hole maximum ID of 0.066" No-Go.
40.4.11.9.2: Minimum length is 1.092" and must have 20 holes on top; the hole diameter must be 0.036" No-Go. Bottom holes can be either 2 or 4 holes. 81
40.4.11.9.3: The minimum length on the emulsion tube is 1.092".
40.4.11.9.4: The minimum diameter is 0.154."
