After a long lay-off, I finally got around to test-running my LMH's engine this weekend. It's the 110 model heli and I got it second-hand BTW

I flushed the tank and engine through with fuel, removed the needle and washed that out too, before attempting to start-up. No problems with starting at all

Running at full bore I tweaked the needle until it was running just a little rich - loads of power, nice! Dropping to tick-over the engine ran very smooth and the pick-up was quick and reliable. I thought I was almost there, but unfortunately not

Keeping the throttle around three-quartes open, as if hovering (but with the heli clamped down), the engine suddenly stopped. I increased the number of washers until I had five in there. The throttle response and tick-over were still ok, whilst the starting was just a little more hit-and-miss. But still the engine stops dead after a minute or two at a high throttle setting

The engine seemed really hot, but turning the needle-valve out caused immediate four-stroking

Fuel: I've read that I'll need 30% to 35% nitro, but I haven't got any of that right now. Looking on the 'net I came across someone saying he runs his LMH on 15% successfully - but I din't have any of that either - but I did have some 10% to hand, and that's what I used

I thought that the lack of nitro would just mean I'd have less power available, but I'd be able to check-out the engine's general reliability. But could it be that the engine needs the high nitro just to keep it running?

Any advice would be most welcome

Tony

I've never tried 30 or 35%, but I've been using Wildcat 20% in my LMH 110 with great success. I've got 3 washers in the head and the engine never misses a beat. It did take a while to get the needle just right, but I haven't had to adjust it since. You may need to remove a few washers if you're running 10 or 15%. You might want to try a different glow plug as well.

Ben

Thanks for that Ben. Good to know the engine works well on 20%. I should have mentioned that I did try a couple of plugs just to make sure that wasn't causing the problem, and it wasn't

Just a thought, it's not very warm where I am at the moment, around 16C. Do you think a higher nitro content is needed in colder climes (I'm making an assumption that it's a fair bit warmer where you are)

Tony

I don't know whether higher nitro could be considered a requirement for cold weather flying? I don't think it should matter. I flew mine a few weeks ago when it was about 45F and last week at about 65F, ran fine both days (I don't remember having to make any adjustments either).

I've also ran Coolpower 15% with no problems. Heli still flies great, not that I do anything too exiting with it.

Ben

FWIW: My LMH 110 wouldn't run worth a flip with no CASTOR OIL. You didn't mention what brand of fuel you're using, but if it's pure synthetic, you'll never get the engine to run properly. I used Cool Power Pro Pattern 20/20 in mine with 4oz of Klotz Castor Oil per 16oz (I had a separate bottle that I kept and mixed it in).

Also, it has to be RICH. Mine was slobbering rich with raw fuel dripping from the exhaust as it flew. If I leaned it out any more, it would die. Power was good and it never quit on me as long as I kept it rich.

I have always had better luck in cooler weather, regardless of fuel. I have run on 20%, 25%, and 30% and all worked well. I run 30% simple because that is what I have and it gives me a few extra rpm at the head. I do not think you will have any trouble in the cool weather, but you might want to pick up some higher nitro fuel. I have had excellent luck with the Norvel 25% mix, but it is incredibly expensive (12$ per quart!). If you would like to rule out fuel trouble for sure, I would get a new quart of this and get the engine running right. You can always switch to another fuel later.

If I had to guess from your description and my limited experience, I would say you are overheating. When I run through a full tank at high throttle settings the engine becomes hot, but not fuel sizzling hot. You should be able to grab the heat sink for a few seconds after a run and not burn yourself, but it will always be too hot to hang onto. When my engine overheats due to some problem or poor setting on my part, it runs well for perhaps 30 seconds to a minute and then will die despite needle valve settings.

A couple of things to check:

-Cylinder head leak: Make sure the glow plug, glow plug seat on the engine, and the glow plug seat on the heat sink are all meticulously clean. If you get a small piece of dirt or hair or whatever in there it will not seal properly and this always causes overheating. Also make sure the heat sink is screwed on as tight as you can manage. I hold the crutch in one hand and the heat sink wrapped in a cloth towel in my other. Seeing as how it is nearly impossible to hold the whole thing, I don’t think you will ever have any trouble with over tightening or possible thread stripping.

-Crank case back plate leak: I have had this loosen up on me a couple of times. If loose the engine will never run right, and most likely will go mysteriously lean as it sucks in extra air. Take the engine off the crutch and crank that down for all you are worth. Again it is so difficult to actually put any kind of tool on this part I don’t think you will ever have to worry about stripping the treads. I use a small screwdriver whose shaft will lay across both of the small notches in the back plate. Just don’t screw up the notches J

-Loose carb: This has never happened to me, but also is supposed to throw the mixture off and cause all sorts of engine problems. The old ones (like mine) were just glued in! I would not know how to check for this other than seeing if the carb wiggles or rotates. If so, best of luck fixing that I hear its pretty tough.

