Kfm 112

[estepec]

Help! Troubleshooting low power in KFM 112. Can't get past 2400 rpm static. Not the prop. Anyone know the default factory settings for this carburetor? Thinking this may be a to lean mixture. Anyone have other suggestions on troubleshooting 500 rpm to low on static? Thanks much all.

[DesertFox4]

No experience with that engine sorry. Are you sure your tachometer is accurate? We have this discussion sometimes on the Rotex powered aircraft having tachs that read wrong. Hope it's that simple.

[estepec]

I wish it were simple as RPM gauge. I can't get off the ground. 2400rpm took me out 1,000 feet and still not airborne.

[KFfan]

Have you investigated a relatively inexpensive instrument by the name of TinyTach?

[avidflyer]

My though is to tie it off, run it for a bit at full throttle, maybe a minute or more, kill the ignition without moving the throttle, and when it stops, have a look at the plugs. That should give you some idea about the fuel mixture at full throttle. Another thought on checking for to lean is apply the choke, and if it speeds up it wasn't getting enough fuel. Jim Chuk

[Dave S]

EStepec,

I have never laid a wrench on a KFM 112; however, I can offer some ideas in the blind on troubleshooting. Not saying any of this is what you have; but just some ideas. Jim Chuk's idea about testing with the choke for a lean condition is a classical and quick method.

1) Did the engine run fine before this problem developed? Possible looking back to what may have been done, what might have happened, what was changed when it started behaving badly. Going back and checking those items might be useful. Assuming Compression & Ignition are up to snuff......

2) Is the engine running smoothly while not developing full power? If so - whatever the problem it is not likely related to one cylinder.

3) Not getting enough fuel or air; or, getting too much...lean or rich...either can reduce power. If you suspect a lean situation.....consider anything from the fuel tank to the cylinders (obstructions at the finger strainer, fuel line, a mis-algned fuel valve, fuel pump if you have one, gascolator, strainer, any hose swelling or kinked fuel tubing) If the engine burns 4 1/2 gallons per hour, will that rate of fuel delivery through the fuel system occur at the carburetor inlet? Maybe a flow test will provide some insight to tha problem or rule it out. Reduced fuel flow less than the engine consumption rate will definitely affect top end.

4) I don't know if you have a mechanical fuel pump; but, while they wear slow (one failure mode) - a low fuel pump output will affect the high end first and comes on very slowly over time. Sometimes the poppet valves on a fuel pump will stick which can occur quickly and mess up fuel flow (a second failure mode). A fuel pump diaphragm rupture? (another failure mode) Is the throttle valve opening fully? Any obstructions at the air intake/filter or a loose SCAT tube that might be obstructed. Backpressure - is there anything obstructing the exhaust system?

5) Did any bird or vermin decide to crawl into the induction system? - not likely unless the air filter or screen was off the engine for a long time.

6) Then there is all the carburetor internal stuff - plugged jets, inlet valves - which can happen rapidly or slowly.

Wishing you good luck; and, be interesting what you find to be the problem.

Sincerely,

Dave S

KF 7 Trigear Flying
912ULS Warp Drive

S Paul, MN

[estepec]

I found my problem with the low rpm. Bad ignition system. Both the electronic and artic ignition fail to fire on one cylinder. Anyone have any ideas in suitable replacements?