RL-53H Engine bogging between low and mid range

[satishkbg]

I am almost done with the breakin, only now did I start increasing the throttle, that I realize the engine bogs down. I mean the response is good from idle and increases as I throttle up and I see a good smoke, and then suddenly it bogs down somewhere before mid-stick completely.

My settings

High - at 3 turns open
Mixture valve - Flush with carb-body
Fuel - 10%NM
THRO-CURVE - 0-25-50-75-100
Hidden Needle - NOT TOUCHED

What I've noticed so far is that
- with Mixture valve flush: the throttle response is just ok, not really good
- with MV turned counter-clockwise i.e. opened, it gets worse, I mean no response at all to throttle inputs.
- with MV turned clockwise, i.e. closed into the body, the response is crisp. I see no smoke at idle, but as I throttle up, the smoke is good and increases with input, so does the rpm, but bogs down at just before midpoint at around 35-40% input.

I haven't played with the high-speed valve as I understand it comes inti play only after 70% of TH, but even any adjustment has not affected the issue i'm facing.

My MV is flush with body exactly at 12 'O clock and I turn it one-hour at a time, either way.

Can someone help me out to set this so that it transitions out correctly from low-mid to mid and mid to high and back. This is my first nitro heli.

Regards

[Fairview]

I have never run the engine that you have. I only have run OS engines. But generally speaking and I am assuming your mixture control is the low speed needle. I would set that to factory settings and leave it there. Are you sure the factory setting for the high speed needle is 3 turns? The OS motors generally run on the high speed needle 1.25 to 2 turns. A common misconception is that the low speed needle only affects the idle. It actually affects the mixture upto about 70% of the throttle throw. The high speed needle actually starts roughly at 30 to 40% of throttle throw. So between the 30% and 70% percent throttle throw both the high speed and the low speed needle work together. It is possible to be to lean on the low speed and to be rich on the high and vice versa. At least on the os 50 hyper(only 2 needles) you want a rich low speed needle so that the midrange doesn't lean out and then set the high speed needle where you want it. Here is a tuning video https://www.helifreak.com/showthread.php?t=276520 that really helped my out. This particular engine has 3 needles so just keep in mind that when he adjusts the 2nd and 3rd needle it is like adjusting your low speed(2nd) needle and your high speed(3rd) needle, and also with 2 needles the low one will need to be richer to keep the mid range from leaning out to much. Unless your really throwing the heli around your running most of the time on the mid range.

[satishkbg]

Thanks for the inputs - the approach is quite similar in most 2-3 needle nitro engines I guess. The RL-53's third needle is hidden inside the throttle-arm.

Anyway, I started allover from factory setting i.e. hidden needle at 1mm gap when barrel fully open (and LSN flush), LSN flush and HSN 3 turns out (and yes RL-53H recommended HSN is 3 turns out i.e. rich, and then you lean). I had to follow what most pilots recommended i.e. set the HSN for fully open throttle. Had to do it several times i.e. leaning while checking the back-plate temp. Finally the HSN was set to around 2.5 turns. The LSN actually settled quite quickly with just a little leaning - like you mentioned, it's almost at factory setting i.e. flush, leaned by about 1 hour. The HSN is finally about 2 1/4 turns out now, lot leaner. The transitions are smoother and mid is quite nicely responding.

Need to do further testing from here.

[Rob43]

Using stock RL53 carb?

[flyswatter40]

Hey Rob been runnig these for 4 years now, the lowspeed has a hole in the centre that the midrange needle goes into, this can get plugged over time by carbon in the fuel tank. Remove the main needle and the lowspeed needles. Take a clean piece of fuel line and press the end onto the hi speed needle valve inlet. Once on you can open throttle and blow threw the line then close the carb and continue, now remove that line and put it back on the intake nipple and blow threw it again while working the throttle open and closed there will be a difference in pressure. Once complete now pick up the low speed neelde you'll see it is hollow and there is a hole in the side of it, blow threw it both ways, once satisfied on the job reasemble the needles turn the hi speed in ti lit stops DO NOT OVER TIGHTEN, the open 2 3/4 turns out, put the low speed back in , you turn it in til it's flush with the side casing of the carb. Take the low speed now and turn it in a 1/16 of a turn and start your engine. You may have to turn the low speed an other 1/16 turn in or so and that'll have the low end tuned, now do punch outs in normal mode a few times then adjust the hi speed in a couple turns, once you have this set , you land and check the backplate you'll be able to count to 4 or 5 if it's tuned correctly. ENJOY there a power house. There is a midrange needle if this doesn't fix it, its under the throttle arm screw, it's very touchy though so do the other first, then if it isn't fixed and is still slightly lean carefully turn that mid needle just the slightest amount counterclockwise to richen it up a bit. That'll get her running right again.

[satishkbg]

Flyswatter40, thanks for those valuable experience sharing. I had to revisit this thread, as I was noticing there was still a slight hesitation during transition from 30-40. 0-20 has been rich enough but good response and smoke, 20-30 very nice, and just when I'm about to go into a hover there's a slight hesitation (kind of flat response) and then there the power coming in which stays up all the way up very nice. Before I play with LSN/HSN any further, I felt it would be nice to hear from someone experienced like you. Where do I focus?