spasmatic

My Feedback: (4)

I too would like if Bob P. could expand on his conversion. If I understand it more I will be doing some conversions since my gas planes sometimes set for a few weeks between flights and take forever to get started again. I do leave them "wet" and gas in them but they are still difficult to start the first time. All my chain saws, leaf blowers, weed eaters, hedge trimmers are two cycle with primer bulbs and start easily every time. With a primer bulb it would not be necessary to pull the carb apart and squirt gas in it.

Bob Pastorello

My Feedback: (198)

spas - you describe exactly my scenario that got me to start this thread. Mind you, many will / may disagree and say such elaborate fixes are needless, etc., and there are folks who have their own way to address this. For *ME* - modding the carb to add a single-tubing primer bulb was a slam-dunk "do it once" kind of thing, so I figured why not?

I do apologize for the sketchy procedure and leaving out details and more pics. I'll correct those things asap.

microdon2

My Feedback: (47)

Bob - So you don't drill the larger bit all the way through so that the tube has a "seat"? I think I got that. I don't understand the primer bulb itself. Is it a pump that pulls gas from one side (the tank) and pushes it into the carb? If not, how eactly does it work? For mounting, just thinking you might be able to mount it underneath the cowl, just inside the air exit opening? Please send pics.

Seems to me that if this works so well Walbro (and others) should include it in their carb design. Seems like it would be a huge selling point, and I'd spend another $10 per carb for it!

Thanks.

w8ye

My Feedback: (16)

http://www.ebay.com/itm/2X-Snap-in-P...item43dac66419

one line to the new outlet in the side of the carburetor and the other goes back to the gas tank

On the bulb assembly, the long nipple connects to the carb and the short nipple returns to the tank.

Bob Pastorello

My Feedback: (198)

Probably that's the one that is smaller and easier, except for plumbing. Mine is a "single line", and it only connects to the carb. I don't know how it works, but it definitely does, and there is only ONE tube connecting anything. Clearly, mine is a vacumn bulb, as I can see the fuel drawn out of the tank line and it will drain out the exhaust when I've pushed it too many times. Pic coming...with link.

http://www.mfgsupply.com/20-10392.html

Bob Pastorello

My Feedback: (198)

Cowl with Primer bulb


Primer with quarter for size -

Lifer

My Feedback: (1)

I don't know if I'll ever use this option, but I do want to thank you for sharing! Very interesting.

microdon2

My Feedback: (47)

Bob - good pics. So do you press on the clear bulb or is it flexible plastic and you squeeze it? If there's only one line going into the carb then I'm guessing it must be shooting in air pressure, replacing the pulse of the engine (which we get by cranking \ flipping), and so then pulling in fuel from the tank. Since it takes only 2 or 3 pumps it sounds like it's also a stronger pulse. Sound right?

Bob Pastorello

My Feedback: (198)

It's a press bulb, and only takes about 3 or 4 "half pushes" to do the job. Squeezing it seems to make it leak slightly around the edge.
I think it provides vacumn in the fuel chamber under the diaphragm, imitation the pump diaphragm movement caused by the engine pulse, thus pulling fuel all the way up there.
Maybe someone with more knowledge of these one line bulbs could explain better?

w8ye

My Feedback: (16)

The old two line design draws fuel trough the carburetor and dumps the fuel (and air that comes along) back into the fuel tank. This model draws fuel through the carb and eliminates any air. This design puts no fuel into the engine. It just makes the carb ready to perform.

captinjohn

Take your pick...there is many. http://www.mfgsupply.com/smallengine...uelprimer.html

Bob Pastorello

My Feedback: (198)

Interesting. Mine is drawing fuel through the carb, because when I pump it too many times, gas flows out of the carb and drips onto the muffler.

