dingo9882

Being that this Brison 2.4 is my first gasser I may sound crazy so here is some background on the engine and what plane it is in. I have it installed in a Kangke Waco. I am running 50:1 pure synthetic with a 20x8 Pro Zinger Prop. Lately though on the down lines at full throttle it has been making what sounds to me like a burbling sound. Now I just had this engine checked out by Bill Jenson, the gentleman that services them and its actually been running really good. Except for this burbling sound on the down lines at full throttle. Now at strait and level flight it flies perfect. Now the prop is spinning around 6,900 and 7,100 RPM. Could I be running the engine too lean or from what many many people have been telling me is its too rich on the high end? To be completely honest I am affraid to lean it out any more but I noticed that when the low speed needle is really rich it doesn't do this on the top end. But when I start to lean out the low end it starts doing this crazy thing only in the air on the Down lines. It seems to happen even at lower throttle settings. If I can I will post a video of it because it is hard to describe but if I can solve this problem this way it would be great.

JoeAirPort

My Feedback: (41)

Maybe the prop is unloading? Not sure why you'd want to go wide open in a down line. Normally if the engine changes mixture it's an air flow problem in the cowling (unless you have some other engine problem). Call the guy that serviced it and ask him.

dingo9882

It funny you say that because I was thinking the same thing but was not to sure about it. I have had a couple of people say it was unloading as well. Does this mean it is too lean or rich? or is this just the nature of the beast and it will not adversly affect the engine

tkg

My Feedback: (1)

So what. If it does not stop, don't sweat small stuff. Just fly it all year and break it in then worry about how it runs.
It takes 3-5 GALLONS of fuel to fully break in one of these chain saw engines. AND it takes 1000 hr to wear one out.

Don M.

My Feedback: (5)

I've had a Brison 2.4 for 10 years. Mine has always had a bit of a burble in the mid range but the only time it burbles at full throttle is when it is too RICH.

tlovett

My Feedback: (9)

I have had one of these for years (8-9). It just keeps going. I had the original CH ignition on it and that finally burned out........I replaced it with an RCExcel unit and it runs MUCH better than before. There are no burbles what so ever! It gained about 200 rpm and much more power.

I am a happy camper!