OFNA Racing 25,26 User Manual
FORCE 25 OR 26 PULL START
ENGINES
Thank you for purchasing a OFNA engine. We appreciate your choice and know you will enjoy running it. Please
note that theForce information in engine box is subject to change with not notice.
Carburetor Low end and barrel stop screws are pre-set by factory.... Do not change until break-in is done.
NEW ENGINE BREAK-IN
Your OFNA engine is extremely tight when the piston is at the top of the stroke and turning the crankshaft by hand.
This is normal for a new ABC type engine. The piston and sleeve are matched for fit and the top of the sleeve is
tapered for a tight fit. As you run your engine, this tightness should diminish. There is no cause for alarm, because
as the engine warms up, the brass sleeve will expand faster than the aluminum piston and the engine will turn freer.
As with any new engine, there are many high spots and tight fits in the matching process. High spots create hot
spots that must be broke-in. Therefore, the break-in process is very important to provide good service by the OFNA
engine. So, you must run the engine rich (COOL) for the first three tanks of fuel. We recommend using one gallon
of 20% BLUE THUNDER 0R BYRON'S 2000 as break-in fuel. Other break-in type fuels or added oil is NOT
needed. DO NOT OVER REV THE ENGINE WHEN FIRST STARTING, this could break the piston and over heat
sleeve. Let engine run at low RPM for one tank to break-in connecting rod bearing before starting full break-in.
Break-in the engine in the car, by running the engine at a rich setting. Run the car from a slow to fast speed with
short bursts of speed. You need to buildup a little heat in the engine, but not too hot. In a rich setting, the engine
will run cold. In the leaner setting the engine run hot, this is not good yet. Do not heat up the engine too much at
this time. After about one (1) tank, turn the Master Needle Valve, clock wise, 1/8 of a turn leaner or clockwise.
Keeping the fuel tank full, continue the process until you slowly turn the Master Needle Valve, 1/8 of turn each time,
too a leaner point and in which the engine runs at high RPM and power, but still keep max temp. of 250 deg. F. At
this point you must stop, too lean of a setting will heat up engine and damage the piston. A normal operating
temperature is around 220 to 270 Deg. Temperatures of 300 Deg. and above will damage engine and shorten life.
NEEDLE SETTINGS
Master Needle Valve - main control for fuel mixture. Set at 3 to 31/2 turns from closed. Adjust this needle for
maximum RPM and power without being too lean or too hot. Make sure you start at bottom of needle seat!!
Side Carburetor Needle (Low Speed) - This needle is in the center side of the carburetor and provide throttle
response. It is not the idle adjustment. Set FLUSH with the brass sleeve. Turning in is Lean and Out is Rich. Do
not adjust this needle until the Master Needle is set for power and top speed. This will only effect throttle response.
FOR THREE NEEDLE CARBURETORS, DO NOT ADJUST MID RANGE NEEDLE, PRESET BY FACTORY
Barrel Stop Screws - Used for adjusting Idle. Set for 1/16th inch gap to start new engines. You can open more for
faster idle.
USE LONG GLOW PLUG WITHOUT IDLE BAR,
OFNA/PICCO #51007 IS RECOMMENDED
OFNA RACING , 7 VANDERBILT, IRVINE, CA. 92618 TEL:(949)586-2910
#52980
FORCE 25 OR 26 PULL START
#52259
MASTER NEEDLE
ASSEMBLY
#52130-P4/P6
#52140
#52170
#52181
#52240
#10320
#52940
#10330
#52260
#52960
#52250
#52950
#52900
#52220
#52218,
Short#52189
#52016 -.25
#52019 -.26
#52018 -.25
#52020 -.26
#52017 -.25
#52021 -.26
(USE TWO PER ENGINE.)
#52042 -.25
#52045 -.26
#52972 - PIN
#52990 - CLIP
#52060
#52074
#52920 - 13mm
ENGINES
#52091
#52600
#52099
#52273
#52930
FORCE .25/.26 PULL START
OFNA# Factory # DESCRIPTION RETAIL
52016 CH2501-OFNA HEAD, TALL BLACK, .25 34.95
52018 BR2501-1 HEAD, BUTTOM REPLACEMENT, .25 19.95
52017 HW2503 HEAD, SHIM, .25 1.95
52042 CP2504/5A CYLINDER SLEEVE AND PISTON, .25 99.95
52019 CH2501-OFNA HEAD, TALL PURPLE, .26 34.95
52020 BR2501-1 HEAD, BUTTOM REPLACEMENT, .26 19.95
52021 HW2503 HEAD, SHIM, .26 1.95
52045 CP2504/5A CYLINDER SLEEVE AND PISTON, .26 99.95
52060 CR2106 CONNECTING ROD (ALUM. 7075S) 14.95
52074 CK2507 CRANKCASE, FORCE .25/.26 44.95
52273 CS2108T CRANKSHAFT, SG, PULL START, .25/.26 75.95
52090 FM-2109 REAR BACK COVER 6.25
52091 RS-12/17 REAR BACK PLATE UNIT, PULL START 24.95
52098 RS-18/19 SPRING AND PIN, PULL START 3.95
52099 RS-1/11 PULL START UNIT W/ ROPE 24.95
52100 2110 CARBURETOR SET PIN 3.25
52110 2111 SLIT METAL CONE 2.95
52120 2112 DRIVE HUB 3.25
52130 2113 CARBURETOR BODY, P4 / P6 11.75
52131 21131(7mm) CARBURETOR COMPLETE, 7mm 61.95
52140 2114 THROTTLE BARREL 6.75
52150 2115 THROTTLE NEEDLE 3.75
52160 2116 SPRING, THROTTLE NEEDLE 1.25
52170 2117 BOOT, THROTTLE 2.50
52181 2118ST BALL END, THROTTLE NEEDLE 5.95
52190 2119/20 BARREL STOP BASE AND NUT 2.25
52219 2121 BARREL STOP SCREW 2.25
52220 2122 LOW END NEEDLE 4.75
#52090
#52980
52230 2123 WASHER, ALUMINUM, 1 PC 0.95
52240 2124 FUEL SUPPLY NIPPLE 2.50
52250 2125 MAIN NEEDLE SEAT 4.25
52260 2126 MAIN NEEDLE 3.75
52900 B-1 BEARING, OUTSIDE, 607Z 5.95
52920 B-3 BEARING INSIDE, 13mm 18.95
52930 L-1 SEAL, REAR COVER 1.75
52940 L-2 SEAL, CARBURETOR 1.25
52950 L-3 SEAL, LOW END NEEDLE 0.95
52960 L-4 SEAL, MAIN NEEDLE 0.95
52972 P007 PIN, PISTON, .25 2.95
52980 FMS-1/2 SCREW SET, 8 PCS 2.50
52990 FMW-1 CLIPS, G, 2 PCS. 1.95
OFNA RACING , 7 VANDERBILT, IRVINE, CA. 92618 TEL:(949)586-2910
Loading...