JAG
Engines
Ryobi 31cc Long and
Short Shaft Conversions
1.
Remove
plastic breather cover over carburetor.
2.
Loosen
screw that holds throttle line in place on carburetor.
3.
Remove the
single screw that is inside front of the clutch housing.
You need to use a good medium size flat screwdriver with the sides ground down so
that the driver will fit inside clutch’s front opening. You can also use a star wrench but the screwdriver
works well. Place a large screwdriver (or a
medium size flat file) in the plastic engine cover and let it go into the flywheel fins. This will stop the engine from turning while you
unscrew the clutch. Note that all screws have
right hand threads.
4.
Use a pipe
wrench to unscrew the clutch from the engine. Again,
use a screwdriver (or flat file) to stop engine from turning.
5.
Remove the
5 screws on the front gray plastic engine cover to remove cover and black plastic handle. Pull the housing off with the throttle line
attached.
6.
Remove the
2 screws that hold the carburetor and choke assembly.
Remove the carburetor. Disconnect the
gas lines and carburetor gasket. We suggest that you do not try to enlarge the bore of
the carb. It leans the gas out too much in
many cases and adds little to the performance.
7.
Remove the
plastic back-plate with reed valve. Be very
careful to not damage the gasket. You may
wish to run an Exacto knife blade around the engine between the gasket and the metal
engine to make certain the gasket does not get broken.
Snap off the primer bulb by pushing the two tabs together on the back side of the
bulb assembly and push through opening. (engine
will not run if gasket is broken)
8.
Remove
muffler. The two screws are usually very
tight. A wrench here works better than a
screwdriver. Save the gasket for
re-use.
9.
Remove
flywheel by putting a large screwdriver between the engine and housing and the flywheel
and twist the driver. Turn the flywheel to
two or more positions and repeat twisting the screwdriver.
Don’t loose the small key on the shaft that locates the flywheel timing. Use a ¼” drill to open the holes in the back
of the flywheel where the steel pins are located. Force
the pins out with a punch and hammer. Now the
flywheel is ready to be faced off on a lathe. This
is optional. Balance the flywheel.
10.
Remove the
coil with the spark plug wire attached.
11.
Remove the
4 star head screws that hold the front plate to the engine.
You will need a star type wrench for this operation.
Sears should have a set in their stores.
12.
Cut excess
material off the black plastic back plate. You can use a scrollsaw or a band saw. Use
sandpaper or a file to clean up edges. Then
check the reed opening by placing a 1/8" drill rod between the stainless steel reed
and the reed stop you might have to bend the reed stop with a pair of needle nose pliers
so the 1/8" drill rod (or music wire) will pass through. This will give you the correct reed opening.
13.
Have JAG Engines
or other machine shop turn
down the flywheel to minimum thickness. Only
lightly face off front of flywheel at shaft opening.
14.
Purchase
from JAG Engines or other source the parts that you
may need for conversion.
15.
Assemble
motor mount and back-plate to the engine using the four 10-24 x 5/8” socket head
screws. Make certain what the one low land on
the back-plate is built up with a washer of even thin card stock cardboard or paper so
that when the screws are tightened they don’t distort the motor mount. We normally put the back plate in a lathe and face
off the backside to eliminate this problem.
16.
Attach the
carburetor with choke assembly using the spacer between the carburetor and the back-plate
with a gasket on each side of the spacer. Gaskets
can be made from card stock or purchased from JAG Engines.
The butterfly on the carburetor must be next to the engine back-plate. (Note: the
needle valves must be facing toward the bottom of the engine - opposite the cylinder)
17.
Mount the
flywheel making certain that the key is in the key-way.
18.
Mount the
coil to the engine using a business card between the coil frame and the magneto part of
the flywheel. Tighten the coil mounting
screws. Remove the card stock and the coil
will be perfectly adjusted. The ground wire
from the coil can be hooked up using a stop switch to ground to the engine.
19.
Place the
prop drive on the shaft. Place a 16x8 to 18x8
prop, prop washer and nut to complete the conversion and you are ready to run the engine! Make certain that the throttle arm can be
completely retarded. Some carburetors require
you to file off the throttle stop.
20.
You may
use the bulb pump to prime the engine. The
angled inlet pipe on the carburetor is connected to the clunk line on your tank. The bulb pump line goes to the straight inlet pipe
of the carburetor and goes to the muffler pressure line bent to bottom of your standard
R/C Tank. A third line that can be closed off
with a screw in the line is used as a fill/vent line. If the bulb primer is not to be
used, close off the straight inlet pipe with fuel line and screw to plug the line. Choke engine to prime. A standard electric starter works well to start
this engine. It’s hard to turn the prop
fast enough to get a good spark when propped by hand.
If using a starter, you may not wish to use the bulb primer. Just choke it while the starter is running and it
should start immediately.
(Note:
the short shaft Ryobi engines convert the same as the long shaft engines except
there is no clutch to remove and they use a different prop driver and nut. When converting to a short shaft glow engine, the
long shoulder nut that held the flywheel in place is reversed to hold the glow prop drive
washer and prop to the engine. You must first
cut the shoulder nut square end off leaving about ¾” shaft on the nut. Then run a 5/16-24 tap through the entire shoulder
nut. Drill out the prop and prop washer to
match the outside diameter of the shoulder nut. Do
not over tighten this nut on the engine. We
have had some guys break the shoulder by doing this!
The Ryobi muffler is good but creates
much backpressure and reduces performance considerably.
The JAG Engines investment cast muffler is lighter and
allows maximum prop RPM. Mufflers do make a
big difference. The investment cast muffler
is now available for $38. This unique
muffler will rotate 360 degrees for optimum pipe angle and will accept a smoke system! This muffler only weighs 4 ounces! A smoker add-on is coming soon.
We wish you much success with your
conversion and have many happy hours of flying with your new engine! This Ryobi converted engine will fly many planes
up to 20 lbs depending on wing area and loading. The
first plane to fly with this engine was an Ace Big Bingo at 18 lbs. The Dynaflight PT-19 and Lanier Stinger 120 would
also be excellent choices. Other good choices
are the Stream Akro Pro 180, the Midwest Giles 202, Bridi Killer Bee, Cubs and Citabrias
or any plane with about an average 80” or larger span and about 12 lbs to 18 lbs
weight. We know of a 23 lb Cub on floats that
flys very well off water! Enjoy………
Click here to email JAG Engines
Snail mail:
JAG Engines
16073 Muscatel
Hesperia, CA 92345
(760) 244-7270
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