Have a Sachs 4.2 engine. It was running great, but had a couple deadsticks with it. Seems that when you came off the throttle under high airspeed it would die. After some searching I found I needed to add a nipple to the carb plate and run a fuel line form it to inside the fuse. Supposedly this is common and the air through the cowl would press on the opening and lean the engine and it would quit.

So, I added a nipple per instructions and ran the fuel line inside the fuse. I started the engine and ran it for a while from idle through full throttle. Ran great!

Took the plane to the field and it ran like crap on the ground, unlike it ran in the garage before I went to the field. Thought maybe the nipple/line I added was the cause, so I removed it and it still ran like crap. Adjusted the low needle to try and get it to run better but no luck. Under any needle setting, it either ran like crap or didn't run at all.

Basically it starts and then either quits immediatly (like it's too lean) or runs for a little bit, but runs very rough (like it's rich). When adding throttle it increases RPM's slightly (no matter if adding a little throttle or WOT) but still runs very very rough (as if really rich). It will sit and run rough like this for as long as I want it to. After a while I get some darker smoke out the exhaust (again, like it's real rich). But, leaning just causes it to not start at all (fires but dies immediately).

Brought it home, took the carb plate off to see if the nipple was pressing on the diaphram and it was not, remove the nipple allthogether - no different. Checked the fuel filter, looked good, cleaned anyway, no better. Checked the plug, looked good, cleaned anyway, no better. Messed with the needles with it running and it made no difference until I got it lean or rich enough to get it to quit. Adjusted the timing in both directions and it made no difference all the way until it would not start anymore.

I am really stumped on this one. Not sure what else I can try and I am looking to the experts for some help. I don't think it matters if you have a Sachs, DA, 3W, whatever. I am looking for some general tips and ideas on generally what may have happened and what I am doing wrong.


Thanks in advance for all your help!

Posted this on RCU also and someone mentioned to check the ignition battery. Seemed to be ok, took a charge, tested ok w/ voltmeter - replaced it anyway and it ran great again. Never seen that before, but the battery must have had some issues.