ys63s air bubbles.
01-06-2008, 06:35 PM
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ys63s air bubbles.
Hi troy, I have a 63s for about 2 years now and its been 100% awesome, but today it was not wanting to give full power and deadsticked 3 times on me which has never happened before. After checking it out i could see some air bubbles in the regulator to carb line, but no air in the tank to reg line, does this mean the diaphragm is shot??. there was more air bubbles at tick over than higher rpm.
its in a fliton inspire 60 and was its 1st outing in this airframe, it has pretty long lines as the tank is on the cg.
Any help thoughts would be great.
Jim Lacey
its in a fliton inspire 60 and was its 1st outing in this airframe, it has pretty long lines as the tank is on the cg.
Any help thoughts would be great.
Jim Lacey
01-06-2008, 07:09 PM
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RE: ys63s air bubbles.
Some air bubbles can happen from foaming in the fuel tank.
If the bubbles are small its not that big of a problem especially at idle rpm. What happens is the fuel in the tank and up to the regulator is under pressure about 5-8psi. Then after it leaves the regulator it is no longer under pressure so any bubbles that were small and could not be seen from fuel foaming in the tank from vibration, now expand and can be seen.
That being said.. Obviously there is something that has changed with your setup...
The question is where is the engine quiting in the air?
I would try a new glow plug. How long has it been since you had a new plug?
The I would start looking for an air leak somewhere. This leak could be from the fuel tubing going in and out of the regulator.
Air bubbles are not a sign of a diaphragm being bad....In most cases the deformed diaphragms can't cause air bubbles. In fact I would say a bad diaphragm will not cause air bubbles....UNLess it has a hole in it, or its so severely deformed or cut that it doesn't seal on the edges. If this happens you will get more than just some air bubbles.
To me the first step is to look at the plug. Next step is to look at the fuel tubing, and then start to look at maybe the fuel....Is it a new gallon? can you try some from another batch? Can you try a fresh gallon? Can you run this same fuel in another engine will no changes...if the second engine acts the same then perhaps its a fuel issue.
Normally small bubbles are not going to be an issue especially at idle. If the bubbles are larger and really affecting fuel flow then yes....Start looking at gaskets. First in the regulator then look to the carb and other spots. Air can get in that line from other spots and can show as if they are coming form the regulator. The external regulator though its likely a damaged fuel tube at the regulator or at the tank.
Troy Newman
Team YS
If the bubbles are small its not that big of a problem especially at idle rpm. What happens is the fuel in the tank and up to the regulator is under pressure about 5-8psi. Then after it leaves the regulator it is no longer under pressure so any bubbles that were small and could not be seen from fuel foaming in the tank from vibration, now expand and can be seen.
That being said.. Obviously there is something that has changed with your setup...
The question is where is the engine quiting in the air?
I would try a new glow plug. How long has it been since you had a new plug?
The I would start looking for an air leak somewhere. This leak could be from the fuel tubing going in and out of the regulator.
Air bubbles are not a sign of a diaphragm being bad....In most cases the deformed diaphragms can't cause air bubbles. In fact I would say a bad diaphragm will not cause air bubbles....UNLess it has a hole in it, or its so severely deformed or cut that it doesn't seal on the edges. If this happens you will get more than just some air bubbles.
To me the first step is to look at the plug. Next step is to look at the fuel tubing, and then start to look at maybe the fuel....Is it a new gallon? can you try some from another batch? Can you try a fresh gallon? Can you run this same fuel in another engine will no changes...if the second engine acts the same then perhaps its a fuel issue.
Normally small bubbles are not going to be an issue especially at idle. If the bubbles are larger and really affecting fuel flow then yes....Start looking at gaskets. First in the regulator then look to the carb and other spots. Air can get in that line from other spots and can show as if they are coming form the regulator. The external regulator though its likely a damaged fuel tube at the regulator or at the tank.
Troy Newman
Team YS
01-06-2008, 07:25 PM
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RE: ys63s air bubbles.
Hi Troy,
Ok, I fitted a new plug(os f) after the 1st deadstick which was aprox 5 mins into the 1st flight, all the fuel lines are brand new and i checked/replaced them at the field, the fuel was fine last week in this motor so it can't be that (magnum 20%), the bubbles could be from foaming but it looked fine on its way to the reg, i ran a few tanks on the ground and it would just quit at random times and only once or twice per tank.
The motor is not to lean as i could hold the head/barrel no probs after a run, and plenty of smoke.
Ive pulled the reg tonight and the diaphragm looks fine, nice and flat no holes or signs of wear. hmmm can it look fine and still be bad??.
Many thanks for your fast help!!.
Jim
Ok, I fitted a new plug(os f) after the 1st deadstick which was aprox 5 mins into the 1st flight, all the fuel lines are brand new and i checked/replaced them at the field, the fuel was fine last week in this motor so it can't be that (magnum 20%), the bubbles could be from foaming but it looked fine on its way to the reg, i ran a few tanks on the ground and it would just quit at random times and only once or twice per tank.
