Hello Pros.
I #ve bought an older YS-53 second hand these days and try to run it smoothly. I've made some basic successes and some flights allready but I've had some bad inflight motorstops also.
I read a lot and fix some basic issues.

1. I'm using Rapicon Heli 20 (the best i could get in Germany)
2. 11/6 Prop
3. Fuelsystem is leakless and pressurizes fine. An oneway valve is installed.
4. Valves are set to 0.04-0.06 mm. the Cover is tight.
5. Regulator is flush

The Motor runs fine, but after a while at full throttle I can hear detonations and suddenly the Prop is off...
setting the carb rich, the engine has no power and looses speed till it dies.

Setting the air bleed screw for idle mix, I've noticed that it looks very different to the YS-63S I own also. the blueprints I've found online are different to (same as YS 63).
Is my YS-53 an really early version with a different layout? Do you have any sources for early YS? Can, and should I upgrade? Does the low end effect the full throttle?

Thanks for any help and please apologize my english!

YS engines will do that if set too lean. Try to rich the needle a little bit.

It looks like your engine is leaning out, it can be for several reasons,

Fuel tank is not holding pressure, you mentioned there's no leaks, is it a strong tank? like the Dubro?
If there is no leaks, all o rings are dry where visible, try richening the fuel regulator, 1mm at a time.
The idle screw does not make much difference.
Which glow plug are you using?

Regards

Is your regulator/midrange set correctly ?
Sometime the regulator may be too rich and then high speed needle would have been set too lean to compensate and then at full throttle it will eventually leanout and backfire.

Bring the engine down to 3500-4000 rpm and see if it holds the rpm or drops
if it drops then it is probably too rich and the regulator should be turned in a 1/4 at a time.

The 53 is a very troublesome engine and the settings range is very small.
If you do not have the gas port piston mod then you should do it.

Thank you for help, I'm really pleased!

I've examined my engine the last days - it's rainig all day - and took some pictures for further discussion... The main deal is, I think the engine was messed up and I have no experinced user nearby to aks how it should look like...

I think someone tried to change the Throttle Arm Set, but stoped halfway... You can see the actual status a the pictures.

I think at Picture 1 the screw C is wrong, I need a 'F5186 Low Speed Needle Valve' to fit in the hole D.
At Picture 2 you can see the screw A. This one looks like an awful replacement. No surprise I could not tune the idle with this.

I think I could fix it up with the throttle arm at the 'original' side... but is there any chance to change the side in a correct way?

@lennyk:
what is the gas port piston mod ? where can i find some instructions?

****UPDATE****

I've fixed some details... . I choosed the original layout of the throttle arm and borrowed the Low Speed Needle of my YS 63S. It looks much better now and make much more sense... I think I should test the engine know...

stay tuned!

you can read about the piston gas porting here
http://tech.flygsw.org/ysgasporting.htm

their diagram shows 3 holes, YS engines come from the factory with 4.

you would need to be comfortable with dismantling the engine and removing the piston
as well as being able to drill some small holes cleanly.

Hello guys,
I'm back from the field and had a very successful day, but I've to earn it very hard. First of all it was quite raini and I had to jump in and out my car the whole day... and fix the YS in my very small vw...

in the beginning the ys won't start or even had one ignition... then I could start it with a lot of throttle and it runs in the upper range but stop in the lower... So I double checked everything and detched the carb with anything without finding any problem. So I just stick it together and give it an other try (rain has just stopped) and it fires and runs...

So i could make the first tuning with your suggestions in mind... I've used an 11/6 and the full throttle was faster than 12.000 but i make 2 flights with a richer setting to examine the inflight behavier. then i switched to a 12/6 and tuned the max. at 10.000 it throws the Prop so I tune it at 9.500 and the idle was about 2.000. transition was fine. the reg seams to be good at 1 ccw from 'flush'. RPM are stable at any point. I think I'm ready to mount the cowling.

If you agree or not, pleas leave a comment! Thank you for your support!

I think the gas port mod is beyond my qualifikation - i will think about it.

Try never running the YS at peak needle setting, always back 200 or 300RPM from peak. That's the way I do it on all my YS from the 63 to the 170.
I have seen the engines backfiring at max power for being lean, and that's what happened to your engine, that can bend a valve, at least so it happening on a brand new 160.

Good luck with your setting and happy flying

Thanks for your advice,
I'm allways on the rich side of Life ;-)
Today I've found my final setting and enjoyed some flawless flights with mounted cowling - it has last one gallon of fuel to test around but now I'm ready for routine.

I can't wait to mount my stocked 63S in an Ultimate.

A hurray for YS and two thumbs up for this helpfull Forum!

http://www.youtube.com/watch?v=A5n4HW7A3es

Hello Guys - I'm back from field and very sad, because I've wrecked my bird...
I've lost the half of my Elevator inflight - just broke, no damaged, bad glue or anything... And, of course, I hit the only hard ground in the center of cornfield... Anything was torn to pieces and the YS is in bad shape. The crankshaft is broken. I don't know if i can get any supply for the older 53 in Germany, and the 63 has a bigger diameter - could i convert this parts? Any guess what's also broke - I can turn it and it 'feels' ok.

Would you repair or just buy an new one? I know it's a little bit difficult to guess, but I have to write this and get over it....