435 NE Spruce Ct * Redmond, OR 97756 * U.S.A.
Phone:  (541) 923-4009
Email: carrprecision@centurylink.net

RC Aircraft Engines
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STRING TRIMMER ENGINES
The string trimmer type engine makes an excellent 1/4 scale model power plant.

Model Engines Conversion Kits


Homelite 25cc with kit

Displacement: 25cc/1.5ci * 30cc/1.8ci
Propeller: 18 X 8 * 18 X 10
Weight:   4 lbs.


Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $45.00

Weedeater 18cc with kit


Displacement: 18cc * 21cc * 24cc
Propeller: 16 X 6 * 16 X 8
Weight:   3 lbs. 3 oz.

Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $45.00

McCulloch Engine with kit

Displacement: 28cc/1.7ci * 32cc/1.9ci
Propeller: 18 X 8 * 18 X 10
Weight:   4 lbs. 9 oz


Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt,
magneto mount plate.                                           

Price:   $70.00

Ryobi Engine with kit

Displacement: 28cc * 31cc/1.8ci
Propeller: 18 X 8 * 18 X 10
Weight:   3 lbs. 15 oz

Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and (for   
short shaft) bolt or (for long shaft) nut, carburetor     
spacer with gasket.                                               
Price:   $58.00

Honda GX25 Engine with kit

Displacement: 25cc/1.5ci
Propeller: 18 X 8
Weight:   4 lbs. 6 oz


Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $75.00

Honda GX31 Engine with kit

Displacement: 31cc/1.8ci
Propeller: 18 X 8
Weight:   4 lbs. 14 oz.

Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $75.00

Honda GX35 Engine with kit

Displacement: 35cc
Propeller: 20 X 8
Weight:   5 lbs. 12 oz


Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $75.00

Shindaiwa 25cc Engine with kit


Displacement: 25cc
Propeller: 18 X 8
Weight:   4.5 lbs.

Basic Conversion Kit:
 (for those who want to do their own conversion work:
motor mount w/ screws, prop hub, washer and bolt.
Price:   $75.00


Conversion Parts
(available for those who want to do their own conversion)
    2-cycle engines
  • Homelite, Weedeater, McCulloch motor mount with screws ------------ $ 20.00   
  • Weedeater 25cc motor mount with screws and spacers ---------------- $ 25.00   
  • McCulloch magneto mount plate  ------------------------------------ $ 25.00   
  • Ryobi 31cc 2-cycle motor mount with screws  ----------------------- $ 25.00   
  • Prop hub, washer and bolt or nut ---------------------------------- $ 25.00    (specify if your engine is short or long shaft)
  • Ryobi 31cc carburetor spacer with gasket  ------------------------- $ 8.00   
  • Flywheel machined and balanced  ----------------------------------- $ 20.00   
  • C&H electronic ignition system fixed timing ----------------------- $ 130.00
    * Complete System = ignition, prop hub, timing clamp, pulse switch, & magnet          
  • Homelite, Ryobi B&B muffler (aluminum dual pipe) ------------------ $ 32.00    Mufflers for other engines available
  • Homelite, McCulloch, Weedeater big bore carburetors --------------- $ 48.00   
  • (Homelite) "Twister" big bore manifold with gasket ---------------- $ 12.00   
  • Resistor spark plug (helps reduce radio interference) ------------- $ 4.00   
  • Velocity stack - the correct size for your engine, recommended on all engines for improved performance ----------------------- $ 12.00    4-cycle engines
  • Honda GX31, GX25, GX35 motor mount  ------------------------------- $ 35.00   
  • Honda prop hub, washer & bolt (stock ignition) -------------------- $ 35.00   
  • Honda flywheel machined and balanced ------------------------------ $ 30.00   
Info Package (includes products, conversion instruction & engine dimensions ------- $5.00

Airplanes that can use string trimmer size engines
Photo Gallery


  • 1/4 scale Piper Cub Balsa USA
  • Stinson Reliant SR-9 by Top Flight
  • Hangar 9 PT-19
  • Robin Hood 80
  • Phaeton 90 Bi-Plane Balsa USA
  • Hangar 9 - 1/4 scale Cub

  • Chipmunk 1.20 by Dynaflite
  • Thunder Tiger J-3 Cub ARF
  • PA-18 Piper Super Cub by Dynaflite
  • PT-19 by Dynaflite
  • 1/4 scale Fly Baby by Dynaflite
  • Super Decathalon by Dynaflite


  • String trimmer engines in their stock configuration are restricted on the intake and exhaust. Four easiest ways to improve the performance of your engine are bolt on.
    1. A lighter high performance muffler.
    2. A larger carburetor.
    3. Enlarging your intake manifold to fit a larger carburetor.
    4. Using a velocity stack to improve the fuel/air mixture.

    Homelite with B & B Muffler
    B&B Muffler


    Twister Manifold

    The Twister Manifold for Homelites twists the carburetor clockwise 65-degrees.


    Twister Manifold - $ 12.00
    1. It allows the throttle to work on a horizontal plane
       and makes it easy to hook up the servo throttle linkage.
    2. It gets the idle and high speed neeedles away from the propeller. It is safer to tune.
    3. The choke shaft becomes vertical so in an inverted engine set up, the choke shaft can be easily extended out the bottom of the cowling.
    4. The thickness of the manifold is 1/4" less than a stock manifold, so it is easier to fit under or inside a cowling.


    Weedeater w/ electronic ignition

    This is the Weedeater 21cc Featherlite using electronic ignition.
    It is the lightweight of the gas string trimmer engines. It weighs 36 oz. and is powering an 80" wingspan Hangar 9 Cub.

    C&H electronic ignition system fixed timing- $150.00
    Honda C&H electronic synchro spark ignition system - $230.00

    Electronic Ignition Advantages
    1. Removes 16-ounce flywheel and coil 
       assembly from engine.
    2. Easy to hand start/low idle speed.
    3. Improves high-speed performance.
    4. Electronic ignition unit and battery 
       can be positioned for ideal C/G. 
       Requires a 4.8V 800 MA minimum 
       battery pack


    Ordering Instructions
    We will be glad to take your orders by phone or by mail.
    Call us if you have any questions.
    • For Mail Orders: Send mail orders to Dave Carr   *   435 NE Spruce Ct   *   Redmond, OR 97756

      Please make check payable to Dave Carr.
    • For Telephone Orders: Call (541) 923-4009
    • Ship Engine to:
      Carr Precision   *   435 NE Spruce Ct   *   Redmond, OR 97756


    Shipping and Handling (U.S.A. only)
    Call us or email us for out of state orders.
    • For Kit Parts: US Mail, add $10.00
      UPS-ground, add $15.00
    • For Complete Engine: add $20.00

    We accept cash, check, or money order.



    Email: carrprecision@centurylink.net

    Terms:  Prices and specifications are subject to change without notice.
    Converted engines are new unless otherwise specified.


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    Copyright 2002 Carr Precision
    Last modified: 1/6/2012