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Decompression Button -ROS 125


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Hi, - before I say anything -just to let you know, I am new to the sport

My ROS 125 has this decompression button, which seems to make it easier to pull start, if I press it in. Once started the button pops back out. I dont have the pulley and extended pull cord set up for restarting mid air  - but was wondering even if I did - I wouldnt be able to reach the button before attempting to pull start  - and if I cant reach it it would be very difficult to pull because of the higher compression.


So - how would l deal with the situation of restarting the engine in mid flight? Is there some mod that can be done?





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On my ROS125 I can't crank the engine even with two hands if I don't decompress it first. 

The decompression kit is extremely, extremely rudimentary and you can make one yourself with just some thin steel wire, a crimping tool, and something to crimp into the wire to allow you to grab it easier. 

I'll shoot a video of the setup tomorrow on my Backbone 125. 

IMO having a way to decompress the engine is mandatory if you want to restart the engine in midair. 

I practiced this a few times before - fly up, kill the engine, feel for the tip of the pull cord that leads to the decompression plug (it's mounted next to my primer bulb and can be felt through gloves - the primer bulb is a good place because you also use it to flood the engine should your kill switch ever refuse to work), give it a tiny pull, and then yank the pull starter. Starts right up in midair.

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Here's the video that I shot complete with a small bit on the pulley pull start: 

The bit that really seems to help is for the decompression plug on the engine to have a hole drilled through it already so a steel wire can be threaded through it. I'm not sure if you have this hole already on your motor. The hole drilled into the cooling fin on the motor is also helpful but I suppose you can find another place to securely mount the other end of the wire to create the tension necessary to push the decompression button back in.

If you try and do this yourself, just make sure that there is zero, and I mean zero, chance that either end of the wire can come loose and fall back into the propellor mid-flight. Having a steel cable fall into the prop would be an insta-kill for your prop and maybe even the part of the chassis that the wire is attached to.

And after thinking about it, it would be nice to have the knobby bit mounted over the shoulder, somewhere close to the pull start, rather than down next to the primer bulb. You want to start the motor, so your right hand is naturally up over your right shoulder. Having to move it down to where your primer bulb is and then move it back up to where the pull start is is a bit of a pain in the ass.

Edited by fuzzybabybunny
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Excellent video and very informative! I will follow what you have done and be very careful about the steel wire. With my engine the pull cord is not yet on a pulley (so the handle retracts right back down to the starter casing) -  and so I am wondering if I need to extend the cord length to do that - and how I would go about that - got some more research to do I think.. Thanks again -its very much appreciated!

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  • 1 year later...

Digging up this old post as it is now relevant for me. What a lovely simple solution for remote operation of an awkward to get to button. I had been assuming there was no choice but to make a pivoting lever to do this but that is far more simple and elegant. Many thanks.

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