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What's unreliable about the ROS 125 Engine?


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I'm debating getting a Backbone Stronger 125. It uses the ROS 125 or the ROS Lighter 125 engine.

People on here have said that these engines aren't very reliable - what tends to break and how easy is it to fix? Locals where I'm at use a couple of Backbone Strongers. They haven't had any real issues other than replacing a spark plug, which seems pretty routine to me...

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Hi - Just some info really..

I have recently acquired a Ros 125 -a newbie to the sport myself and recently had the manual pull start spring go on it - got it fixed easily enough though - but whilst looking for parts, I found 2 suppliers - PAPTEAM in Italy and Kangook in Australia, who both deal in original ROS parts....(couldnt see anyone in the UK that stocked the parts)

So, I emailed Ron at Kangook about the ROS motors general characteristics, what it was like etc - explained that I am new to the sport - here was his reply

Hi Paul,

The Ros 125 is a good motor. I have personally chosen to fly the Ros for the last 4 years. Good motor, and easy to work on.

I was quite heartened by that response...although at the end of the day it is still a 2 stroke motor and something will go wrong at some point...

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Absolutely - I used to work in forestry years ago and our chainsaws had the same starter mechanism design and they would break from time to time - not often though..so I wouldnt have though that you would have had to pay particular attention to it as a weak point on the Ros...

Which leads me to the pulley (over the shoulder starting for in flight restarts)

Right now, I dont have the pulley in use, so the starter cord retracts fully to the casing, down the back of the frame, which would be unreachable in flight. So, I am going to get the pulley put onto a piece of stainless, screwed to the frame..

For anyone who uses this method - how hard is it to restart the engine, pulling over the shoulder? Is there a technique - a knack??



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You can get parts for the ROS 125 easily direct from the manufacture: http://www.rosmotor.it/home.html

email: g.marcolini@marcmotor.com

I've found them very helpful, and they provide a good service.

I've had a ROS 125 for a few years now, and am happy with it, the things that I've had to replace are:

- Exhaust (snapped at weld points);

- Piston and cylinder (locating pin on the piston came out and scratched the cylinder);

- With the old exhaust the springs broke a few times (all fine with the new one though); and

- One of the reduction cogs snapped in two.

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