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HomeAircraftHelicopterGasser Model RC HelicoptersOther › prime bulb question
11-10-2005 03:12 AM  12 years agoPost 21
Pre-Mix

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Hi Torque,
Im glad that you got your problemns sorted. Life is too short to shelf a helicopter!
Im trying to understand why changing to new tubing would fix your problem. But, Billme mentioned to me that when he once used a "T" fitting on his return line for refueling he had similar unexplainable problems. When he removed the "T" and started refueling at the carburetor fitting his problems went away, much the same as yours. Billme was unable to explain why this would have an effect but said to try it anyway.
I did remove my "T" fitting and am still having fluctuating primer bulb fuel levels.

Here is a thought, could it be possible that fuel is splashing from the tank into the return line. As the tank tries to vent the air trapped in the return line between the fuel splashed from the tank and primer bulb expands from the pressure drop in the tank and is drawn out into the tank causing it to siphon fuel out of the primer bulb???
Next weekend I will also conduct more return line blocking to see if the bulb stays consistant as well as flying very mellow at 1/2 tank or less with the return line open to see if the "splashing fuel into the return line" theory has any effect on the primer bulb level.


Johan

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11-10-2005 11:45 AM  12 years agoPost 22
sparky666

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uk

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I also really fail to understand why changing an open too air return fuel line would correct such a problem.

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11-10-2005 02:43 PM  12 years agoPost 23
torque

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bolivia , north carolina

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pre-mix

thats funny. i failed to mention that i also had a "T" fitting in my return line. in my mind i could not understand why this maybe a problem due to the tank having a vent line. I did notice when i took off the old fuel line, the short piece of fuel tubing from the 90degree fuel fitting on top of the carb to the "T" was somewhat loose and worn. this is my guess where the problem was. so with new line and nylon ties around each fitting. the last 2 hover flights were fine, infact when i primed the bulb there was a small bubble in the bulb when i got done flying it looked like the bulb was empty. when heli stopped and i got up to it, here the bulb was completely filed, just 2 small bubbles about the size of a pin head could be seen in the bulb, so the bulb increased with fuel.

thanks again guys.

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11-10-2005 03:27 PM  12 years agoPost 24
Pre-Mix

rrApprentice

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right on!
torque,
very happy to hear that you got your problem sorted and you are welcome! Now if I can just get my barbi to behave, I too will be one happy camper. FCM came up with an interesting idea re: the routing of my vent line. I drilled a hole in the front strut to neatly hold the vent line away from the heli. What TCM suspects may be happeing is air passing over the vent from either rotor wash of FFF may be creating a venturi effect not allowing the vent to function properly. So I will create an unobstructed still air environment for the breather tube and see what happens. That certainly would explain the fluctuating fuel level in the primer as not all flights are the same. Some are FFF, others are hovering only etc. Will share my results purely in the interest of carbi science.

Johan

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11-10-2005 03:30 PM  12 years agoPost 25
Pre-Mix

rrApprentice

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correction!
oooohh ehhh sorry guys... thats CARBI...not barbi :-) I was an "e" away from a real embarrasment!

Johan

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11-10-2005 04:15 PM  12 years agoPost 26
AceBird

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Utica, NY USA

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QUOTE>>>

acebird, no i change the complete carb. both were 167's still had the same problem. BUT!!

Pre-MIx. i think you nailed it. I did as you instructed. i filled the primer bulb, blocked off the return line and the bulb stayed full. So i installed new fuel line from the return to the tank. and flew another half tank. and the bulb stayed full. thanks a million.

when i switched carbs it still had the old fuel line so the problem stayed with the changed out carb.

again thanks pre-mix and to everyone else that gave input. Torque

END QUOTE>>>

Torque,
On my first post #4, I asked you “what happens if you clamp the return line?” That is nine posts before Pre-Mix suggested to stop off the return line. Did you miss that or did you not understand what I was asking?

I am all for tapping into BillM’s knowledge and experience but if he said changing the return line would solve your problem I would be skeptical. The return line is an EPA (environmental) thing if it wasn’t there it would spill fuel on the ground. The sole purpose of the “air purge bulb” not “primer bulb” is to fill the supply line and one side of the diaphragm with fuel (less than 3cc). If you close the tank vent and the return line with the return line port open to atmosphere then shake up the tank, vapor pressure will fill the supply line and diaphragm on its’ own. After the supply is full, you could open up the vent line and it is just like any other two line system that has a fuel pump. This “air purge bulb” is totally unnecessary for helis.

By the way, are you running with a tank vent (three lines)? Some are only running with two (no vent line). Vapor pressure will pressurize the tank and will also tend to push fuel past the check in the bulb if it had an ever so small leak. This pressure would also affect the metering. Vapor pressure changes with temperature. So as the ambient temperature changes so does your mixture. Not a good thing unless you love to needle tweak!

