ENGLISH
20
There are a few things you must do to ensure proper operation of your Tomahawk radial engine.
Occasionally, you will need to adjust the valves. Adjust the valves the first time after one hour of
engine run time. After the first hour, monitor the valve lash and adjust the valves as needed. Adjust
the valves when the engine is cool. The lash is set at 0.1mm–0.15mm at the factory.
MAINTENANCE
1.
Place the engine in a position (on or off your airplane)that allows you easy access to the valves
on all the cylinders.
2. Remove the spark plugs from all the cylinders. It is much easier to determine Top Dead Center
(TDC) without the compression caused by installed spark plugs.
3.
Attach a propeller or other turning device (such as a short block of wood with the appropriate
hole for the crankshaft) to the crankshaft and tighten it so you can easily rotate the crankshaft
throughout this process.
4.
Start with the number 1 cylinder (this should be the upright cylinder above the Tomahawk
logo).
e.
Rotate the crankshaft counter-clockwise and observe the pushrod movement.
f.
Note when you see the exhaust and then the intake pushrod move up to open the valves.
This will occur during one rotation of the crankshaft.
g.
When the piston reaches the top of the cylinder during the next rotation, you are at the
TDC of the compression/firing stroke.
h.
Position the piston at TDC of the compression/firing stroke. It is helpful to place a short
piece of wooden dowel. (Don’t use steel, as you can mar the inner surface of the cylinder.)
5.
Use a feeler gauge to check the valve lash between the rocker arm and the top of the valve.
a. We recommend setting the valve lash as close to 0.15mm as possible. If the valve lash is
between 0.10 and 0.15mm you do not need to adjust the valve lash. The settings for
the intake and exhaust valves are the same.
b. If adjustment is needed, adjust the valves by loosening the locking nut and adjusting the
screw until you can just feel the drag of the 0.1 feeler gauge as you pull it between
the valve and rocker arm.
c. Tighten the locking nut and recheck the valve clearance. Sometimes when tigh tening the
nut the adjustment will change slightly.
6.
Because the cam gear of our engines is a shared cam gear with all the cylinders and rotates at a
1:4 ratio, there are actually 4 different positions on the cam gear that need to be checked. Re
-
peat step 4 & 5 above four more times to check each of these positions, rotating the crankshaft
two full revolutions between each check. If you find that the valve lash is smaller, then readjust
that valve. If it is greater, do not readjust the valve. A little loose is safer than too tight.
7.
Now move onto the next cylinder in a counter-clockwise direction and repeat steps 4 through
5. Do this for all 5 cylinders.
Congratulations. You have now completed the valve adjustment process. This maintenance
should not be required again for another 10 hours of running time.
TOMAHAWK RADIAL VALVE ADJUSTMENT GUIDELINES
WARNING:
Use a high quality gear oil to lubricate outer parts of the valve train at the beginning of
each flying day. For the first 15-20 flyings days move the exhaust valves by hand and lubricate them
properly. Use high quality machine oils and no grease. The tappet base should be lubricated every
fifth flying day .
