Fuel flow in YS 120
09-24-2007, 09:29 PM
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Fuel flow in YS 120
I'm new to YS engines, although I've had a fair amount of experience with other 4-strokes. I recently purchased a used 120 FZ
which I disassembled to replace the bearings. Other than roughness in one of the bearings the engine was in very good condition.
After reassembly, I'm having no success with starting it. The fuel tank develops presssure and feeds it to the
regulator but it will only pump fuel to the carb when I turn the engine in reverse of normal rotation. Normal rotation delivers no
fuel to the carb. Everything appears to be clean in the regulator, diaphram, check valve, and all the fuel passages. The regulator is installed with the little metal nub pointing toward the prop.
I'm wondering if I might have assembled something backward that is causing this. Any thoughts on this from the experts
would be appreciated.
Thanks!
which I disassembled to replace the bearings. Other than roughness in one of the bearings the engine was in very good condition.
After reassembly, I'm having no success with starting it. The fuel tank develops presssure and feeds it to the
regulator but it will only pump fuel to the carb when I turn the engine in reverse of normal rotation. Normal rotation delivers no
fuel to the carb. Everything appears to be clean in the regulator, diaphram, check valve, and all the fuel passages. The regulator is installed with the little metal nub pointing toward the prop.
I'm wondering if I might have assembled something backward that is causing this. Any thoughts on this from the experts
would be appreciated.
Thanks!
09-24-2007, 10:08 PM
#2
Senior Member
RE: Fuel flow in YS 120
Is it possible the fuel lines are reversed. Fuel supply goes to the front nipple on the exhaust side of the engine.
Pressure back tot he tank goes on the needle valve side of the engine.
If you have the regulator housing on with the protrusion forward this is correct. The other question is did you clean everything up when taking the engine apart and what did you clean it with?
YS engines have silicone parts and NO petroleum products are allowed. Petroleum will swell and destroy the silicone parts.
The other questions since are-build are the cam gear installed properly at the correct timing, and the other is the crank pin properly located in the rear disc valve...There is a big area next tot he proper crank pin seat. This would still make the disc valve move but it would not be properly timed and also when turning it backward the pin would move about 20degs of rotation before catching the edge of the disc valve or rotor and making it move... Proper alignment of these parts is critical.
Usually when we have a problem like what you are seeing its the regulator housing backward.
Troy Newman
Team YS
Troy Newman
Team YS
Pressure back tot he tank goes on the needle valve side of the engine.
If you have the regulator housing on with the protrusion forward this is correct. The other question is did you clean everything up when taking the engine apart and what did you clean it with?
YS engines have silicone parts and NO petroleum products are allowed. Petroleum will swell and destroy the silicone parts.
The other questions since are-build are the cam gear installed properly at the correct timing, and the other is the crank pin properly located in the rear disc valve...There is a big area next tot he proper crank pin seat. This would still make the disc valve move but it would not be properly timed and also when turning it backward the pin would move about 20degs of rotation before catching the edge of the disc valve or rotor and making it move... Proper alignment of these parts is critical.
Usually when we have a problem like what you are seeing its the regulator housing backward.
Troy Newman
Team YS
Troy Newman
Team YS
09-25-2007, 02:47 PM
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RE: Fuel flow in YS 120
Thanks for your reply Troy.
I was quite careful to put the camshaft in the same relative position as when I disassembled the engine
and have performed similar repairs on other types of engines in the past, however, I gave no thought as to the
position of the pin in the rear disc valve as I did not know this was critical. I'll pull off the backplate and
check this and give it another try.
Thanks again for the information!
Jim
I was quite careful to put the camshaft in the same relative position as when I disassembled the engine
and have performed similar repairs on other types of engines in the past, however, I gave no thought as to the
position of the pin in the rear disc valve as I did not know this was critical. I'll pull off the backplate and
check this and give it another try.
Thanks again for the information!
Jim
12-16-2007, 06:53 AM
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RE: Fuel flow in YS 120
I ALSO HAVE A YS120-NC AND I CAN'T GET ANY FUEL THROUGH THE REGULATOR. I HAVE THE LINE HOOKED UP CORRECT, PRESSURE IN THE TANK, AND THE REGULATOR BODY ON RIGHT. TRYING TO START THE MOTOR I AM NOT GETTING ANY FUEL TO THE CARB. ANY OTHER SUGGESTIONS?
