I'm new to YS engines.. and I'm trying to get my ys 120 sf running, but it seems like you can't hand start the motor like you can on a diff four stroke... and when the prop spins I hear a small clicking sound by the prop shaft... could this be the regulator... You can hear it if you slowly turn the prop by hand.. Is it possible to get a ys to start by hand?? or do you use a starter each time... it just feels a lot different than other four strokes I've used and I don't know if this is b/c of the fuel system or if its b/c something is up with the engine...

thanks

Nelson Munoz

Actually if somebody would be willing to PM me their phone number or I can give them mine and maybe sorta walk me through the setup on this thing that would be super awesome...
or a post will work just as good

I posted this here b/c we all know the patter guys are the YS experts!!

Nelson,

I don't recommend hand starting the YS motors. They have very high power and as a result can get a little bite that can take your arm off. I have been flying YS motors for a very long time and I use a starter. Multiple reasons and the least of which is I have all 10 fingers and all 11 toes!

The small clicking noise you are hearing is probably the tappets on the valves and or the cam gear followers. This can be common when the motor is dry. Pull the valve cover off and check the tappet clearances. They should be about 2-3 thousands of an inch.

If they are extremely wide gaps this could be the clicks...You say it sounds like its down near the crank this is most likely the followers that ride on the cam. As they pass over the lobes of the cam sometimes they will click down onto the back side of the lobes. This usually happens when the motors set a while and the oil such is a little thick inside. It will go away after you run it. If the motor has set for a long time then run it for a a tank or two without touching the regulator. Chances are its a little gummed up with thicker oil and will clear out as the motor heats up and runs. Lots of guys let their motors set all winter then come out in spring and spend 4 days trying to dial the needles in....When they were fine to begin with...the motor just got thick oil in all the little nooks and crannies. In the YS pressure system there are lots of places a little dirt or thick oil will make a engine run poorly.

Next thing plumbing is important with the check valve and all. Go to the YS Performance website for instructions on how to hook up the plumbing, and how to set the needles. Blow through the check valve perhaps run fuel back and forth through it to clean out any oily gunk. This will keep the check valve from working properly and will cause problems with getting the motor to run.


Always remember the YS pressure system pressurizes the tank. So you need to make sure you have a good quality tank. Always release the pressure first before unhooking the fill lines. Go to Central Hobbies website and they have a good drawing of how to hook up the lines with T's to get the vent line open and keep you from hooking and unhooking to the motor each time you fuel.

http://www.centralhobbies.com/instructional/lines.html

This shows the setup for the FZ style motors. This is the same for the 120SF, 120NC, 120AC (sort of it has more lines and such), and 120SC as well. The 140's changed a little then came back to a similar setup.


The regulator has moving parts but they move with pressures and have silicone parts so you won't hear anything out of it.

I would stick some good fuel in it. Cool Power 30% heli fuel is an excellent choice and will make it sing. Maybe a 16-8 prop maybe a 15-10 depending on your needs. And use a starter! These things can kick back. Now after you get the motor setup and all is working great...Sometimes a talented snap of the finger can start them...But I stopped doing that years ago. My Talented finger worked half the time and a starter was always on hand anyways. By no means flip the prop like you or I would an OS 46....These higher compression higher output motors will often backfire if they get a little wet and they have 3+hp to take off your digits.

I always recommend using high nitro in 4 strokes. They run and idle better on it. Makes the mixture setting less sensitive and critical. I would say always run 20% or more nitro. They will run on 15% but it will not be as easy to setup or make as much power. Saito 4 strokes are the same way they like nitro.

Next thing on fuel use only a synthetic oil like Cool Power. Don't use castor. Really the synthetics are what you need. There are lots of little passages and such that fuel and pressure pass through. You don't want these to gum up with castor. Omega is the castor version of Cool Power. While some guys run it in their motors I stay very far away from it. I probably put 600+ flights on some of my YS motors every year. There have even been times I was putting 1000 flights year on my model. Synthetic oils are the best for this application no doubt.

Next thing OS #F or YS glow plug. Central Hobbies has about the best price on these like $5.30 each.


Troy Newman
-YS Performance

Troy,

Thanks so much for your response... One more question, the disc retainer screw on the back of the engine... how tight should it be??? If I just tighten it snug the engine turns fine.. anymore and it seems too tight??

