I have never seen an engine get lean when theday gets hot. Normally if anything I have to lean it a bit. I bet he just isn't richening it enough in the first place. Tank position will not change how lean or rich the needle position is. It is only an issue when doing aerobatics. That is a tank that is too high will go lean when inverted and visa versa for a tank too low. But how lean or rich after adjusting the needle only depands on how you set the needle.

I'm inclined to agree with Earlwb.  Try richening up the high speed needle a 1/4 turn and see what happens.  Good that there is some Castor in the mix to take care of those "potential" lean runs.

I would were I you up the oil content too.  All the old gurus here say use 20% total lubircant (oil).  That you can get away with 17% is your choice, that means a tad more performance but also a tad less lubiricant through the system.  Yes, I know some that even run 10 or 12% lubricant but at what risk?

Chip

Respectfully disagree there, SP. It's quite important, especially when there's little or no muffler pressure to help. I doubt it's the primary factor in the OP's case.

This likely has nothing to do with the problem, but you never know. I can see if someone leaves their fuel jug open a lot, that the voltatiles (methanol) would tend to evaporate faster than it would abosrt moister out of the air. so the old bad fuel would have less methanol in it and some additional water in it. so the percentages of the fuel components would be off then.
I just remembered that someone had run some tests on glow fuel contaminated with different percentages of water. He had some information about the effects of temperature on it too. if I remember he could run the fuel with a considerable amount of water in the fuel, up to a certain point though.
They were discussing in this thread here about glow fuel with upwards of 3% water in it would still work Ok. Someone claimed to have run 20% water in their glow fuel, but it didn't make sense to me at the time.
http://www.rcuniverse.com/forum/m_12...tm.htm#1306444

How about asking someone else at the field for a tank of "his" fuel for the 2nd flight. If it flies well, make sure your mate flies with his "new found mate" and trade fuel.

Or - buy a new gallon of premix.

at least you got it!
what's funny is all the guessing that's been going on.....................

I have had inverted engines so low the fuel would run through the carb. I would clamp the fuel line with a hemostat prime the engine, start it and take the hemistat off. I had to turn the needle down a bit and the idle was a bit tricky, but as long as I did not fly inverted it ran fine. I have also seen tanks set real low, as long as you have muffler pressure,especially at idle you can get it to run. In fact one poster here has had tanks mounted about 6 inch's below the engine on an air boat and he was able to get it to run, though Ithought it would be an issue that low.

I'm the guy with the above mentioned airboat. With the fuel tank 6" below and 1" behind the carb, the engine would draw fine. Farther away than that and you might have draw problems. On my boat, the engine ended up being 2" further behind the engine causing some draw problems. I had to run the idle needle a bit richer which required glow left on. I bought a pump to try.

I think the OP's problem is either bad fuel or mixture related. My inverted engine was getting too much fuel because of the over rich idle needle b

A tank that low might work in a boat, but would probably be problematical in an airplane if you flew any aerobatics at all.

Heli's have the same issues with tank location, and run header tanks to keep the engine reliable. As I said before, I doubt tank location is a factor in all 4 different birds.

I have never seen a heli that didn't have its tank mounted at least close to being centered, yet they usually have header tanks. Maybe a few scale heli's but I don'tthink I have seen a serious scale heli model for a very long time. Even so a header tank will not correct an off center tank, just as raising a fuel line well above or well below the engine will not affect the pressure. The header tank is there to keep a full tank so that very aggressive aerobatics will not cause the engine to pick up air and foamed fuel.

That is my point.

G'day Digger,

I have seen the issue of excess oil from the muffler stop an engine on the second or third flight. In this case it was an older OS 46 SF. The muffler nipple was flush with the inside of the muffler and was allowing raw oil to travel to the tank. It took us months to work it out, but eventually we mounted the engine and tank on a stand. When we ran it we could see the raw oil droplets accumulate on the bottom of the tank. Eventually the clunk would pick up a slug of raw oil and the engine would die.

The fix was to fit a longer nipple.

I remember Brian Winch mentioning a similar problem in Airborne Mag. Turned out to be a home made rubber or similar exhaust extension. The extension would be fine for the first flight but would heat soak and slowly soften. By the second flight it would collapse and either strangle the engine or change the pressure to the tank enough for the engine to die. Of course by the next weekend it regained its strength and the process would be repeated.

