The K&B .45 DF is a high-performance engine, designed especially for ducted fan models.
It is an improved version of our previous, highly successful engine, known throughout the world
for its power and proven reliability, and will provide countless hours of
sport or competition performance if properly handled and maintained.


Part No. 4825


Displacement .4539 Cu. In. (7.44cc)
Bore .850 (21.6mm)
Stroke .800 (20.3mm)
R.P.M.  2,000 - 25,000
Power Output 2.75 HP @ 25,000
Weight 15.8 Oz. (448g).


PLEASE READ ALL SAFETY INSTRUCTIONS! Failure to read, understand and follow these instructions could result in personal injury and/or property damage to yourself or others.

Take a few moments to familiarize yourself with the various parts of the engine. DO NOT DISASSEMBLE YOUR ENGINE! Doing so will void your warranty. No exceptions!

This engine is designed to use our Long Reach Glow Plug (K&B Part No. 7311).
We recommend 15% nitro with 22% oil. A pressurized fuel system must be used to boost the fuel to the needle valve. Install a pressure fitting on the tuned pipe, just behind the apex where the cones join. An in flight mixture control (P/N 9275) is highly recommended for use with this engine.
  • Never place your hand in front of the fan for any reason while the engine is running.
  • Keep rags, articles of loose clothing, or anything that might be ingested, well clear of the duct intake.
  • Always start the engine at an idle throttle setting.
  • Wear eye and ear protection.
  • MAKE PERIODIC CHECKS: After every flight, remove the glow plug and check the coil condition. If it is broken or badly distorted, replace it. The glow plug life will be longer when you achieve a good needle valve setting.
  • After every four flights, check tightness of the engine head and mounting screws, as well as fan and spinner security.
  • After every twelve flights, check the tuned pipe coupler, and tightness of the clamps.

If you are unfamiliar with this line of carburetors or are a new modeler, please do not attempt to start the engine until you have read and understand the following instructions:

1. NEEDLE VALVE SETUP - Locate an area to install the Remote Needle Valve Assembly. This assembly must be in the fuel line between the tank and the carburetor. The line should not exceed five (5) inches in total length.

2. LINKAGE SETUP - Notice the barrel will rotate 360 degrees. Using your radio and trim functions, set the barrel movement for full open and full close. IMPORTANT: THE BARREL MUST CLOSE IN A CLOCKWISE ROTATION. The opening in the barrel spraybar faces the crankshaft.


Note that there are two fuel metering adjustments:

1.    HIGH-SPEED NEEDLE VALVE - This needle valve, located on the remove Needle Valve Assembly, controls all the fuel that comes to the engine, whether the engine is running at high, mid-range, or idle speeds. It does not affect the low speed rich/lean setting. The High Speed Needle Valve’s main function, however, is to meter the high-speed fuel mixture.

2.    LOW SPEED and MID-RANGE ADJUSTMENT - The rich/lean adjustment is controlled by the brass low speed disk located on the side of the carburetor. Using the allen wrench provided, turn the disc clockwise to “lean” the mixture and counter-clockwise to “richen” the mixture. The rich/lean mixture control is set at the factory and may require only a fine adjustment for your application. WARNING: DO NOT RUN THE ENGINE AT A “LEAN” SETTING.


As a starting point for the high-speed needle adjustment, completely close the needle valve (clockwise), then open it (counter-clockwise) three and a half turns. This setting is an average and may require further adjustments. For higher altitudes (3,000 - 4,000 feet), close needle valve approximately 1/2 turn.


All series “94” carburetors must run with exhaust pressure from the tuned pipe connected to the fuel tank.


© Model Engine Corporation of America, All rights reserved.
K&B and the oval logo are Registered Trademarks of Model Engine Corp. of America
Registered U.S. Patent Office

No part may be reproduced without written permission from
MECOA/K&B -- P.O. Box 5 -- Sierra Madre, CA 91025 U.S.A.