First experience with Bubble Jett tanks
#1
First experience with Bubble Jett tanks
I just finished and flew a new Outlaw yesterday. I outfitted it with a NOS OS .32SX and my first Bubble Jett fuel tank. I had trouble with the engine flooding and had to keep hemostats on the fuel line until I had the igniter on the plug and starter in hand or else I would get hydraulic lock in just a matter of seconds. I also had trouble with the mixture enriching and dying out at low and mid throttle.
The engine has very little run time on it so I was intentionally running it a few clicks rich, and the low end needle can probably be leaned out a tad. But even at half throttle it seems to be drowning.
Is this the typical experience with these tanks or have I set up something incorrectly?
The engine has very little run time on it so I was intentionally running it a few clicks rich, and the low end needle can probably be leaned out a tad. But even at half throttle it seems to be drowning.
Is this the typical experience with these tanks or have I set up something incorrectly?
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RE: First experience with Bubble Jett tanks
its likely that the tank requires you not set the needle valve as rich as a conventional tank allows. not having any air in the tank means that it never or seldom loses its siphon prime...
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RE: First experience with Bubble Jett tanks
Are you overfilling the tank on the ground? Or is this happening in flight too?
I always pinch the fuel line, disconnect the filler, then aim the fuel line away to ensure no residual pressure from overfilling - it is easy to do this, and it can last a few seconds to cause nightmares during startup, exactly like you describe, at worst you can tear the bladder. Haven't burst one yet, but I have watched a few cc's of fuel squirt out after disconnecting. It takes the engine a bit to burn off that fuel, so connecting it at that stage results in pressure feed and flooding, hydraulic lock etc. Make sure there is no pressure before connecting to the carb.
I wouldn't hesitate to lean the low end to a good operating setting right off the bat. There is far less heat being generated, and you do not want the engine to cool further. It's the top end to keep a bit on the rich side.
MJD
I always pinch the fuel line, disconnect the filler, then aim the fuel line away to ensure no residual pressure from overfilling - it is easy to do this, and it can last a few seconds to cause nightmares during startup, exactly like you describe, at worst you can tear the bladder. Haven't burst one yet, but I have watched a few cc's of fuel squirt out after disconnecting. It takes the engine a bit to burn off that fuel, so connecting it at that stage results in pressure feed and flooding, hydraulic lock etc. Make sure there is no pressure before connecting to the carb.
I wouldn't hesitate to lean the low end to a good operating setting right off the bat. There is far less heat being generated, and you do not want the engine to cool further. It's the top end to keep a bit on the rich side.
MJD
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RE: First experience with Bubble Jett tanks
The carb is low on a side mounted engine so you could get siphoning regardless of the tank.
If you do a good job of drawing all the air out of the bag, then just fill it with just enough fuel to avoid any pressure build up, you should be good to go. With a 3 line set up, I don't bother with sucking the air out, I just fill the tank until fuel runs out the overflow line, then plug it off.
If you do a good job of drawing all the air out of the bag, then just fill it with just enough fuel to avoid any pressure build up, you should be good to go. With a 3 line set up, I don't bother with sucking the air out, I just fill the tank until fuel runs out the overflow line, then plug it off.
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RE: First experience with Bubble Jett tanks
Oh yeah, Outlaws are side-mounted aren't they. Low carb, siphoning. Good call CP. On a bubblefree tank the fuel pickup is effectively on centerline, not at the bottom of a clunk tank - or so the mfg lit says.
MJD
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RE: First experience with Bubble Jett tanks
Once you feel the pressure of the bag being full, pull just a little fuel back out with the syringe and clamp off the fuel line. Hemostats work, but these little clips are reallyl slick, just place them over the fuel line and they stay with the plane and you don't have to worry about lose them. Right before your ready to start the plane, unhook the clip and it will start right up (no need to prime).
I found them at this link, but I just buy them at the local hobby store.
http://www.rcslot.com/pc-radio-contr...om%2Ffuelgrid3
I found them at this link, but I just buy them at the local hobby store.
http://www.rcslot.com/pc-radio-contr...om%2Ffuelgrid3