Hey Bros,
Got a ? I am now having a problem with my viper, the engine actually.
I get her up in the air and put the power to her and in a few seconds she dies.
The engine is a os 40 fx with a 9-6 apc. she turns on the ground 16 k, it also has a macs muffler
Im running 15% fuel and the fuel is new. This is the fuel I always ran with no previous problem.
To lean?
If Im getting 16.5k on the ground should I richen her up to around 15k?
Scratching my head on this one.
Tank is good no leaks, screws are tight on engine.
Any help or suggestion would be appreciated.

In addition, should I be proping her more..say a 9-7or 8 or 9?

thanks,
mike

I would richen it up quite a bit, and try it again....just to rule out overheating.
I would try a 9-7 as well....more pitch.

Dave.
Revver Bro #4

Will do.
Think I will try a 9-7 and 8 see what that will do.
How many rpms will I gain in the air do you think?
Well, im going to drop her down to 15k and play.
Pic coming tomorrow..hopefully.

thanks,
mike

That sounds good....just take it easy at first till you get the engine sorted out.
How much running time do you have on the engine ? Are you using fuel with
castor ?

Dave.

Wow,
Dont know how much time but its been with me for a couple of years at least.
I dont think my fuel has castor in it. It may but im not sure. Could I add some castor?
Ill ask Mike McMurtry the hobby shop owner he will know for sure.

Thanks,
Mike A

You should have some castor in your fuel. That engine has a nickel liner in it
and they are weak, it needs all the help it can get. It will run much cooler with
castor in it as well. PowerMaster is a real good fuel, it has 1/3 castor oil in it.

Jett Engines manufacturing recommends PowerMaster. You can get some good
castor at a motorcycle shop. I add some to break-in a new engine, in the nickel
liner OS Engines, and some extra in the four strokes as well.

Dave.

You should normally set the engine about 800 rpm down from peak prior to launch.

If it run ok on the ground and then STILL goes lean after launch, check the fuel system. You are very likely getting fuel foam. As the engine unloads in the air, it is hitting a note that is foaming the fuel.

Balance the prop

Make sure all of the fuel lines (including the tank clunk line) are intact and have no holes

Make sure the fuel tank is 100% wrapped in foam (can not touch anywhere on the airframe)
- or - switch to a bubble-free fuel tank

FBD, you might want to rephrase that a bit. I do think that Powermaster is not 33.3% oil. The 15% we use for racing is 18% oil. The oil content is 2/3 synthetic and 1/3 castor. So of the total oil content 12% of the fuel would be synthetic and 6% of the fuel castor,

Ed S

Ed, Must you always rain on everybody's parades and point out your supremacy to us mere mortals?
GS

Gary, Gary, Gary, Read my post. I said that the fuel we use is 18% oil.

You are definitely a supreme smartass, you succesfully outsmarted yourself!!

Ed (Smartass) S

Hey Gary,

You cheated, no editing allowed!

Ed S

I would stick with the 9x6 with a .40. The 9x7 sport prop will be a little too heavy (we don't even use them on .46 FX's racing). You may want to play with some of the lighter pylon props:

8.75 x 8.5W
8.75 x 8.75 W
9 1/2 x 7 N (This is actually lighter than a 9x7 sport prop)

My guess is your either getting fuel foaming or an air leak in the fuel system. This engine should have no problem running in the 16-17K range.

All great suggestions, thanks bros.
Redid the tank today and is surrounded by foam cushion.
Lines redone as well, no holes.
Put the 9-7 on it and richened her a lot when run.
On the first few attempts at high rpm she died and I richened her up lots.
Finally got a full blast run with rich setting, sounds like thats the trick, just too lean...doh!
Hopefully will fly her tomorrow.
Also, those GP racing wheels suck...goodbye....found a couple of lite sponge wheels and tricked it out, cut the fat wheels in half and vola! lighter wheels. You will see it in the pic momentarily.
Thanks bros for all your help.

Mike

Yes, Ed....you are correct. 1/3 of the oil content is of the castor....

...but then....you, and I, and everyone else knew that.

FBD.

Heres the pic...I hope I do this right.

And the home made wheel...(one regular sponge wheel cut in half)

Set the high speed needle with the nose of the model straight up. You should be able to pinch the fuel line and hear an RPM jump. You should creep up gradually on the correct setting from the rich end. While airborne, shut the engine down at the slightest hint of sagging and re-needle it. One of those JETT tanks would be money well spent. If your engine doesn't hold a compression seal for 5 seconds while cold at TDC, then you have already cooked it. The APC 9x6 is the workin' prop with that engine.

Ill definitely check that....got great compression.
I played with the engine yesterday and ran it really rich. Seems to be fine now.

thanks,
mike

Another possible source for high rev flame out is glow plug. Recently, I had a OS #8 plug replaced in my F20 that solved the problem with high revs flame out in the air. My theory is that the plug coil separates with heat expansion at high revs, and cause loss of glow. My motor was running slightly rich and still flames out at high revs until the plug was replaced. And it was not an old plug either.[:-]

The only glow plug failure that will stop your engine is when the plug wire separates from the plug body and flies out the exhaust (and messing up your engine in the process ). The coil does not have to be intact for the plug to be working. You will only notice the plug is gone the next time you try to light it with your glow starter. Once the engine is running, the plug stays lit, wire broken or not.
I have even lost part of the coil at one time, but there was still enough of it left to keep the engine running, although it ran crappy of course.

and they call me cheap !.........

My 46FX wasn't a stroll in the park as far as breaking it in, but once it was I didn't have to touch the needle since. I suspect you need more time with rich to lean , lean to rich running.

PS not the same engine ? , I know ........

Well, I have so many damn parts laying around I figured what the hell right?
The engine is plenty broke in...Im just an idiot and didnt richen it up enough. DOH!
Pretty sure Ive gotten it straight now.
Thanks all.
Mike

Mike....it wouldn't hurt that engine to add a couple more ozs. of castor to
the gallon and bump the oil content to 20%. That nickel liner needs all the help
it can get.

Dave.

Will do FBD thanks for your help. Oh by the way how can I get a t-shirt or stickers?