Can't quite see how this would affect all your friends engines but hope this is some help

Good luck

Dave H

Same happened to me once... after some time the engine just stopped with any logica explanation. Solution; closed the "normal" pressurisation point and placed in antoher upper place. Then OK.
Cheers

In our case the engine was canted over to the right so the nipple was already at the very top of the muffler. Problem was the nipple being flush to the inside of the muffler.

But you make an excellent point.

To the OP are any of the muffler nipples at the bottom of the mufflers?

Well gents, the weekend has been and gone, and it's happened again, this time with MY tuning and me flying.

The aircraft has an inverted ASP 61 2/C

First flight, no problems (aircraft was set too lean for my liking and richened up.) The engine never missed a beat, and I felt confident enough to hang it from the prop for some time.

Second flight (in the space of 10 minutes) was a disaster. Start engine, wander out, rev up take off, and a flameout at about 25'. I ended dinging his plane getting back on the ground (stupid clump of reedy grass staved in the LE!)

I'm confused.

One thing that I did note, was that the muffler pressure point is nearing the bottom of the muffler, it's up on one side, by about 1/8" from the bottom. That said I've run inverted 60's before with exactly the same setup and not has this problem.

The mystery continues.

Change the pressure point to a higher position. Usually, oil (from the first flight) blocks the pass through and tanks does not receive pressure on further flights... I'd had the same problem once and solved this way.
hope it helps
Guille

then try your engine in his plane..................still sounds a bit strange to get one full flight and then nada on consecutive flights.

i have pressure fittings in the same location and never had any problems like this.

Another weekend, another conundrum it seems.

This time we were flying with two indentical aircraft with different engines, but essentially the same fuel (18% oil (roughly 3% castor) and no nitro.

I was fighting the dreaded NVA bubbles on 'new' 46fx and he was having lean runs with his Enya 40 ss. I should also point out that it was around 10°c and dry.

After a while I suggested he borrow some fuel from a friend (local store bought stuff, I'd say 10% nitro and probably straight klotz from the colour)
he got a nice COOL run with his enya and a much happier engine all round.

This seems a bit counter intuitive to me, I would have thought that 10% would have overcompressed the enya and made it run hot/like a dog. Turns out the opposite is true.

IT then begs the question, is the addition of small amounts, 5% or so of nitro a way of cooling the engine and allowing more fuel to pass through the motor, without adversely affecting the C/R and timing?

The only engines i've stayed away from Nitro are Moki's and Lasers. Everythig else has 15%, both 2 and 4 stroke except the YS's that drink the bank bustin' 30%. I experimented some years ago with an OS 1.20 Surpass on 0-5-10-15-20 and 30%. No questions, nitro helps all round running, tunning, response... the list just goes on. Engines just benefit, they're just happier! And if the engine happy, so is the pilot. Having said that... 5%-10% what's the point? You're getting some benefit, but not max benefit. 15% was absolutely the optimal place for me for sports engines. The most cost effective, max response deal. But the two strokes on 15% do seriously benefit from one extra head shim. Drop down to 10% and the shim isn't necessary but you loose out on response and stability. 15% and Enya 3 or F plug (specially in inverted 2 strokes) plus 15%... Shorts out 98% of all troubled engines.For some reason, people believe that nitro is all about adding extra power. Nothing could be further from the thruth IMO. The engine can only deliver what it's designed to deliver... and it'll never realize that unless you run it the way the manufacturers do. That means 15%.

Sounds like water in the fuel to me. I'd ditch it.  []

when i read that higher nitro improved things i have to ask...........what size props are being used on the engines.

our YS 4 strokes act like this when overloaded, but then run better with higher nitro.

Does seem that way, but actually the extra nitro needs more air to burn, hence a cooler running engine (all else being equal). Heli guys recognized this early on, as do the speed guys. 30% is cubic $ tho!  [X(]

Enya 40 ss - prop 10x6. The same prop we've been running on 40's since the 70s. I've had a stack of enyas in my time and none have been upset at using FAI fuel until now.

OS 46 FX prop 11 x 6. These engines are relatively lightly loaded, which does not account for the excessive heat.

man that is a stumper..............are you going to try fresh fuel, plug and all?

your engines are running fine though right?