OS 50 SX-H tuning

[Leebert]

Hi all
Just been flying and there were comments about the fog my Rappy 50 V2 was creating. I tried leaning off the needle a couple of clicks and nothing changed so I put it back. What sort of low and high speed settings are a good starting point and is there an newbie set-up method that I could look into?
I'm running Magnum 12% on a standard OS pipe (I think) - what sort of levels of smoke should I expect?
I was practising hovering at the time - no full power stuff.
Cheers

[Ade_Law]

magnum is quite smokey. If the engine is producing power and running cool leave it.

there arent many fuels you can tune on smoke these days, most will smoke a fair bit even when lean.

Ade

[Leebert]

Hi Ade
Thanks for the reply. I know Magnum is a bit smoky but this is really foggy!
The motor seems to bog down a bit as I spool it up from idle - at this point the exhaust cloud is pretty dense.
Is there a setting method or is it an experience thing?
Cheers

[Ade_Law]

is it an SX-H or or Hyper (blue head)?

the sx-h suffers from a lean mid range. This means you have to run the idle mixture fairly rich which will affect reliability at idle and pickup from idle.

you could try leaning the idle mixture slightly. But after a little a min of hovering check the engine backplate to make sure its not getting warm.

It might need the cateye mod but dont do it until somebody that knows engines properly has had a tinker with the mixture to make sure it really does need it.

Ade

[Leebert]

It's not a hyper, just the standard SX-h.
I don't know if the 'cat-eye' mod has been doe but I suspect not.
I seems I need to get an experienced heli pilot to look at it though - it drinks 12% nitro and I'm not doing any flash flying yet!
regards,

[Steve]

I've got one of those in my Sceadu.

I also suffer with some poor low to mid-range response on a standard Just Engines muffler. My mate uses a Muscle Pipe on his one and doesn't suffer with this problem at all.

What's a cateye mod?

Never heard of it.

[Leebert]

It's a mod for the brave apparently
There is a small slot with a hole in the centre in a part in the carb and it looks kind of like an eye hence the name. The trick is to file out one side out it very carefully to open up the eye on the side where it runs lean. At that point, it will now be running richer. Unless of course you file too much away, then it'll run richer than a rich thing or the wrong place and then its new parts time.

[jimbob]

Well you get a cat....

[Ade_Law]

as much as it pains me to put a link to RR

http://www.runryder.com/helicopter/t62377p1/

bare in mind that you dont need to take the engine out or completly dissassemble the carb.

just undo the nut on the side of the carb that holds the brass sleeve in and the brass sleeve and cat eye bar coms out in one lump.

the metal is a lot softer than it looks, it doesnt take much to take off enough.

Ade

[Steve]

Ade

Is this cateye mod really worth doing? I mean, does it really make that much difference? is it worth having a go?

[Janek]

I have 2 SX-H's and they both run perfectly (most of the time), without the cateye mod, but with the webbing mod.

You must be very careful with the cateye mod, if you shave off more that a knats whisker, you'll be into buying a replacement

[Ade_Law]

some engines are worse than others and it does depend on what you do with the model. If your just hovering then you just tune for the throttle you use and get on with it.

when you start throwing it around you use more of the throttle range so the problem will either show up as a rich idle (to richen the midrange), No power (due to rich top end to richen the midrange). or a lean midrange.

Ade

[Steve]

Webbing mod??????

Now what's that all about?

Also, if it's rich in the low to mid range, why not just lean it out a bit on the 2nd adjuster cam. Isn't that what it's there for?

[Ade_Law]

one of the reasons the sx-h was thought to wear out bearings was due to either not enough oil or too much oil in the rear bearing. so by taking the thin part of the crank web off you fix this.

however the real cause is due to the lean spot causing detonation and batterying the crap out of the rear bearing.

The 3 symptoms i showed you are caused by the same 1 thing but depending on top/bottom settings will show up differently. The mid range of the SX-H is lean.

[Steve]

ok

I'm jumping in with both feet. I've gone for the cateye mod. That bar is really very small, and only needs to be scared with a file to take some off. Will try and get up th efield tomorrow night to try it out.