LA.46 can't get a setting

I've been having a nasty time with my LA.46. Any setting I have on the ground will change as soon as I get in the air. If I set it a tiny bit slow on the ground, it gets slower in the air. If I turn in the needle to get, maybe 500 more revs on the ground, it goes dead lean in the air. I started with a wedge uniflow and tried muffler pressure and no pressure, also uncovered the overflow so it would work like a skin vent. I tried a round plastic uniflow, pressure and not, also a rectangular plastic with uniflow. I tried a .285 and .265 venturi. Props 11 x 4, 12 x 4 and 6, 11.5 x 4. Added a total of 3 pop can shims, checked for leaks everywhere. Fuel is 10%meth. half and half 20% oil. The closest I came to an OK run was with a Master Air Screw 12 x 6 and the rectangular plastic tank uniflow with no muffler pressure, but still wanted to run away.
Someone mentioned in an earlier discussion that the secret was 25% oil which I haven't tried yet--can anyone suggest something that I didn't check??

Have you tried a new glow plug? Sometimes the element can age in such a way that it can't support a nice rich run. Since you seem to have covered all bases with respect to tanks I'd try try this.

Hope it helps.

How much time did you run it in on the bench? How did you do it? It could be that it just needs more run in time.

More run time? Possible. And there is always the obvious, but sometimes forgotten, "junk in the needle". If you haven't checked, take out the needle valve and check to see that everything is clean. Blow it out and shoot a little fuel through it backwards. Then reinsert the needle and try again.

Also, is the hole in the spray bar aimed correctly (somewhere in the "down" direction)? Are you using a rear or front needle? An OS or a "something else"?

The motor has about 90 minutes on it.
Fireball hot plug, I changed it about 4 runs ago, no change.
The ST needle was the first thing I checked, it's clean.

Aaaaaaaaah!

Here's another guess.
Is it possible that you are getting fuel foaming? If your fuse has a resonance at the higher rpm, then after launch the engine rpm increases, possibly putting you in the bad rpm range. Then if it starts to foam, it will go dead lean. Setting the needle "too rich" never lets the engine get into the resonance range, but also doesn't give you the flight you want either.

If you haven't already tried it, add a small amount (just a spritz) of Armorall into your fuel. That should stop any foaming.

make sure that "spritz" is aimed in a gallon can. A spritz in a 4-ounce fuel tank would be waaayy too much.

90min. Should be plenty on that style of motor. You said 10% meth.??? Did you mean nitro????(nitormethane)

You also said that you would change it 500 rpms on the ground. that sounds like alot. Maybe just try a 100 up at a time.

I set my 46 to just be in a beeping 4s. You know kind of back and forth between the 2 and the 4.(9000) I run a 12.25X3.75 apc. The length of the 12 6 gave you enough load to keep it in check. Still it sounds like something is a miss.

You said plastic uniflow. I run the plastic Sullivan clunk tank setup just like the RC application with the extra vent line added for fueling. I pressure the vent line. They show on the instructions how to set it up and it works well. I have also had very good luck with a uniflow tank(the only time I have ever had luck with one by the way) on uniflow I pressure the uniflow line so I guess it isnt uniflow. I do this because it gets better milage and I can get through the pattern without a runout. I think the plastic one will work fine for you. Make sure the pickup is inline with the needle. Remember the clunk slides up as the plane flies. The clunk sits in a straight line with the brass tube it is attached to. So where the brass tube exits the tanks is where you should set it up even with the needle.

Also Len brings up a good point about the hole in the spraybar. Make sure it is pointing down or a little down and forward would be best.

How did it run on the bench? Would it needle well? Could you pinch the fuel line and have it go lean and come right back? Did you break it in fast or sloppy rich or in the middle? A little fast with an occansional 4s works well for OS engines. They have a medium taper and they seat nice and quick.

If it needles fine on the ground and then in the air goes to the crapper. You might have a bad gallon of fuel. I fought one for an entire day(9 flights) then someone said here try my fuel and WHAM it was working great. I had some of the same stuff you are having. Unpreditable runs and junk like that.

>The motor has about 90 minutes
>on it. Fireball hot plug, I changed
>it about 4 runs ago, no change.
>The ST needle was the first
>thing I checked, it's clean.
>
>
>Aaaaaaaaah!

ST needle valve. Now we are getting somewhere. The .265 venturi is way too small for the ST needle. (This is a good size for the .40 with an OS needle). Even the .285 is too small with an ST needle and the .46. I would go to at least a .297 or .301. You can go as high as a .312 or even .316 with the boost port blocked and everything else right.

Also, make sure there is no leaking around the venturi o-ring. Sometimes when people bore the cross hole for the larger needle, things get a little off. You should have to compress the o-ring by pushing down on the venturi when inserting the needle. If it just slides in without any "juggling" you are probably sucking air around the venturi.

