684i B4 / TS / QS Engine Manual
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the fuselage. Do not forget to reinforce around this hole.
Important:
This exit area needs to be four times (4x) as large as the intake area.
Propellers
•
Only use propeller brands and sizes that are approved for your engine
•
The propeller blades must be of the same length
•
The propeller must be flat (You can check for flatness by putting the propeller on a level
surface. The maximum difference of the blade heights should be no more than 1/64".)
•
The propeller tips must have an identical shape. This is especially important when using
3 or 4 blade propellers.
•
You must use a drill press to drill your propeller.
•
You must drill the propeller from the rear.
•
A drill guide is recommended, but the propeller washer can be used as a drill template. (Fix
the propeller washer onto the propeller in the center-bore using a bolt and nut. Drill one
hole; put one of the propeller bolts into the hole. Continue until the last bolt is used.)
•
If you cannot hand tighten all of your prop bolts easily then you have not drilled the propeller
correctly. This can lead to sheared propeller bolts.
•
Balancing your propeller is absolutely critical to the health of your engine. You must keep
your propeller balanced. (Propeller balancers are available from DUBRO, and others.)
•
Always remember that when the engine is running every person must stay behind the line
of the rotating propeller; never to the side or the front!
Carburetor settings
Before each engine is shipped it has to pass QC and is then test run. We do a basic adjustment
of the carburetor needles at that point.
front carb.: highspeed needle:
rear carb.:
highspeed needle:
low speed needle:
low speed needle:
Important:
Do not remove the carburetor spring as the spring helps keep the carburetor butterfly
aligned properly. Merely release the ends of the spring so that it no longer holds the butterfly
closed.
