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THROTTLE/CARB PROBLEMS ON A VariEze
Enclosed is requested survey
information on our VariEze, N222HK, SN 222. We are the original builders and continue to
maintain and fly this thoroughly enjoyable aircraft. During our eightyears of such, 222HK
has proved to be remarkably free of serious problems. It has flown five times Utica, NY to
Oshkosh. There are a couple of things I would like to relate, however.
The most sever problem which I can recall was with the throttle carburetor control. Very small diameter portals built into the carb (Marvel Shebler mounted on a Continental 0-200) became clogged to such an extent that they created hydraulic back pressure on the primer piston. The result was very sluggish response of the actuator arm on the carburetor with the following consequences: Failure to provide adequate prime on opening the throttle, this made for hard starting. Failure of the two springs to quickly move the throttle arm to full open on demand, - a serious problem in the event of a go around. Failure of the cable to push the throttle arm to full open.
During servicing the aircraft, I noticed when opening the throttle using the control handle the cable actually buckled up and the arm did not move Probably with the engine running vibration caused the arm to move slowly and would only be noticed in the event a sudden surge of power was demanded. I believe the change was a slow process and very subtle indeed.
Disassembly of the carburetor revealed the clogged portal and the fact that the fuel injection piston could not force a stream of fuel into the carburetor during prime. I do not know what material caused the clogging, perhaps a small residue of epoxy.
Whenever the cowl is removed, a simple check can be made to insure that the carburetor arm responds quickly when the throttle handle is advanced. It may take two people to do this.
A second issue involves small particle fuel contamination which has been virtually eliminated in 222HK by installation of an in-line auto fuel filter. We didn't like the heavy gascolator so installed three low point quick drains and the filter. The filter is a glass enclosed cylinder about I inch dia. x 4 inches long and easy to service. The clear glass allows visual inspection whenever the cowl is removed. We have found particulates such as Teflon, fiberglass and other unknowns in spite of thoroughly cleaning all tanks before placing in service.
As original builders, we greatly appreciate the tremendous job you have undertaken in keeping us informed. We have built two more aircraft, a Kitfox Model I and a Zenair STOL 701. Neither of these can compare with the service we have received from you. Please accept our heartfelt thanks and keep it going as long as possible.
Charles M. Hewison"
EDITOR"S NOTE: We certainly appreciate Charles' experiences, but instead of the in-line auto fuel filter we would recommend a Kinsler inline fuel filter. These are available from:
Kinsler Fuel Injection
The filter assembly, part #9020, costs $85.00 and extra filters, part #9023, costs $8.00 each.
These are quality parts, machined from solid aluminum and have Dash 6 (3/8") AN flared fittings machined on to each end. The internal paper filter is replaceable (Kinsler part #9023) and can be cut apart to look for particulates at each annual. These filters are made for fuel injected ingines and work very well. Mike and Sally, Doug Shane and Dick Rutan are all currently using this in-line fuel filter.