Thanks. I'll try a larger venturi--if the wind ever stops blowing, and let you know?
I noticed that the motor wasn't very responsive to the needle--could this be the effect of too small venturi?

>
>I noticed that the motor wasn't
>very responsive to the needle--could
>this be the effect of
>too small venturi?

Yup. Can't breathe

If all this fails, I would try more oil in the fuel, I had this same problem, using 20% half syn/half castor and tried everything. Went to 25% sig castor and it was like a different engine.

>I've been having a nasty time
>with my LA.46. Any
>setting I have on the
>ground will change as soon
> as I get in
>the air. If I set
>it a tiny bit slow
>on the ground, it gets
>slower in the air.
>If I turn in the
>needle to get, maybe 500
>more revs on the ground,
>it goes dead lean in
>the air. I started
>with a wedge uniflow and
>tried muffler pressure and no
>pressure, also uncovered the overflow
>so it would work like
>a skin vent. I
>tried a round plastic uniflow,
>pressure and not, also a
>rectangular plastic with uniflow.
>I tried a .285 and
>.265 venturi. Props 11
>x 4, 12 x 4
>and 6, 11.5 x 4.
> Added a total of
>3 pop can shims, checked
>for leaks everywhere. Fuel
>is 10%meth. half and half
>20% oil. The closest
>I came to an OK
>run was with a Master
>Air Screw 12 x 6
> and the rectangular plastic
>tank uniflow with no muffler
>pressure, but still wanted to
>run away.
> Someone mentioned in an
>earlier discussion that the secret
>was 25% oil which I
>haven't tried yet--can anyone suggest
>something that I didn't check??
>

Put a mac's muffler on it and run it at 10,300 on the ground and have fun.10%nitro 25%Castor 11.5x4 apc Prop

So here's my questions>>>>>Is your plane a profile? What tank r u running now? How far from the engine is it? What size fuel tubing are u useing? How old is your fuel? How many head gaskets?

Scott(got to know) Riese

A friend of mine had the same problem with a different engine (HP40, I think). I gave him a tank of my stunt fuel (around 25% oil) and his touchy needle settings went away. Amen to more oil.

I'm having a great time with the LA .46. I'm using an ST NVA, One of Leonard's .281 venturis, three head gaskets, ThunderBolt 4-cycle plug (a notion provided to me by the late GMA), Powermaster 10% nitro(GMA Blend), 22% oil (50/50), one once of Randy's Aero Oil per gallon, and a Stalker 11-6 carbon three-blade prop.

It leaves the ground at 9350 rpm in a two stroke, makes one lap at that spedd and then settles into an awesome 2-4 break. The muffler is Big Art's (Double Star) on muffler pressure. I hope this helps....

CML

There is no boost port in this motor.

>A friend of mine had the
>same problem with a different
>engine (HP40, I think).
>I gave him a tank
>of my stunt fuel (around
>25% oil) and his touchy
>needle settings went away.
>Amen to more oil.
>
>Fred

NOT THE SAME ANIMAL>>>>>>>>>>>

Two many head gaskets..........Not producing the power that the 46 will put out. The LA-46 is made to run over 10000 rpm's anything less....is a bowl of rice.

scott( sorry had to do it) Riese

Make sure the collet on the needle valve is tight enough. The needle should require some effort to turn. If it's too loose the tip of the needle will vibrate and make for the inconsistency you're experiencing.

Ted

p.s. If this tip solves your problem thank Big Jim Greenaway who saved me a very distressing nats with ST .46s many years ago.

I just had to stick up for my big brother(Cleon). He speaks of my over 50oz. Foam G-Nobler. I spent a season on 57 foot lines with a DS 40 to no avail. After watching Walter Hicks fly a wonderful Imitation (Chipmunk) at last year's Ted Goyet I tried the LA 46, three head gaskets and a Stalker 11x6 three blade. I'm now on 67 foot lines and 5.2 to 5.3 laps. I too had a loose collet. I leave the gound at 9350. It pulls not unlike one of Leonard's FP 35's which I used to learn on my 55oz Twister. It may not have all the power available but on an off day I can fly the entire pattern all four cycle. It sounds like a ST-60. I would compare my runs with any blue-printed ST-46. Bob English flies my GMA ST-46 in his Rabe Mustang. A couple of weeks ago he watched my plane and nearly fell out of his chair. If you want a world class 2-4 motor with plenty of power, three head gaskets and load it with prop.

Lewis (just my opinion) Lingwood

My two cents: Is it mounted on a profile? Some times a loose front end can give you headaches and engine runs simular to what your decribing. I love my LA46! I use old recycled 12x6 TopFlite Power Props cut down to 11.5x6, two gaskets, .285 venturi, W/ST needle, 22% oil, 2-4-2-4-2-4-2-4-4-2-4
Mark Boesen

Does your LA have a plastic cranckcase-backcover? If so, have you checked the air-tightness. We had similar problems like you described with 15 and 25 LA s, because of this. Seems the fit wasn't all that good. Using some plastic goo gasketstuff cured the problems. Also the coarse (we Continental-Europeans are used to M3)thread on the screws doesn't look too reliable... But that can't be changed easily.