I hate to say it but somehow I think your fix is only temporary.

I would be on the look out.

Ace

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11-10-2005 07:14 PM  12 years agoPost 27
torque

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bolivia , north carolina

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acebird,

in your post, i didn't fully get what you were saying about the return line. when pre-mix explained it, i got it. in a few post back, i thanked everyone, including you for the suggestion and help.

about the vent line (3 lines in the tank), yes i have a vent line. i have not heard anyone running just 2 lines. i didn't know that one could do away with the vent line. are you running 2 lines?

i just got done running to tanks , hovering in the yard working on my gyro set up. after the flights still had fuel in the bulb.

thanks again acebird.

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11-10-2005 08:25 PM  12 years agoPost 28
AceBird

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Utica, NY USA

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Thats quite all right Torque I have been miss understood before ... it has got to be me. That is what is hard about email, you don't know if your message is getting through clearly.

Still can't quite get the drift about changing the tube on the return line as your problem...

No I run three lines. I read somewhere that someone else was running without a vent line. You can run two line like you do with glow but one should be a vent.

Ace

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11-11-2005 02:20 AM  12 years agoPost 29
torque

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bolivia , north carolina

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acebird
i just spoke to "coastalTom" and he said that he run only 2 fuel line, no vent line, and has no problem. he said it pulls the fuel until empty.

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11-11-2005 03:25 AM  12 years agoPost 30
Pre-Mix

rrApprentice

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Hi torque and acebird,
acebird, I hope you dont feel like I took your idea with the return line. I actually got the idea from RR and may have been from you on a previous post. So you do deserve credit where credit is due, sorry if you got a bit ruffled.
Im at a loss to understand how running two fuel lines would work. Where is the air coming from to displace the fuel being consumed. Is it the vapor from the fuel being agitated thats the "air". Im not disputing the fact that it works with just two lines, just at a loss as to how it works.


Johan

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11-11-2005 01:08 PM  12 years agoPost 31
torque

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bolivia , north carolina

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CoastalTom
Status: Senior Heliman

Registered: Jun 2004
Location: Foley, AL (7 miles N of Orange Beach) I run my gasser with only 2 lines as you described and my engine has the primer bulb. No problems. I do disconnect both lines to fill the tank.

Tommy Patterson - Gulf Coast Aerials


here is his post. i PM'ed him and says that it runs just fine down to empty.

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11-11-2005 03:02 PM  12 years agoPost 32
CoastalTom

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Foley, AL (7 miles N of Gulf Shores/Orange Beach)

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Hey Guys,

I have been running a 2 line tank system on my JR gasser for about 3 gallons now. After "torque" pm'd me about it, I dug out the assembly manual and discovered mine is NOT plumbed as they describe. I bought the heli "almost" new with only 3 tanks run through the G23. It was set-up this way when I got it so I never bothered to change anything. Bill Meador is a long time friend and I took the heli over to Bill's to get him to help with tuning after changing carbs. We never noticed the "only 2 line thing" and he commented on how well it was running.

The manual shows the vent line on the tank top NOT being connected to the carb overflow. Mine, however IS connected. Pick-up fuel line of course connected to fuel inlet on carb. Manual shows a separate piece of line comming off the return nipple and turning straight down below the engine.

All I can say is that it runs well with only 2 lines (both connected to carb). This is my aerial photography platform with stretched boom, 800 mm blades and 9.0? gearing. Minimum vibration so not much fuel foaming. There is a check valve ball next to the overflow return nipple. Maybe air enters there?

I'm gonna call Bill and discuss!

Tommy Patterson - Gulf Coast Aerials

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11-11-2005 03:05 PM  12 years agoPost 33
AceBird

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Utica, NY USA

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QUOTE>>>

acebird
i just spoke to "coastalTom" and he said that he run only 2 fuel line, no vent line, and has no problem. he said it pulls the fuel until empty.

END QUOTE>>>

Sure it will torque. The pump is very powerful on these carbs. That’s not the issue. The issue is the variation you will get in the metering (air to fuel ratio). Perception is a very bad human trait. Once the brain convinces itself that it is doing something right it is very hard to retrain the cells.

Your tank is going from positive pressure to negative pressure as it gets empty. Don’t you notice the inrush of air when you remove the first tube upon refueling? Have you ever tried to restart the engine after a 20 minute run without refueling? It might be a little stubborn with just a little fuel left in the tank and the tank being at a slight vacuum. You may have developed air leaks around those bulk head fittings or elsewhere because of this positive / negative cycling of the tank pressure.