-Damaged needle: Take the needle all of the way out and take a close look at the tapered section. If there is a small ring, groove, notch, step, ect. somewhere on the taper I would throw the needle out and get a new one. Often the needles are over tightened and the needle seat will gouge a small groove or flat into the needle. This makes it about impossible to ever set the needle valve correctly again. Adjustments in the range of the flat spot do almost nothing. Turning the needle in past the flat causes the engine to be much too lean while backing the needle out past the flat makes everything much to rich. A new needle is defiantly worth the few dollars they cost in this case. I find the engine runs well over a very broad needle setting with a good needle.

-Air leak around needle threads: I have seen small bubbles where the needle threads into its seat on my engine. Litemachines said the engine may be pulling air past the treads of the needle valve into the carb. They suggested cutting a small piece of fuel tubing just the right length, slipping over the needle and then screwing the needle back into the carb. When cut to the right size the tubing should tightly seal over the needle itself as well as the threads sticking out of the carb.



Give that a go and see what you think or find out. As far as mixture goes I would recommend running as rich as possible while still getting good performance. This little engine always seems to have over heating issues, so I try to keep things nice and rich. I run this engine much further from the optimum lean point than I did my Cox 0.49’s from the days of yore. Each new day I fly I start the engine and then hold a tach under the blades. I set the needle as rich as I can while still getting 2000 rpm at the head when wide open.

For what it is worth,
Spiro

Wow! So much response - I'm really grateful to you guys. And I guess I need to tackle each suggestiong in turn to make sure I haven't missed-out on anything

1) Ben, I take on-board what you said, and you're probably right. Guess I'm making the mistake of "looking for a reason" to pin my engine's behaviour on, rather than looking to cure the fault. Good to know you can fly on 15% too - high nitro seems expensive where I am (this is taken from an e-mailed response to my local model shop in response to my enquiry about high nitro fuel: We stock Cool Power 30% Nitro fuel @ £26.99 in a US Gallon or an Imp Gallon of Duraglo 25% @ £21.29). And of course, my thinking this is expensive could be a clue as to why I'm having problems. The fuel I used for my weekend test-runs works fine in my fixed wing models, but it was very cheap!

2) Bimmer, The 10% fuel I used is standard stuff, not synthetic, so that's not where my problem is. The actual brand is Southern Modelcrafts. And I take on-board that I need to run rich

3) Spiro . . . . plenty to check-out here! It's interesting that your engine has run better in cooler weather - so there's hope for mine here in the UK! I also see that you run 20% to 30% sucessfully. I'm not sure if I can buy the Norvel 25% where I am, but as you can see above, there are other options and the Cool Power 30%'s got to be worth a try (as you say, just to make sure that it's not a fuel problem)

Overheating is a possibility as I did find the crank case very hot to the touch after the engine stopped suddenly - I doubt I could have held onto the engine for a few seconds as I had that automatic reaction to withdraw my hand when I realised how hot it was. Your description of how meticulous the cleanliness needs to be is something I'll check-out the next time I try running the engine as I guess I may have been lacking in this area

The heatsink is on as tight as I could get it and the back-plate's ok too 'cause I checked that when I built the heli up. I haven't noticed the carb being loose, but it's on my check-list for next time. The needle is ok, in fact it looks perfect. Your explanation of how a needle which has been over-tightened can actually cause mixture problems is really good and I'll remember to look out for that in future! I've seen the air-leak around the needle threads in the past (not on this engine though) and know about the fix, but this one seems fine

Again, your recommendation to run the engine rich is noted (maybe I'm just running a little too lean as you're the second to mention that the engine likes to be set on the rich side)

I think my best bet is to go buy some of the Cool Power 30%, re-check the carb for fit, set the needle as rich as possible without cutting the power down enough to prevent lift-off . . . . and see what happens. It may be a couple of days before I can get to the model shop to get the fuel so feel free to mention anything else that comes to mind in the meantime

Many thanks for all your help

Tony

Funny how time passes-by so quickly . . . . I'd forgoten all about this post!

Spiro, You said: "Damaged needle: Take the needle all of the way out and take a close look at the tapered section. If there is a small ring, groove, notch, step, ect. somewhere on the taper I would throw the needle out and get a new one. Often the needles are over tightened and the needle seat will gouge a small groove or flat into the needle. This makes it about impossible to ever set the needle valve correctly again. Adjustments in the range of the flat spot do almost nothing. Turning the needle in past the flat causes the engine to be much too lean while backing the needle out past the flat makes everything much to rich. A new needle is defiantly worth the few dollars they cost in this case. I find the engine runs well over a very broad needle setting with a good needle."

You were "right on the money," my needle did have the "step" you so accurately diagnosed. I realised that there was a lot of excess "needle length," so I re-shaped it with some gentle filing and now it works perfect! If only I had taken the trouble to find my reading spex when I checked the needle the first time!" [&:]

Many thanks for this

Tony