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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › os 70 eng. dilema? hard to start? pls help?
04-21-2009 02:48 AM  9 years agoPost 1


too cold here

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hello.. just got an used 60size raptor with an os70 engine.. it is very hard to turn over, no it's not hydro locking, in order to start it, i have to loosen the plug.. to releave some pressure, then tighten it when it starts..even after flying when the motor is warm it will not turn over..looked at the engine.. head shim in scoring.. all is well.. any ideas's...

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04-21-2009 02:52 AM  9 years agoPost 2


Futaba City Z (Mobara)

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Check the bearings
Check the bearings, Take the back plate off. Piston and sleeve check them, Take the glow off try truning the motor.
Thats just my 2 cents

AMA 334000

04-21-2009 04:07 AM  9 years agoPost 3

rrKey Veteran

Wagoner OK USA

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what type of starter are you trying to use to start it with? I have a 70 and I use a 18v battery on mine.

Trex700N, Trex600N, Raptor70, RaptorTitan, GMPCrickett, Visa

04-21-2009 05:03 AM  9 years agoPost 4


Cedar Rapids, IA

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Your starter, starter battery, and/or starter wiring would be the first place to look.

My Hobbico Torquemaster 90 with a couple of 6-cell "C" sized car nicad packs never had a problem turning my OS 70 over, even on cold days.

Replace the 6-cell packs with 7-cell packs, and the darn thing works even better.


* Making the World Better -- One Helicopter at a time! *

Team Heliproz

04-21-2009 06:20 AM  9 years agoPost 5


Mexico city

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I have also had problems to start an OS 70. I noticed that even a fresh 12v automotive battery turns the crank over, but not fast enough. besides it gets jammed at times because of the natural engine compresion.
Now I use 5s1p A123 LiFe cells that produce 16.5v and turns the crank with no hesitation. Ofcourse, the engine starts much easier.
I think any type of battery that delivers 14.5v and above will do the trick.
If you are able to turn the crank by hand, while holding the start shaft, then your engine compresion (or motion) is not abnormal, it just needs more power to get it started.

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04-21-2009 12:49 PM  9 years agoPost 6
Yogi 1


Clinton,CT USA

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I have a Dynatron starter with two 3300mah 6cell nimh packs and have no trouble turning the motor over. Before starting try backing the flywheel/fan off compression upstroke.Yogi

Velocity Is A State Of Grace Get Some Now !

04-21-2009 01:44 PM  9 years agoPost 7


too cold here

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man i would have never thought it would be the starter.. i do have the hobbico using car battery.. i'll have to buy a 4 or 5 cell lipo battery..
thanks every1..

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04-21-2009 02:55 PM  9 years agoPost 8


From Argentina now in Costa Rica

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I guess it has to be a combination of cold weather and starter.
Here I have no problems starting my OS70 or the 91 with the hobbico 90 and a 7amps 12v lead batt.

The only time I had trouble was once that the heli sat for a long time and the engine was a bit dry with old oil in it.

I guess the cold weather (where ever you are "Location: too cold here" might have to do with it...

Intelligence chases me, but I'm a lot faster! Fernando

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