View Full Version : Holed Piston on Second Gallon!
nikpro
12-16-2007, 09:43 AM
Currently running the Align 50 engine and the first gallon went through superbly. I was using cool power 10%nitro. I ordered some more coolpower 10% Nitro from a different supplier and noticed that the rear plate on engine was hot after the first tank on this new fuel. I richened up from 11/4 turns to 11/2 turns for the second tank but whilst hovering I heard a 'pop' and the engine died; fortunately I was very low to ground.
Anyway after an examination I now have a lovely hole in the piston!
There were no air leaks and no fuel blockages - why should a fuel from the same manuacturer run so differently?
http://i184.photobucket.com/albums/x184/nikpro/IMAGE_008.jpg
captcasper7
12-16-2007, 11:14 AM
I had the same problem many years ago when a Thunder Tigher 50 did the very same, seems the head bolts worked loose and the engine leaned out and pop, hole in the piston.
I guess some how your engine leaned out
aevans692
12-16-2007, 11:25 AM
10% nitro.. I dont think you should de using that anyway ..
that seems a bit low on the nitro front you should go with at least 15% and that's not brilliant , if you can go with 20% is better bang for your money your heli will fly loads better.. and 30% for best...
10% seems a bit low even for learning with..
Sorry to hear about your engine, I don't think a new piston is too expensive, don't forget to run it in again.
I had a head on my os 50 hyper come loose, as mentioned early on , I never checked the head screws from the box, I was lucky no damage was done, since then I check them before fitting and tighten them down with a bit of thread lock..
TMoore
12-16-2007, 12:06 PM
What is shown in the picture is what is known as a lean run. What you will learn is that anytime you change fuel manufacturers, it is always best to richen up the needle. This is just the way it is.
TM
BarracudaHockey
12-16-2007, 01:29 PM
Were the head bolts loose when you inspected it? I've seen that a couple times but each time the head bolts werent checked during assembly and worked loose causing a lean run.
Also as TMoore said, different fuels require different tuning, nitro is only one part of the equation, if the oil percentage is different so will the methanol percentage and you need to retune.
nikpro
12-16-2007, 05:25 PM
headbolts were tight; fuel was from the same manufacturer - cool power; the only difference is one was 10% coolpower MV and the other was just 10% cool power!
It was significantly colder today - could that cause lean running as the air would be much denser?
I'm only new to hellicopters so this was done whilst just hovering the model and not under any real load,
The crankcase is badly marked where fragments of metal have got everywhere so it will be easier to buy a new engine as all the internals would need replacing.
matrix1171
12-17-2007, 12:55 AM
It was significantly colder today - could that cause lean running as the air would be much denser?
yes it can :thumbup:
Finless
12-17-2007, 01:51 AM
That as TMoore says is due to a lean run... I know you mgiht not buy it but I have seen that MANY times and every time just before it POPPED I was standing there saying "thats running too lean".
My .2 cents anyway.....
Bob
BarracudaHockey
12-17-2007, 11:43 AM
They have been known to replace them under warranty, atleast here in the US for that. The hyper piston is machined quite thin at the top where the older 50 pistons were not relieved in that area, a change they made, I assume, to improve balance.
darke
12-17-2007, 02:12 PM
i haven't used my hyper yet,so i guess i better go check the head bolts.bought the engine first haven't got the heli yet.......
BarracudaHockey
12-17-2007, 02:14 PM
Make sure the carb is straight and fully seated and snug it down.
Make sure the head bolts are snugged down.
Remove the backplate and look for any machining debris.
aevans692
12-17-2007, 03:20 PM
headbolts were tight; fuel was from the same manufacturer - cool power; the only difference is one was 10% coolpower MV and the other was just 10% cool power!
It was significantly colder today - could that cause lean running as the air would be much denser?
I'm only new to hellicopters so this was done whilst just hovering the model and not under any real load,
The crankcase is badly marked where fragments of metal have got everywhere so it will be easier to buy a new engine as all the internals would need replacing.
Sorry to hijack the thread , just wondering are you still running with the 821?
rototiller
12-17-2007, 05:18 PM
Make sure the carb is straight and fully seated and snug it down.
Make sure the head bolts are snugged down.
Remove the backplate and look for any machining debris.
+1
DK
nikpro
12-17-2007, 07:32 PM
Sorry to hijack the thread , just wondering are you still running with the 821?
No; changed to the Hitec's.
I understand it was running lean - just not sure why as it had been running very cool with the same needle valve setting on very similar fuel; I gues I must have got an air leak somewhere!
rototiller
12-17-2007, 08:36 PM
Low nitro fuel is kinda touchy on the needle. Hard to find the sweet spot somtimes. Plus I know my hyper didnt like 15%. With some 30% Nitro your needle gets very easy to tune. I think the 10% mixed with some cooler air, a new engine tuner and maybe a leak is what did the motor in ?
DK
The less nitro the more sensitive it is to the needle
If you changed from CoolPower (or CoolPower LV) to CoolPower MV the fuel mixture is thicker so to flow the same volume you need to open the needle and go richer
Practice doing knee high autos - if the engine makes the two stroke motor bike sound (ring ding ding ding) then you are lean - it's a very simple and effective tuning test
tungym
12-18-2007, 05:26 AM
Carbsmart may help you if lean needle is the only culpruit. We are too happy to 3D this devil heli. that makes us easy to push the engine limit and forget the importance of engine care and proper needle tunning. Change in ambient temp., humidity, wind does need needle adjustment.
I once blown my piston like you at 2nd galloon. My leaking fuel line suck air and lean the engine. The engine suddenly "bomb...." and lost all power after 6-7 tic toc.
Since then I install carbsmart and it saves my engine twice due to fuel tube fracture and another occasion due to fractured muffler pressure hose. Maybe now I learn to ground my bird immediately when I feel the power declines unexpectedly.