Yeah the motor has not been ran in a while so I probably need to run it for a bit to get it right...

thanks

Disc retainer screw meaning the one with the left hand thread?


It should be tight. If the disc valve sticks then this screw is tight then there is something going on with the disk valve....Another thing to be aware of is if the motor has been apart...you need to make sure the crank pin is in the disc valve properly. If its not then you have the clicking noise you are describing. A new guy that pulls the motor apart will not realize that the crank pin fits in a specific part of the disc valve. Many times this gets put back together and its not aligned properly. I tried to run one a few years agao and it was not aligned properly. Would not even start up.

So if you have had it apart you need to make sure things are back properly. Its hard to describe the way it goes together even with words and photos....

But if you take it all apart (carb and backplate) you will see where the crank pin rides in the disc valve. Make sure this is properly aligned.

Troy Newman

Troy,
You have WAY too much time on your hands!!! But seriously, your YS advice is SPOT on!! Kudos!

Old Dawg,
Long Live Team Vegas!

hello Mr.Troy,
i run coolpower20% heli fuel on my ys engines, is that a castor fuel? is it ok?

most guys I know run either of these 3.......

20/20 cool power (sometimes called YS)
20/20 power master (sometimes called YS)
30% heli cool power

No one I know runs straight 20% or runs 4 stroke fuel. 20/20 is something different than 4 stroke fuel.

I run my YS63 on 20/20 and my YS140L's on 30%

All Cool Power is Synthetic oil. Now the CoolPower Heli fuels are orange in color and not green like traditional Cool Power.

This just signifies they have the Heli oil package and not the normal Cool Power oil package. It is still Synthetic just a low viscosity oil. This low Viscocity oil package is like 23% oil. The reason for the higher content is that it is a low viscocity oil so you need a little more volume. It works excellent in all YS engines.


A 20/20 fuel is also good in YS motors. This is 20% nitro and 20% oil. Back a few years fuel companies started making it and called it YS 20/20. It was done so that consumers would know that the fuel had its 20% oil content recomended by YS.


Morgan Fuels produces Cool Power fuel. They also produce Omega fuel. The Cool Power is all Synthetic and the Omega is a Synthetic and Castor Blend. Omega fuel is Bright Pink in color. The reason for the color changes is to tell us the modelers what oil package is in the fuel.

Troy

If the disc retainer screw is tight should the motor feel harder to turn like it has a good amount of compression... Its not that it wont turn at all its just harder to turn...

What do you mean by left hand thread??

The castor oil component is not one that I would use in a YS. It spells "Gummy"

Had quite a few sticking pushrod-assemblies due to use of castor. Once they ran synthetic only they had no problems.

Eric.

Nelson,

the disc valve should be attached with a screw that is a backwards thread. Meaning looking down on the top of the screw it tightens by turning it CCW rather than CW.

A Screw that tightens up CW is a right hand thread. This is what all the threads are on nearly everything. The problem is on the disc valve if it was a right hand thread it would loosen up as the engine runs. SO they make it a special left hand (CCW) thread so that the engine running keeps trying to tighten the screw rather than loosen it up.

It has been a really long time since I had one of those 120SF motors much less worked on one. If I had it in front of me I could tell you what was up with it....but its tough to describe from 10+old knowledge. The last time I had one of those motors was around 1994 and it was old then. We were running 120AC's which I still have a couple of those.


Troy

This is the back of my engine, the screw I'm talking about is the retainer screw in the recessed area in the middle of the backplate.. I guess it would be called a back plate... On mine this screw is a right hand thread screw... Hmmm..
The hole in the middle of the 4 screws holding on the backplate is the one I'm talking about,, the screw is recessed in the bottom of there...

Looking at that picture, I don't think you have an old 120SF, I think you have a 120 NC. There is some confusion, because the NC and SC still had the 120-SF logo on the side of the engine.

I live in North Raleigh, probably just a few miles from you. What club are you with? I fly at RDRC, and could meet up with you sometime to get this engine running.

You can hand start this engine, I do it all the time (in warm weather), but the safe thing to do is to use an electric starter. I have a technique I use to prime the engine that usually results in the engine cranking in one flip. And I still have all 10 fingers.

Bob R.