I've got an issue with an OS 61fx that I'm hoping you guys can throw some suggestions at. The engine doesn't get run very often and sat for about 8 months with after-run oil (i think). Now, the engine will turn over with little to no issue and idle fine but will sputter and die when i get to 1/2 throttle. Should note that it's a new fuel tank and lines (H9 alpha 60). I've gotten it to go full throttle maybe twice out of about 15 times and it will last for about 10 seconds. Usually though, no matter how slowly I increase throttle, it starts to sputter at 1/2. I've set the high-end back to default (open about 2.5 turns) and tried to tweek to get it to let me go to full throttle but no luck. I've changed the glow plug, no luck. I HAVE NOT messed with the low-end needle. It seems to be getting fuel thru the line and there doesn't appear to be bubbles coming thru or excessive vibration. any ideas? I'm going to have another go at it this afternoon.

Thanks in advance
J

That's what I'd mess with, turn it in 1/8 a turn and see if the mid range issue clears up or improves, and adjust it more if you see that improvement until you get a fast response from idle to full throttle.

The fact it runs and idles shows the 8 month storage didn't really do anything. I've had
planes sit for years and fire off first try.

I don't know if it applies to this OS or not, but some OS engines had the remote needle valve assy mounted to a cast part of the back plate. Heat transfer caused the equalivent of vapor lock in the fuel and bad running. An extra cost OS change later fixed the problem.

Another OS issue I have experienced is the plastic needle valve housing cracked and allowed air to get in the line from the valve to the carb.

Or, maybe the high speed needle jet is clogged with debris or congelled oil.

Just because the tank is new, does not mean it is automatically without fault. Check to make sure all lines are clear and with no breaks or holes.

Sincerely,

Richard

It just sounds like it is running a little rich. The factory settings of both needles are usually on the rich side so that one can get the engine running, after that you need to set both needle to adjust for you specific fuel, plug and daily weather changes. Not messing with the needles is not an option, this is what makes the hobby.

This here is what I would suspect is the problem.



So many modelers store engines for extended periods and then expect that they will start and run normaly. Our glow fuel causes all kinds of problems if it is not flushed out and then allowed to dry into a congealed slime. If you flush the engine and carb with sraight methanol, dry and oil it with air tool oil BEFORE storage, it might run well right off the bat when it is put back into service.

thanks guys....looks like a little tweaking on the low end has it running better....didn't get time to mess with it much but I can at least transition to full throttle and not have it sputter....just gotta get it to idle smooth and should be all set.