12-16-2007, 07:13 PM
#5
Senior Member
RE: Fuel flow in YS 120
The regulator can get plugged up with oil and gunk that is dried out and turned to gel like stuff.
This is the main reason to not use a fuel with Castor oil. However sometimes from the way it was stored or handled the synthetic oils can do it to.
Remove the regulator housing and flush with raw fuel. These is a small silicone diaphragm in there clean it off with raw fuel and wipe it dry. Look for deformation or damage to the diaphragm. It should be a round disc about the the diameter of a penny.
Attach fuel line to the engine supply nipple and pressure nipple and pump raw fuel through these with the regulator off.
Next pump raw fuel through the check valve and make sure it is opening and closing by blowing through it in both directions.
Put the engine back together. Get it ready to start and remove the High speed needle valve. With the HS needle out of the engine turn the engine over with an electric starter. It should flush any gunk out of the needle valve seat.
The next possibility is if you used after run oil that had petroleum products in it. These petroleum based oils will attack and damage the silicone parts in the engine. Especially the regulator. If this happens then the pressure regulator will not work. Most times this type of damage causes the regulator to no close, but if the oil and gunk was left in the regulator over time it could cause everything to seal up.
You will see the parts melted and deformed when you remove the regulator housing to flush the parts.
Troy Newman
Team YS
This is the main reason to not use a fuel with Castor oil. However sometimes from the way it was stored or handled the synthetic oils can do it to.
Remove the regulator housing and flush with raw fuel. These is a small silicone diaphragm in there clean it off with raw fuel and wipe it dry. Look for deformation or damage to the diaphragm. It should be a round disc about the the diameter of a penny.
Attach fuel line to the engine supply nipple and pressure nipple and pump raw fuel through these with the regulator off.
Next pump raw fuel through the check valve and make sure it is opening and closing by blowing through it in both directions.
Put the engine back together. Get it ready to start and remove the High speed needle valve. With the HS needle out of the engine turn the engine over with an electric starter. It should flush any gunk out of the needle valve seat.
The next possibility is if you used after run oil that had petroleum products in it. These petroleum based oils will attack and damage the silicone parts in the engine. Especially the regulator. If this happens then the pressure regulator will not work. Most times this type of damage causes the regulator to no close, but if the oil and gunk was left in the regulator over time it could cause everything to seal up.
You will see the parts melted and deformed when you remove the regulator housing to flush the parts.
Troy Newman
Team YS
12-18-2007, 05:39 PM
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RE: Fuel flow in YS 120
TROY THANKS FOR THE HELP.I CHECKED ALL OF THATOUT, AND EVERYTHING LOOKED GOOD. I CALLED YS AND THEY TOLD ME TO MACHINE THE RAISED NIPPLE ON THE REGULATOR FLUSH TO ALLOW THE BRASS PIECE TO PUSH DOWN ON THE RUBBER PLUNGER. I NOW HAVE FUEL FLOW AND THE ENGINE RUNS, BUT THE REGULATOR SCREW IS TURNED OUT ABOUT 2 TURNS PASSED FLUSH TO TAKE THE THROTTLE. IS THIS NORMAL?
12-18-2007, 08:28 PM
#7
Senior Member
RE: Fuel flow in YS 120
Every engine will be a little different. You did some grinding to the plunger so that will change the setting a little. The brass screw reference ot the case is only reference. Chnaging that plunger will change that standard reference setting. Typical settings are within 1 turn either way of the flush setting anyways so you are close. You fuel and situation will determine the setting anyway.
Glad Richard got you hooked up.
Troy Newman
Team YS
Glad Richard got you hooked up.
Troy Newman
Team YS
03-09-2008, 03:55 PM
#8
Member
RE: Fuel flow in YS 120
Troy,
I also have the 120. My problem is I'm getting too much fuel , specially on idle. I'm noticing large amount of fuel coming ou t the card, engine starts to run erratically then cuts. Would this just be a case of close the regulator a bit to limit the amount of fuel. I would imagine this would have something to, do with also not getting a ggod idle. Does not seems to be constant. Please advise.
gary
I also have the 120. My problem is I'm getting too much fuel , specially on idle. I'm noticing large amount of fuel coming ou t the card, engine starts to run erratically then cuts. Would this just be a case of close the regulator a bit to limit the amount of fuel. I would imagine this would have something to, do with also not getting a ggod idle. Does not seems to be constant. Please advise.
gary
03-09-2008, 06:04 PM
#9
Senior Member
RE: Fuel flow in YS 120
Dripping fuel from the engine at idle is a function of one thing and one thing only. The regualtor is not closing or staying open too long.