UPDATE!
For last weekend's contest I switched engines to a TT.42, which worked out fine--so the trouble maybe isn't the plane (a profile) or tank. I mentioned my problems to Jeff Higgs (good engine man) and he thought that maybe my 3 pop can shims could be leaking, and took the engine,removed the extra shims, and domed out the head, reducing the squish band and comp ratio to 8.6/1. I ran the thing last night and it's absolutely great. I launch it very wet and it comes in a bit in the air, and a whole lot vertical.
Funny thing--the TT.42 can barely do the pattern with the 4 oz.tank in the plane, while the .46 does about 15 laps at the end on the same tank, and the plane seems to have more oomph with the 46. I'm looking forward to flying it at Brodak's.

LAST EDITED ON Jun-06-02 AT 08:41 AM (CST)

>I ran the thing last
>night and it's absolutely
>great. I launch it
>very wet and it comes
>in a bit in the
>air, and a whole lot
>vertical.
>Funny thing--the TT.42 can barely do
>the pattern with the 4
>oz.tank in the plane, while
>the .46 does about 15
>laps at the end on
>the same tank, and the
>plane seems to have more
>oomph with the 46.
>I'm looking forward to flying
>it at Brodak's.

Jim;

Interesting.

Just to look at the numbers, what would be some of the differences between the setup of the two engines? Is the TT 42 running with the boost port blocked? (We know that the LA 46 comes without a boost port). What are the sizes of the venturis? More appropriately, after taking into consideration the NVA, what is the effective choke size?

>
>Interesting.
>
>Just to look at the numbers,
>what would be some of the
>differences between the setup
>of the two engines? Is the
>TT 42 running with the boost
>port blocked? (We know that the
>LA 46 comes without a boost port).
>What are the sizes of the venturis?
>More appropriately, after taking into
>consideration the NVA, what is
>the effective choke size?
>
>Regards - Bob Kruger

I would be interested in this, too. The TT .42, although outwardly it looks a bit like an FP copy, is a different engine altogether inside. Different bore, stroke. No parts interchangeability. The LA, on the other hand, is the same bore/stroke as the FP (The LA 40 compared to the FP 40). Just uses a different piston, cylinder (thinner liner). The LA even uses the same crankshaft (now cast instead of fully machined out of bar stock) as the FP as well as the con rod and venturi. And so does the 46. Same shaft, con rod, venturi as the 35/40 FP. This may account for some of the "friendliness" of the engine (with a loss of power) as it is very much choked down. It could also explain better fuel mileage is you are having to run it leaner. The LA, if it is using the stock venturi, is using a .265 venturi with a .135 spray bar. What is the setup on your .42, out of curiosity?

Sorry for the late reply, I've been away. The TT has a .280 venturi with a ST needle. I've blocked the boost port, no extra gaskets, running an 11.5 x 4 APC. Seems to be a very strong engine with a real funny quirk. If I try to come close to the in-air rpm on the ground, it'll go dead lean after the first lap, but if I let it go slobbering rich, it comes in real nice. I've had to find this launch setting by tweaking in the needle a bit at a time BEFORE I start the engine. Sometimes it almost doesn't want to stay running and I have to hold my hand over the cylinder to let it warm up. If I turn in the needle to lean it out a bit on the ground it goes totally wonky in the air.

Well, our next question is deck height. Every mass produced engine manufacturer builds in tolerances, and if deck height isn't factored into the equation, we get lots of differences. I shoot to correct deck height first of all. You can then drop the cylinder some (again need to correct compression) and can modify the head chamber (wide squish band on stock engine)

The venturi you are using is too small for this engine, even if it were stock, if you are using the ST needle. I will typically go to a .297 or even .301 venturi on these engines with an ST needle, blocked boost port, and other modifications.

Do that, and then compare it with the stock LA 46.

First things to look at would be the backplate seal (plastic backplates should have an "O" ring, IMHO), venturi seal and NVA for clogging or hole location problems. I just started running an LA .46 last Saturday, and it's great (with Tower .40 backplate). The one thing I'm not too sure of is the RSM ST-clone NVA. It won't shut off completely, and when it was in a Magnum XL .25, it ran ok...fully closed. I thought it might be better with the bigger engine, but it's still nearly closed, limited by the threads on the NV. I have some more of these, and will try another one, but for now, I'm not impressed with the NVA. Also think my venturi is on the small side (.285") with the Bruline fine filter, but I need the filter. When the engine run time stabalizes, I'll see what my fuel consumption is and increase the bore if I can. Steve