Tinman!

I'm dealing with a first YS. It is referred to, by the manual I got with it, as "YS Futaba 120-NC." So this is obviously a 120 NC, and indeed it has only the regulator and high needle for adjustments. Didn't realize it was so old (1998 or older, apparently).

My issue appears to be a too-rich condition. Fuel dribbled/dribbles out of the carb at idle, and the plane looks like it has a smoke kit on it in the air. The engine is mounted inverted.

After getting loads of conflicting advice at my field, I read up on YS on the 'Net. One of the things I read was that you need to get the idle down to 2,000 RPM in order for the regulator to not over-fuel the carb (at idle), causing it to spill out. For clarity, mine "spilled out" quite a bit (about 1-2 drips per second).

So I decided to start from scratch, if you will. I backed out the high needle two turns, set the regulator to about flush, and started it up.

Could not seem to get the idle down to 2,000 RPM so turned in the regulator screw. Did this to the point where the control was noticeably "in" (i.e., not even close to flush) and in fact was only about a half turn away from being totally closed. Could then get a decent idle at 2,000 RPM, and still noticed a lot of smoke on acceleration and when running at high RPM (without touching the high needle RPM at WOT was around 8,250). Could probably have backed out the regulator screw a bit, and still maintained a 2k RPM idle, but had to stop adjusting since I noticed fuel in the fuse (another issue I'm chasing!).

In any case with the regulator that far in, and the idle at 2K RPM, the dribbling was very much reduced (about 1 drip every 30 seconds, give or take).

Anyhoo, two cans of K2R later I'm about ready to adjust it again. (For the record, I had two stoppers blow out, a fuel line puncture, and a split tank that led to four or five dead sticks, one of which was not pretty. Hopefully that was just a bad spell and my fuel tank issues are over.)

Anyway, my fear is the plunger is leaking. While I do notice an RPM change after adjusting the regulator screw, the engine still seems rich. Plus, I've never read of anyone turning the regulator screw in as much as I have. That worries me, as I live in Arizona and don't want to burn up the engine if it's actually too lean.

Other than that the engine seems to run great. Love the sound, and after getting into a routine, can start it very easily (no more props kicked offat least not lately).

Soooo, any advice based on the info I've provided? I don't really want to send the engine in for service, so am hoping it's not the plunger. I'd be happy for now if I can perhaps eek out a few months of use. The fuel dribble itself doesn't bother me much, especially since it seems I can mitigate that by turning the regulator screw in (a lot!) and lowering the idle. But I am concerned with how MUCH I seem to have to turn in the regulator scew.

Thoughts?





Mike

Troy Newman

If you are having tank leaking problems it will drive you setting goofy. You need to make sure the tank can take the pressure.

I use Tettra tanks available from Central Hobbies. They are the best in my opinion for YS engines. They won't split or leak.


Your dialing the regulator all the way in like you have indicates some dirt or debris in the plunger seat. The dirt gets in the way and the plunger can't close all the way or soon enough. This is why you are getting the drip drip on the ground at idle. The regulator is not closing. When you added more spring pressure on the plunger you improved it...this indicates a problem...and its usually dirt and debris. You regulator is too far closed on the screw adjustment The plunger is letting fuel leak past. In a normal operation it will never need to be that far closed to work properly. What you have done is put enough pressure on it to keep it closed long enough to overcome some of the leakage past. Its not the solution....You need to clean out the regulator. Also in you tank escapades this is likely how you got dirt into the system.


So get a Tettra tank, and clean out the regulator and you should be golden.

Troy Newman
Team YS

Tinman!

Thanks much for the reply, Troy.

I opened the regulator and cleaned it up (diaphram, spring, plunger, etc.). Fuel tank is new and holds pressure OK now, but is not a Tettra (looking to order one now). Does seem like the tank swells a bit when really pressurized.

After firing the engine up I noticed adjusting the regulator seemed to make a much bigger difference now. Before cleaning it, it really didn't seem to make much difference, at least until it was really cranked in. After cleaning I could notice changes in just 1/8-1/4 turns.

But, alas, the fuel drip is backand it seems worse. Plus, it now seems to keep dribbling fuel even after the engine is killed. Kind of like a siphon effect.