Look, if you only want two connections to the tank, cut the return line and add a “Y” fitting between the tank and the carb. On the open end of the “Y” reduce the tubing down for a few inches and point it up above the tank. If you ever use the squeeze bulb you can put your finger over the vent if you even have to. More than likely the excess fuel will go into the tank because it is the path of least resistance. At least this will save you from having to pull off one extra hose when refueling. Personally I don’t like taking hoses off from barbs, especially the supply line. It is only a matter of time before you start having air leaks.

Please look in my gallery (it’s a pain inserting pics into these posts) at the pic where you can see the tubes coming out of my tank. I reduced the vent line with a small black hose and go over the top of the tank and down to the skid on the other side. The black tube just fits inside the yellow tubing with no clamping necessary.

Pre-mix,

Sorry if I seemed ruffled, I am more concerned about my writing ability. My technical ability far surpasses my communication skills. As my post suggest (I think), not venting the tank is a bad idea. Your air to fuel ratio will be slightly richer when the tank is positive due to vapor pressure and slightly leaner when the tank is negative (near empty after a long run).

Ace

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11-11-2005 08:43 PM  12 years agoPost 34
torque

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bolivia , north carolina

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its back
acebird,

last night i put a new 603 carb on my xcell. the first couple of tanks went fine. then the last 2 tanks the primer bulb emptied out. almost to the point of being dry, but had just a few drops in it. i have been battling a gyro problem, thats why all the hovering. then the primer bulb prob. not sure what to do with the primer bulb problem. would the insulation block be a source?

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11-11-2005 11:39 PM  12 years agoPost 35
CoastalTom

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Foley, AL (7 miles N of Gulf Shores/Orange Beach)

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Ace,

You bring up some very valid points. I have re-started my engine after 15-20 mins run time with no problems and not removing any fuel lines. Obviously air is getting into the tank from somewhere but I have also felt the suction into the tank sometimes when removing the lines to fuel. I hate to mess with something that is working but I believe I'll try leaving the vent line open as described and see how it goes.

Is this an example of ignorance being bliss!

Tommy Patterson - Gulf Coast Aerials

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03-13-2006 12:21 AM  12 years agoPost 36
Kona Chopper

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Kailua-Kona, Hawaii USA

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I am having similar issues with me G230PUH with a wt603 carb. The primer bulb goes empty after 4-5 minutes of hovering. I've read this post and many others and followed the suggestions. I checked and replaced my clunk line. My clunk is equiped with a Stens filtered clunk. I checked to make sure my atmosphric line was unobstucted. Also checked my fuel return line. All ok. I took the carb out and checked and cleaned the little screen. The engine has a new phenoic spacer, gaskets, cylinder head jug, piston, and ring. I am in the process of breakin in the engine .I ended up plugging the fuel return line as some you suggest to daignose the carb. The fuel stays at the same full level in the bubble with the line plugged. Which makes me believe its a carb issue. The engine runs good with the fuel return line plugged. Should I just get a new carb or might it be something else. Engine temps are around 240 degrees. What about leaving the fuel return line plugged indefinately and just connecting it when I refuel at the beginning of the day. Would that cause any problems? I read from the posts that the return line is there just to prime the carb of fuel, that it.



Why buy?? when you can borrow and no return

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03-13-2006 01:04 AM  12 years agoPost 37
AceBird

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Utica, NY USA

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What about leaving the fuel return line plugged indefinately and just connecting it when I refuel at the beginning of the day. Would that cause any problems?
I almost hate to answer this as yes it should work although its a bit Rube Goldberg. It just kinda bugs me not getting to the bottom of this problem.

Ace

Ace
What could be more fun?

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03-14-2006 10:54 PM  12 years agoPost 38
torque

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bolivia , north carolina

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kona chopper
i was having a heck of a time with my prime bulb, then carey shirley mentioned that min. air sells a divider that goes between the carb and the spacer. he said that the temp from the engine sometimes affects the prime bulb. i took an old cd, cut it to fit and screw the top to the top frame with the shiney side out. it almost looks like a mirror and help viewing the prime bulb. the divider helps insulate the temp from the carb. i have flown maybe 7 tanks with this installed and so far so good. the bulb stays almost full. hope this helps

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03-17-2006 07:54 AM  12 years agoPost 39
Kona Chopper

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Kailua-Kona, Hawaii USA

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torque?
You know the part number to the "divider" that Min air sells? I have since flown 3 tanks fulls through my engine with the return line plugged. All flights have been flawless and without issues. I am still undecided as the whether to purchase a new WT-603 carb to see if the problem dissappears.



Why buy?? when you can borrow and no return

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03-17-2006 02:15 PM  12 years agoPost 40
torque

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bolivia , north carolina

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kona
sorry, i don't remember the min. part#. but its an easy fix. like i said, i used an old cd. one could also use a piece of cardboard. just mount it on the inside of the frame between the back of the carb and the engine. i also changed out carbs, thinking that was the problem, i went through the entire fuel system, but this has helped.

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