Andy Beetz
Jul 13, 2005, 05:11 AM
I recently fried one of these engines. At the time I couldn't understand
why, it always seemed to be running very rich. I did think it odd too though
that the most reliable setting 3/4 turns on the main needle was so far away
from the manufacturers default of 2.5 turns.
After many a shouting match, I gave up and paid the £25 to have the engine
repaired, which when it came back to me turned out to be a whole new engine.
I sought much information and instructions on what I should be doing with
the engine from the guy who replaced it.
I now have the new one running ok, well ok enough to allow me to run it in
without it asploding again. It's using half a tank (sceadu evo tank 480ml)
for 4 minutes of flight time. However, I had to lean the main needle to 1.5
turns to overcome the HUGE rich spot sat bang on 50% throttle, which the
engine will not throttle past if I go even one click richer on the main. I
am currently using standard mode for running in and have about a gallon left
to go berfore it should be done. I'm not using idle up at all at the moment
for fear of the lean top end.
From what I have learnt, I worked out why I blew the last one up. The rich
spot in the middle made me think that the engine was way too rich, and I
adjusted the main needle to get a nice linear throttle response, when in
fact it resulted in the top end being way too lean. It was pretending :(
This engine comes with a TNII carb. The instructions that come with it
covers all of the webra carbs. For the promix II carb it says this 'The
advantage of this principle over conventional twin-needle carburettors (TN
types) is that there is no tendency for the mixture to become excessively
rich in the mid-speed range'. However it does not warn about this rich spot
in the TNII instructions, nor does it inform how to eliminate it without
blowing the engine up.
The promix II has a regulating slot in the spray bar which I'm guessing acts
as a kind of mid-range needle. I have a spare OS32 carb (20C) doing nothing,
and noticed that it too has a regulating slot in the spray bar.
So I'm asking if anyone knows whether the OS32 carb will fit the webra
(without me removing engine from heli) without modification, the OS32 carb
has the same intake diameter as the current one. Also, if this would be a
wise decision or not, or whether I'm just not running the TNII carb
properly.
Thanks for any thoughts, guidance offered
Andy
why, it always seemed to be running very rich. I did think it odd too though
that the most reliable setting 3/4 turns on the main needle was so far away
from the manufacturers default of 2.5 turns.
After many a shouting match, I gave up and paid the £25 to have the engine
repaired, which when it came back to me turned out to be a whole new engine.
I sought much information and instructions on what I should be doing with
the engine from the guy who replaced it.
I now have the new one running ok, well ok enough to allow me to run it in
without it asploding again. It's using half a tank (sceadu evo tank 480ml)
for 4 minutes of flight time. However, I had to lean the main needle to 1.5
turns to overcome the HUGE rich spot sat bang on 50% throttle, which the
engine will not throttle past if I go even one click richer on the main. I
am currently using standard mode for running in and have about a gallon left
to go berfore it should be done. I'm not using idle up at all at the moment
for fear of the lean top end.
From what I have learnt, I worked out why I blew the last one up. The rich
spot in the middle made me think that the engine was way too rich, and I
adjusted the main needle to get a nice linear throttle response, when in
fact it resulted in the top end being way too lean. It was pretending :(
This engine comes with a TNII carb. The instructions that come with it
covers all of the webra carbs. For the promix II carb it says this 'The
advantage of this principle over conventional twin-needle carburettors (TN
types) is that there is no tendency for the mixture to become excessively
rich in the mid-speed range'. However it does not warn about this rich spot
in the TNII instructions, nor does it inform how to eliminate it without
blowing the engine up.
The promix II has a regulating slot in the spray bar which I'm guessing acts
as a kind of mid-range needle. I have a spare OS32 carb (20C) doing nothing,
and noticed that it too has a regulating slot in the spray bar.
So I'm asking if anyone knows whether the OS32 carb will fit the webra
(without me removing engine from heli) without modification, the OS32 carb
has the same intake diameter as the current one. Also, if this would be a
wise decision or not, or whether I'm just not running the TNII carb
properly.
Thanks for any thoughts, guidance offered
Andy