How do I know if I have a Bad Motor? - RC Groups
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Apr 22, 2003, 08:33 PM
Registered User

How do I know if I have a Bad Motor?

My Hitec Sky Scooter is getting real doggy in it's performance. I use to be able to do all kinds of aerobatics but now it's just kinda Lazy. I am thinking that I either have a Bad Motor or Bad battery packs, Both the Motor & Packs are old. How can I tell if the motor is bad? I am charging up the Packs right now & will put my Multimeter on them to see what voltage they have. Does the Sky Scooter Pro have a Speed 400 or a 380 Motor?


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Apr 22, 2003, 09:43 PM
Registered User
rcav8r2's Avatar
Well the only <=400 motors I've truely worn out are the speed 400s in my Zagi. Went through 4 or 5 in about 4 years. In all the ones I replaed they would make "weird" clicking noises when turned by hand. Flight times and performance were down, and the motor was warmer than normal. Also there was a fair amount of arching seen when peaking in the slots by the brushes.
Interestingly enough I tore apart one of them ,and it looked fine, but it was definatly the motor in my case, because as soon as I replaced the motor all was well.

The speed 400s included with my Twin Star that has a LOT of flights ( first flown Aug 1998) and the motors are just fine, but I rarely go above 1/2 throttle with this plane.

OK I wore out 2 Atomic Forces and one Fusion in my Corona, but I'm only counting the <=Speed400 stuff.
Apr 22, 2003, 10:25 PM
Registered User
The Sky Scooter Pro has a Speed 400 6V

How long have you had your Sky Scooter, any idea of how many flights?

You might also check your gearbox and make sure it hasn't got itself buggered up.
Apr 23, 2003, 09:02 PM
Registered User
I am still using the STOCK Hitec Motor & this was a Sky Scooter Pro I that I converted to Geared. This motor probably has 40 flights on it maybe, the gearbox looks OK & my batteries tested fine for voltage. If I remember correctly, this is a either a Speed 400 or 380 Motor & I know it's 7.2V, would It be better to go with a 6V Motor?

Apr 23, 2003, 10:22 PM
Registered User
It sounds like your setup is the similiar to mine: SS Pro I geared. When I needed to, I replaced the motor with the 400 6V. I am running an APC 9x6 Slow Flyer prop geared 3:1 and I really like the way it flies. Lately I have been using 8 cell HECell packs and they work great.
Apr 23, 2003, 11:15 PM
Motor Maniac
You really need to measure your battery under load to determine if it is going bad. An unloaded bad battery will read about the same voltage as a good one. It isn't until a significant load is applied that the voltage sag really shows up. Best thing to do would be to find a friend with a good battery charger that can do discharges as well and has a digital display, then cycle the pack a few times and see how much capacity the charger measures. This seems to be the best way to determine if it is the pack.

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