I noticed fuel going into the carbwhile the engine was offfrom the regulator, which seemed to be causing the drip (after killing). Leaning up the regulator seemed to stop it, but not completely. Couldn't seem to stop the drip, only mitigate it. But, unless I am missing something, I couldn't lean out the regulator very much as the engine would start to shake when the throttle was advanced (i.e., no way to hit max RPM).

Any other ideas?

Also, does the advice I read about checking RPM changes at 4,000 in order to check regulator adjustment apply to this engine? Before I noticed the fuel drip on engine cut-off I thought I had the engine dialed in nicely: it seemed to hold 4k RPM OK, and didn't drip much. But after noticing the non-stop dripping after engine kill I went back to adjusting again and couldn't get it back without the drip returning.





Mike

Troy Newman

Well sometimes when the enigne shuts down it might give a drip........................................drip.. ...........................................drip this is becasue the reguator is not sealing 100% but consider that the tank is under high pressure 6-8psi. This drip is a very small minor leak in that plunger...If you release pressure from the tank and the drip stops then you are good.

If not then its likely you need some regulator parts. It could be that a piece of debris damaged the little silicone stopper. It is a small cone shape silicone stopper much like a toilet stopper. If it gets a little cut in it or something the results could be the slow easy drip.............................................. .......drip....................................... ...................drip when the tank is under pressure and the engine is not running.

I would say its not an issue the engine should run fine and just release the pressure after you land. If you can love with that the engine should run just fine.

If you decide to replace those silicone parts then do a new diaphram as well. Its likely it is a little deformed as this can happen over time.

part numbers are

Diaphram YSE0730
Plunger YSE0176


These are cheap parts about $3 each. Should should probably replace the gaskets too YSE2208

parst are available here:

http://www.centralhobbies.com/Engine...YS120NCEX.html


Troy Newman
Team YS

Tinman!

Thanks again, Troy.

In hindsight I prolly should have left well-enough alone after I had everything dialed in nicely, aside from the after-kill drip (which indeed stops when the pressure is relieved). Oh well, at least I'm becoming familiar with the engine.

Since the wind here in Arizona has been severe, I'll try tuning it up again this afternoon.

Oh yea, ironically I had just placed an order for the Tettra tank, and other misc items, before reading your reply. To be safe I ordered a plunger, diaphragm, spring (2), and spare screws. I noticed the ballast is no longer being made, so hopefully that isn't usually an issue.

Thanks again.



Mike

Troy Newman

Oh yes the Ballast.

Its not needed. It was designed for a single specific pattern manuever to "slow" the regulator response. Back in the day of this engine we flew a "new" manuever in pattern called an Hourglass. In this manuever there was a really long 45 degree Inverted downline, then the engine had to throttle up quickly to do the same length 45 deg inverted upline. So it was at idle say for 10-15 or more secs as the model came across the top at idle and pushed this long inverted downline....the it had to do a tight bottom corner to level flight then it had to imediately go to max power another tight 135deg corner and climb a long inverted 45 degree upline.

The problem was this....the engine would load up on the long idle...so when you needed full power right now...the engine would not cleanly accel through the midrange. So it would get to full power but not instantly. So guys started to lean the regulator down to keep it from loading up...

Now when they punched it at the bottom it would accelerate quickly but sometimes it would go really lean and burp.

The Ballast was a solution to that manuever. It kept the engine from loading up a little at idle, and if you got it just a little lean it would help keep the burp from happening.

Long story short....the ballast worked, but a properly sized air bleed hole in the butterfly also worked.

Back on the 120NC there was not a air bleed screw to adjust...however there is an air bleed hole in the butterfly side of the throttle barrel. On the newer engines the air bleed screw adjusts the size of that hole. On the 120NC that hole was fixed at a given diameter.


So in the end you are good to go with or without the Ballast. It doesn't make any difference unless the engine is going to idle for a really long time and then need to accelerate instantly to full power.

The part is not longer used in any engine, and you can remove it or leave it in...it won't change much. Maybe and its pretty unlikely it will affect the regualtor adjustment just a little tiny bit.