The motor is not to lean as i could hold the head/barrel no probs after a run, and plenty of smoke.
Ive pulled the reg tonight and the diaphragm looks fine, nice and flat no holes or signs of wear. hmmm can it look fine and still be bad??.
Many thanks for your fast help!!.
Jim
01-06-2008, 10:47 PM
#4
Senior Member
RE: ys63s air bubbles.
If the regulator looks fine it probably is fine.
Like I said it has to be really deformed of cut to not work properly. Check the fuel lines in your tank....
Next thing is the temps you are flying in....is it pretty cold? and have you re-checked the HS and low speed mixture settings?
It could be leaking air at the regualtor gasket(s).
Foaming: Like I said under pressure the bubbles will be tiny and not seen yet after the regulator the pressure is reduced and they will expand 10X or more their original size so if the bubbles are tiny this is why...if they are large like 1/8" then you have a leak somewhere which can happen. Check backplate and carb bolts. Head bolts....
Valve cover bolts?
Troy Newman
Team YS
Like I said it has to be really deformed of cut to not work properly. Check the fuel lines in your tank....
Next thing is the temps you are flying in....is it pretty cold? and have you re-checked the HS and low speed mixture settings?
It could be leaking air at the regualtor gasket(s).
Foaming: Like I said under pressure the bubbles will be tiny and not seen yet after the regulator the pressure is reduced and they will expand 10X or more their original size so if the bubbles are tiny this is why...if they are large like 1/8" then you have a leak somewhere which can happen. Check backplate and carb bolts. Head bolts....
Valve cover bolts?
Troy Newman
Team YS
04-01-2008, 12:50 AM
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RE: ys63s air bubbles.
Hi Troy,
I'm having the exact same problem with a YS .91AC engine. I was hoping you and Tetley would figure this one out for me. I've completely rebuilt the regulator, even to include replacing the body. All tubing to and from and inside the tank have also been replaced. This engine has about 90 flights on it in a Goldberg Staudacher S-300 GS so it has some wear. I've tightened everything you've mentioned so far but still have the same problem. At full run, after a second or two the bubbles begin to disappear and the engine sounds ok. The problem starts when transitioning to idle, bubbles start to appear and engine starts running rough and will quit. The bubbles I see at first are very small for just a second or two but then get larger as the engine begins to start running rough and slow down. (All the bubbles are appearing in the tubing between the regulator and the carburetor.) At midrange there is a constant flow of small bubbles but the engine will continue to run but sounds rough. Engine will not idle at all. Oh...I have to start at about 1/2 throttle, and milk the throttle until it warms up where I can bring it to full run. What else do I check?
Thanks a bunch!
I'm having the exact same problem with a YS .91AC engine. I was hoping you and Tetley would figure this one out for me. I've completely rebuilt the regulator, even to include replacing the body. All tubing to and from and inside the tank have also been replaced. This engine has about 90 flights on it in a Goldberg Staudacher S-300 GS so it has some wear. I've tightened everything you've mentioned so far but still have the same problem. At full run, after a second or two the bubbles begin to disappear and the engine sounds ok. The problem starts when transitioning to idle, bubbles start to appear and engine starts running rough and will quit. The bubbles I see at first are very small for just a second or two but then get larger as the engine begins to start running rough and slow down. (All the bubbles are appearing in the tubing between the regulator and the carburetor.) At midrange there is a constant flow of small bubbles but the engine will continue to run but sounds rough. Engine will not idle at all. Oh...I have to start at about 1/2 throttle, and milk the throttle until it warms up where I can bring it to full run. What else do I check?
Thanks a bunch!
04-01-2008, 02:01 AM
#6
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RE: ys63s air bubbles.
You have a leak somewhere. It is likely not in the regulator. Perhaps the carb bolts, airbox, or backplate bolts have been over-tightened and have warped the case parts. This is common on the airbox and the carb body.
What you do is remove the carb, and air box and check the surfaces against a flat piece of glass. You can lap these surfaces with some 600grit on the a flat glass surface. Then clean them up and re-install with new gaskets. Then don't over tighten the airbox screws or the carb body.
So you ask how can a leak in the airbox get to the regulator and fuel line before the fuel line even gets to the carb...well its because the regulator controls its pressure based on that in the engines case. At various times its a positive pressure and other times its a negative pressure. So its possible that this can happen. Another place to look is the throttle barrel seal. If this leaks it can generate air bubbles in the lines as well.
A new set of complete gaskets and o-rings. The engine is kinda old and might have some damaged o-rings. These o-rings are silicone and any contact with petroleum based chemicals will make them deteriorate.
New Glow plug?
Also check the fuel line fittings to see if they are loose of damaged. I think the 91AC has the screw in type fittings. These could be leaking. The newer engines don't have this style fitting but I know the older engines do. The 91AC has been around for along time. Like about 1994 was when it was introduced. The 91FZ came out about oh 1998 and then was replaced by the 110FZ in about 2003-2004
Troy Newman
Team YS
What you do is remove the carb, and air box and check the surfaces against a flat piece of glass. You can lap these surfaces with some 600grit on the a flat glass surface. Then clean them up and re-install with new gaskets. Then don't over tighten the airbox screws or the carb body.