Bob Pastorello

My Feedback: (198)

I've just finished modifying a couple of spare carbs. Testing them by attaching fuel inlet to spare tank outlet line, with Primer bulb on added tubing produced same results. About 3 half-presses, choke closed, throttle open just above high idle setting, and gas comes dripping out of venturi. This means that gas is being drawn all the way up to the metering needles for both L and H, and then into the venturi to mix for combustion.
If not for anyone else's benefit, this has been a good project of new discovery about some stuff that will make the intermittent flying of my gassers more enjoyable.
At least that's the hope, here....

w8ye

My Feedback: (16)

+1

acerc

I utilize the vent as Truckracer mentioned earlier. My vent lines are accessible from some point around the cowl. I use a small pump made for balls. With the needle broke off I insert the tip into the vent line and pressurize the diaphragm, then pull and actuate the pump. Doing this pump and vacuum a few times gets the pump diaphragm working easily and quickly.

Bob Pastorello

My Feedback: (198)

TR and acerc - I SURE would have preferred that method over mine, as it is the "easy" solution, and I am all about easy. EXCEPT...on ALL of mine, I've not plumbed the diaphragm vent someplace, because I've not had the symptoms of pressure build up in the cowl.
Having said that - on any future builds, or if I have to re-engine my current fleet, I'll sure look closely at doing the vent setup. NO doubt it is the easiest of all methods to get that diaphragm moving after being dry.

acerc

For me it was seeing a fella at the airfield with a little pump and wondering "What the hell is he doing", so I asked. At that time I had never had an issue and thought he was out of his mind. About two years later and having an airframe sit for nearly a year I learned the "What and why".
I do this for the carb, I have yet to have the negative pressure issue either and guess I never will now.

Bob Pastorello

My Feedback: (198)

+1 That is further evidence that RCers learn a LOT by watching others struggle. I've seen problems that should never have existed, but that didn't change the "cool" factor of the fix. Like putting clothespins on the aileron extensions hanging out of the fuse, so they don't vanish into the abyss of a dark fuselage, usually ONLY discovered when trying to assemble a plane at the field. Once I learned that little trick, the anxiety about "where are those extensions coming out at?" was forever solved.

captinjohn

+2

MTK

For rear carb set-ups, the carb will sit inside the soft iso mount's center hole. The firewall has a similar hole cut in its center area. The carb simply can't be sitting in a bubble in the cowl because the cowled area is vented into the fuse.

Of course this assumes one mounts the engines on a soft mount as I do. If you want to experience real noise reduction, try that. The softer the mount the better. Bobby knows this of course. I got the original design idea for soft mounts from his website many years ago. Now every gas powered plane I make from the 15cc powered T-Cup to the Yank54 for the BLE 55 has it's soft mount.

Lifer

My Feedback: (1)

Matt,

Can you give some details on the plane you call the T-Cup?

MTK

I keep forgetting that the T-Cup is my grandson's name for the T-Clip he got for his b'day. The T-Clip is one of the Sig arfies.....it's a short coupled cabin trainer type that comes out too nose heavy with anything other than about 6 ounces in the nose. My grandson's with the OSGT15 up front needed 12 ounces in the tail to balance.

I replaced the landing gear with a set I made from balsa, ply and carbon and removed about 6 ounces from the nose, so I hope that helps the flying and I can remove some of the dead weight (I abhor dead weight). The ground handling can be fixed with a longer tail which I haven't decided to tackle as yet. That's major surgery

I see I called it a Yank54 with BLE55....geesh. Yak54 with DLE55.

BTW fellas, anyone interested in building his own gas tanks from water bottles, I got the fittings. I also have the gas line that stays flexible inside or outside the tank, for years

Lifer

My Feedback: (1)

Thanks for the reply. I still have some of your tubing...it's the only thing to use inside the tank. Can you give more detail on the fittings?

MTK

Sure.... http://www.rcuniverse.com/forum/gas-...l#post11015010

BBBlue

Heres whats worked for me so far. No carb mods for the less skilled of us. Just forced fuel into the carb.
Choke on.
Pinch the ventline (plug the exit hole), connect the fueling probe and slowly crank the fuel pump a couple of turns.This will put pressure in the system. Flip the prop and 2-3 flips later U will see the fuel rush through the line to the carb. Put canopy on, unplug the ventline and proceed as usual.
Take care not to apply too much pressure in the system or U risk braking the fuel probe connection loose making a real mess!

Crude method one would argue but tested on two different DLE55s for the past three years with success.

Good luck and happy flying.