What it will do is slow the response to change that you make to the regulator while its running. It will take an extra 5-10secs for the change to take affect. So just be careful when adjusting it it will take a little time for the adjustment to have an affect.


Troy Newman
Team YS

Tinman!

Update...


OK, since I wasn't 100% how the regulator worked when I cleaned it, I decided to do it again. This time I was much more aware of how it operates, so was careful to clean the area around the plunger, and the hole it sits in.

I also switched to YS 20/20 fuel, as I had been using Cool Power 15/18 (with an extra 2% of synth oil added to bring it to 20%).

Adjusted regulator to about level, and high needle two turns out. Fired right up, and I dialed in the high at around 8,200 RPM. Seemed to run a bit rich at 4k RPM so turned in the regulator screw 1/4 turn. Let it sit, readjusted high end, ran it at 4k RPM again. Seemed to hold RPM OK. No drips after engine was shut off.

First flight plane seemed to run well, though still a bit rich (but not smoke-kit-like rich). Definitely more power than ever before, and the engine sounded much smoother around mid-range. After landing and taxiing back in I noticed there was no dripping after I killed the engine.

There is still a slight drip when at idle, but nothing like it was before. I can live with it, and I should note I'm idling closer to 2,200 than 2,000. I usually give throttle an extra 3 clicks before take-off too (subtracting them before landing). Anyway, if it only dripped this little from the get-go it wouldn't have been enough to start this thread.

So to anyone reading this with drip issues, pay close attention to the plunger, and understand that that little rubber part is responsible for getting fuel to the engine. It's critical.

In any event, thanks again Troy. I feel I have a pretty good understanding of the engine now.





Mike

indyrcpilot

I have an older YS-120 that I've been flying in a large P-47 for several years. It ran great until recently. The first hint of a problem was when I noticed a new sound at low throttle settings - sounded like it was sucking air and was losing power. The problem seemed to go away, but then returned.

I pulled the cowling off to try to troubleshoot and noticed that there was a LOT of fuel dripping out of the carb at idle. Tried adjusting the regulator, but it didn't seem to help.

Frustrated, I sent the engine off to have it repaired. Reinstalled it on the aircraft when it came back and tried it out. It was better, but the sucking sound was still there as was the fuel drip.

I called the folks I had sent the engine to and they told me that they test run every engine after they repair them and that mine ran fine. They ran it upright though and wouldn't have seen the fuel drip.

I've since done some investigation online, including finding this thread. I'm going to try some of the things mentioned for the fuel drip and see if they work for me. I'd really like to get this thing running well again.

Any idea what might be causing the sucking sound?

Thanks!
Chuck

microdon2

My Feedback: (47)

Hello fellow YS owners. I recently picked up a used YS 140 Sport - great engine, but it kicks out a LOT of smoke at mid and WOT. (And I'm assuming lots of smoke means the engine is wasting fuel \ not running at best efficiency.) (I have checked the lifter gaps - they are good at .002). I tried closing the HS a bit, but, on next flight, the engine bogged-down at WOT - seemed too lean. So I re-opened the HS. Should I instead close down the Regulator valve to reduce the smoke? Or are YS engines supposed to kick out lots of smoke? (compared to an OS 120 4s, for example).

Also I noticed a fuel leak coming out of the cylinder head area. Will take a look - could be loose bolts or possibly a bad cylinder gasket (?). Are there any other leak possibilities? For ex - the fuel intake manifold?

Thanks.

Mike D

Jim Schwagle

My Feedback: (1)

YS's will smoke more than others, they don't like lean. Is it running smoothly? Don't tune to remove smoke, tune for how it runs and idles. 2000 rpm idle, rapid acceleration on throttle up. Are you running 20/20? It will run on lower nitro but becomes harder to tune. The fuel system must be pristine, otherwise you'll have problems. Good filters everywhere, good tank (Tetra is the best in my opinion, to take the pressure, but others use Sullivan or DuBro). Track down and eliminate all leaks. When done, the 140 will be a sweet engine. Run it on a stand or with the cowl removed, and look it over well. Gap setting? In metric, 0.04 - 0.1mm. If yours is in inches, then ok.