OS 50 (not Hyper) starts and occasionally runs Backward

[gobysky]

Many years ago when I used to fly planes, I would richen up the mixture slightly and this backwards running would stop.
Tried that on my Raptor engine but didn't help. Set the idle up a little, but by the time I walked the heli out, it would start running backwards again.
Anyone have this problem ?

[z11355]

almost a sure sign of TOO rich, esp on the low needle

[gobysky]

Well, I guess I'll have to try the other way towards leaner, see what happens. Weather changes so quickly around here, one setting doesn't always fit all.
Last time I flew it was in the 70's. Today it was about 39 degrees. That probably had something to do with screwed up mixture settings.

[Maxists The Baddist]

That happens to me too. I though it had something to do with cold weather. Whenever it happens I would kill the engine and when restarted always went away. Only happens on the first start and stopping and restarting always make it go away so never became a really big problem.

Wow, good to know has something to do with mixture.

[stevehonn]

Cold weather & rich mixture, I even had mine cough and start backwards whilst in flight!

[gobysky]

I think I discovered another reason I was having problems with the way my engine was running. As I was going over the nuts and bolts tonight on my Raptor, I discovered the muffler bolts to be loose. Enough to cause loss of back pressure.

I haven't run it yet since I tightened them, but it seems to me this would have an effect on the engine's mixture.

I guess it would pay to check those bolts more often. I thought I had used plenty of locktite on those bolts, but they came loose anyway.

[JASO']

I had a lot of problems with my muffler bolts coming loose even with loctite on them. The loctite that we use on these machines fail at 149 degrees C. So to solve this problem I took the advice of one of the guys from here who said to drill the muffler right through on the threaded section and run a bolt through the hole and put a nyloc nut and spring washer on the other side and I havent had a problem since.

[Aussieheliguy]

Interesting, having the same problem with a OS50 std at our club. One of the guys tried honing the bore thinking it might be a glazing issue and it worked for a while, probably a couple of litres of fuel, but the motor has started playing up again. He is using Klotz oil.