So you ask how can a leak in the airbox get to the regulator and fuel line before the fuel line even gets to the carb...well its because the regulator controls its pressure based on that in the engines case. At various times its a positive pressure and other times its a negative pressure. So its possible that this can happen. Another place to look is the throttle barrel seal. If this leaks it can generate air bubbles in the lines as well.
A new set of complete gaskets and o-rings. The engine is kinda old and might have some damaged o-rings. These o-rings are silicone and any contact with petroleum based chemicals will make them deteriorate.
New Glow plug?
Also check the fuel line fittings to see if they are loose of damaged. I think the 91AC has the screw in type fittings. These could be leaking. The newer engines don't have this style fitting but I know the older engines do. The 91AC has been around for along time. Like about 1994 was when it was introduced. The 91FZ came out about oh 1998 and then was replaced by the 110FZ in about 2003-2004
Troy Newman
Team YS
04-01-2008, 09:44 PM
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RE: ys63s air bubbles.
Thanks for the quick reply Troy. I removed the engine today and replaced the Airbox O-ring and gasket. The cover was straight but the o-ring looked a little old and stiff, replaced the carburetor gasket as well. Also replaced the o-rings on the HS and LS needle valve assembly's. I tightened all the fuel nipples and none were found loose. The only thing I didn't replace was the throttle barrel o-ring, but it also appeared to be ok. I'll order a new one to replace it as well, just didn't have one on hand.
I reinstalled the engine and started it. When the engine's at full run I don't see anything and the HS needle is able to be adjusted. At about half throttle, very tiny bubbles begin to appear but the engine continues to run without much sign of a problem. At near idle the bubbles get larger and the engine leans out, slows and stops. I am able to get it to idle at some degree by opening the fuel regulator about a full turn (rich) and nearly closing the LS needle. It's now about 1/4 turn out but will idle for a short period before it eventually leans out due to fuel not getting to the carburetor. I'll replace the carburetor barrel o-ring when it gets here and see if that helps. I can't trust the engine the way it's running. Yes it's old, but the engine is still smooth and has good compression. I just hope the throttle barrel o-ring is the problem....I'm running out of options but I haven't given up yet!
Regards,
Johnny
I reinstalled the engine and started it. When the engine's at full run I don't see anything and the HS needle is able to be adjusted. At about half throttle, very tiny bubbles begin to appear but the engine continues to run without much sign of a problem. At near idle the bubbles get larger and the engine leans out, slows and stops. I am able to get it to idle at some degree by opening the fuel regulator about a full turn (rich) and nearly closing the LS needle. It's now about 1/4 turn out but will idle for a short period before it eventually leans out due to fuel not getting to the carburetor. I'll replace the carburetor barrel o-ring when it gets here and see if that helps. I can't trust the engine the way it's running. Yes it's old, but the engine is still smooth and has good compression. I just hope the throttle barrel o-ring is the problem....I'm running out of options but I haven't given up yet!
Regards,
Johnny
04-01-2008, 10:44 PM
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RE: ys63s air bubbles.
91AC not a 63S right?
What about your fuel tank system. If it touching the airframe....foaming fuel can cause these bubbles at idle.
From here try and richen the regulator a bit more......You didn't mention which fuel you are using either.
Factory setting of flush with the case is not always the right adjustment in all cases. I'm not really sure if the regulator adjustment is going to help....The air bubbles are coming from somewhere. Some tiny bubbles are pretty normal...but bigger bubbles leaning the engine out are not.
Try some richer regulator settings and see if it helps. Just leave the air bleed screw alone. You can't set that screw unless you are 2000rpm and the regulator is set right anyway.
Do the 4000rpm test on the regulator and see where its at. Obviously the engine is going lean so richen it up ...Try a bit more....
After you try it tell me where the regulator screw is in relation to the case housing.
Another option is the new regulator gasket/diaphragm on the 91AC means its probably not leaking. But make sure the screws on the regulator, air box, and carb are not over tighten.
Troy
What about your fuel tank system. If it touching the airframe....foaming fuel can cause these bubbles at idle.
From here try and richen the regulator a bit more......You didn't mention which fuel you are using either.
Factory setting of flush with the case is not always the right adjustment in all cases. I'm not really sure if the regulator adjustment is going to help....The air bubbles are coming from somewhere. Some tiny bubbles are pretty normal...but bigger bubbles leaning the engine out are not.
Try some richer regulator settings and see if it helps. Just leave the air bleed screw alone. You can't set that screw unless you are 2000rpm and the regulator is set right anyway.
Do the 4000rpm test on the regulator and see where its at. Obviously the engine is going lean so richen it up ...Try a bit more....
After you try it tell me where the regulator screw is in relation to the case housing.
Another option is the new regulator gasket/diaphragm on the 91AC means its probably not leaking. But make sure the screws on the regulator, air box, and carb are not over tighten.
Troy