The causes for this are numerous.
The biggest cause is dirt or debris keeping the plunger from closing.
If the regulator screw is not putting enough tension on the plunger then yes this is also a cause.
If the plunger is damaged or the regulator assembly is not assembled properly, meaning operator error in that it was taken apart and not put back together properly.
The silicone parts in the regulator can get old and hard, perhpas a bad plunger that is not sealing, a diaphram that is cut or deformed, or the pin that is on the plunger is sticking.
There are lots of things that can cause the engine to leak fuel especially at idle rpm.
What happens when the engine shuts off and there is still pressure in the tank? Does it leak fuel then? If it does then its likely in need of regualtor parts. If it doesn't leak when the engine is shut off, and pressure is still in the tank, then the regulator is closing therefore its likely an adjustment meaning while running the regulator is not closing soon enough and its too rich. But if it drips after shutdown with pressure in the tank, then the regulaotr is not closing and its a parts issue.
Considering there has not been a YS 120 produced in many many years, like at least 5 years for the 120FZ and about 8+ years for any of the 120 engine prior to the 120FZ I would say a problem showing up today is either dirt or damaged parts.
Troy Newman
Team YS
The causes for this are numerous.
The biggest cause is dirt or debris keeping the plunger from closing.
If the regulator screw is not putting enough tension on the plunger then yes this is also a cause.
If the plunger is damaged or the regulator assembly is not assembled properly, meaning operator error in that it was taken apart and not put back together properly.
The silicone parts in the regulator can get old and hard, perhpas a bad plunger that is not sealing, a diaphram that is cut or deformed, or the pin that is on the plunger is sticking.
There are lots of things that can cause the engine to leak fuel especially at idle rpm.
What happens when the engine shuts off and there is still pressure in the tank? Does it leak fuel then? If it does then its likely in need of regualtor parts. If it doesn't leak when the engine is shut off, and pressure is still in the tank, then the regulator is closing therefore its likely an adjustment meaning while running the regulator is not closing soon enough and its too rich. But if it drips after shutdown with pressure in the tank, then the regulaotr is not closing and its a parts issue.
Considering there has not been a YS 120 produced in many many years, like at least 5 years for the 120FZ and about 8+ years for any of the 120 engine prior to the 120FZ I would say a problem showing up today is either dirt or damaged parts.
Troy Newman
Team YS
03-10-2008, 12:55 PM
#10
Member
RE: Fuel flow in YS 120
Troy,
Appreciate the very quick responce. Once the engine shuts off, fuel still remains leaking but not for too long. Plus there is still pressure in the tanks. So do i need parts or adjustment.
Another question. Are you aware if there is support for YS in South Africa. I have no preferance where i get parts or send a motor for service. My only concern is time. More time waiting less time flying. We all want the best off both worlds..
Gary..
Appreciate the very quick responce. Once the engine shuts off, fuel still remains leaking but not for too long. Plus there is still pressure in the tanks. So do i need parts or adjustment.
Another question. Are you aware if there is support for YS in South Africa. I have no preferance where i get parts or send a motor for service. My only concern is time. More time waiting less time flying. We all want the best off both worlds..
Gary..
03-10-2008, 01:09 PM
#11
Senior Member
RE: Fuel flow in YS 120
I would try the adjustment first.
Perhaps the spring has weakened and it just needs a little more tension on it to hold the plunger closed. This doesn't mean the spring has failed just that it is weaker than it was say 4-5 years ago.
Try the adjustement.
Sorry I have no information about your service options. I am not directly affiliated with Yamada, only YS performance, and YS parts and Service. So for me to speak on behalf of Yamada is not my place.
Sorry
Troy Newman
Team YS
Perhaps the spring has weakened and it just needs a little more tension on it to hold the plunger closed. This doesn't mean the spring has failed just that it is weaker than it was say 4-5 years ago.
Try the adjustement.
Sorry I have no information about your service options. I am not directly affiliated with Yamada, only YS performance, and YS parts and Service. So for me to speak on behalf of Yamada is not my place.
Sorry
Troy Newman
Team YS
