b717doc

Homelite 30 cc (Super II Viper chainsaw) engine, Carb will not draw fuel from tank....has a "reed" valve type thingy in the carb base plate....Should I see fuel being drawn from tank while flipping prop through? I primed the engine, and it did start by flipping, then fuel was present....Is this normal? Thanks.....

Rupurt

If it has fuel and it wont even pop i would check for a spark if there is a spark check the timing(if it sparks close to tdc it will at least pop). If the engine is new you may not be getting good enough compession to start it by hand so try an electric starter

Rupurt

Sorry i didnt read your question properly. You should be able to see fuel coming up the tube untill the air has passed through when the tube is full of fuel it will be difficult to see if it is flowing. Unless your tank is very small i think it would be difficult to see if the fuel is coming through by watching the level of the tank. When i choke my engine and filp it by hand i can see the fuel jump up the tube about an inch with each flip.

b717doc

Hey Rupert,,,,

Not happening,,,,,I get the fuel line halfway filled with fuel, connect it to the Walbro, open the throttle full open (or any other position), fully choke it, and nothing...the fuel is not moving at all. Tank is vented, and fuel flows out by gravity when disconnected....Maybe a bad diaphragm? The saw ran fine before I converted it...

av8tor1977

My Feedback: (6)

It won't pull fuel when you choke it and hand flip it unless the carb is really completely closed off. If the choke has a hole in it, as many do for starting with the pull start, you have to close it off, or use your finger.

Using your finger, make sure you have the carb securely closed off airtight, throttle wide open, and after several flips the fuel line should be full. When your finger gets a little wet, its ready to start. I usually take the choke out of the carb to improve airflow. I sometimes make a flat plat that pivots over the carb opening like a choke. Sometimes this plate, though it looks like it is securely covering the carb, will not seal well and I will have to put pressure on it to get a good choke. I've pretty much abandoned using these little plates, and just use my finger now.

Good luck,
AV8TOR

Rupurt

Ok. I have a choke with a hole in it and the fuel moves up the tube like said in post #3 the carb is second hand and came off a stihl brushcutter (i think), so the diaphragm must be really well used. Have you checked that the pulse hole lines up nicely and there is nothing blocking it.
aslo if you took it apart to see whats going on inside did you put it back together with the reeds on the right side of the gasket.(I trust you probably have, but you never know)

Rupurt

Or there is some dirt holding the inlet reed open wich could let it pump but when it stops pumping the lack of seal lets the fuel retreat to the tank faster than usual

Antique

My Feedback: (4)

Any Walbro in good condition will pump fuel 4 feet straight up..If the inlet needle is sticking or the pulse is leaking it will not...Take the cover off, the one with 4 screws..blow into the fuel inlet..If the inlet needle is leaking you have a problem It should not unseat unless you push the lever down...It take at least 10 lbs pressure to unseat it, you can't possibly blow that hard...Be sure the gasket is against the carb with the diaphragm on top when you put it back together...see that the pulse holes are not blocked or leaking in the block under the carb..
Choking by closing off the intake and fuel pumping after the engine is running are not related...Choking uses the upstroke of the piston to pull fuel from the tank through the inlet needle, pumping uses crankcase pulses to pull fuel into the chamber under the diaphragm, where intake through the carb siphons fuel from the chamber thorough holes regulated by the carb adjustment needles...

spyder0069

Ok, I am a newbie to gas engines and I just went through something similiar with my Ryobi 31cc. I tried plugging my exhaust and rotating the prop like my glow engines but that didn't pull any fuel from mine either. Since mines a rear carb and it was mounted to a test stand I couldn't get a finger in to choke it. Wouldn't start until I spun it with a electric starter. Then it ran great. My other question is since these come with a primer bulb is yours still connected? And if not did you remember to plug the outlet that went to the primer? I may be wrong but if that is left open I believe the engine just sucks air.

w8ye

My Feedback: (16)

The primer bulb generally has a check valve in it to prevent the sucking of air.

If there is no primer bulb in the circuit at all, you will need to plug the return line to keep it from sucking air. You will find out. The carb will never pump fuel if you don't. It doesn't work to stick a piece of fuel line on it and run the line into the tank. If the end of the line in the tank is ever uncovered by the fuel, the engine will stop or at least burp if its a momentary event.

Putting my finger over the muffler never did anything for priming the gas engine with a pumper type carb. A Ryobi with the Phelon ignition will not hand start anyway so I just use the elctric starter.

I've seen all kinds of choke set ups for these. I don't use any at all but some people use a rubber pad on the end of a pop stick. Others have devised ingenious slide schemes to choke the engine.

Enjoy,

Jim

b717doc

O.K, replaced prop hub that stripped during start attempts (the threaded shaft coming out of the flywheel is awful short), which my neighbor fabricated for me on his lathe, and fooled around with starting it again. Disassembled carb, everthing in order......manually primed Walbro with quite a bit of fuel, Prop hub came off again while using electric starter, striking right thumb and shearing wooden 18x10 wooden prop. No blood, just extreme pain, funny dancing, and colorful words....Installed another prop, engine will almost start by hand, Took chance on starter again, and engine fired and ran smooth at high power, but will not idle. Fuel is visible moving from tank now....Replaced intake manifold gasket....Idling beautifully, then just quit, and will not fire after several attempts of choking and priming. Seems to be lots of residual fuel on garage floor under engine,,,perhaps too rich? There is only one needle, and it is marked "L", and factory blocked hole adjacent to it marked "H". At high power, lots of sputtering. Adjusted "L" needle and smoothed out nicely. Will try to fly this weekend pending weather here in the ATL.

spyder0069

The prop hub comming off seems like a scary situation. Glad you got it running. I ran my Ryobi for the second time last night. This time I adjusted the coil so it was as close a possible to the magnents and installed the primer bulb inline. Started alot easier. In fact I was setting the low end and it was purring along and I killed the engine to see about hand starting now that the carb seemed to be set. One quick flip is all it took. I imagine this wouldn't have happened cold but it definately wouldn't have before I made the adjustments (I still have a sore arm to prove that). I bet as it breaks in it will be easier. Also I am running the suggested 32:1 (with a teaspoon more for good luck) oil ratio. I have heard of people running 40:1 which I suspect may also improve the possibility of a hand start since it has less oil. Is there any trick spark plugs for these engines? Like those split fires or some hotter plug?

Rupurt

Sounds like you are having fun. You may already know this but most people swap the carbs with the low needle only for one with both. According to the experts its difficult to get optimum performance when you are unable to control the high speed mix.

I also had problems with my prop hub coming off when using the electric starter. I haven't tried it but i have read loctite is a good idea.

b717doc

12-03.....Flew today, carb sux....can't adjust, replacing with ZAMA, see NEW HOMIE FOR FRANKENSTEIN thread.....

Rupurt

cool if its one off the homelite 25(7mm venturi) it might be a little small to reach the full potential of your engine, but it if it has both needle it will be a whole bunch easier to tune (Just watch now i have said that it wont work at all)

b717doc

UPDATE.....01-03-04

Replaced gasket on intake manifold/carb,,,,fuel seen bubbling around base,
40 minutes of flawless flight!!!! Using 18x10 prop. Air seal is crucial on these, made a HUGE difference.....

smallplanes

My Feedback: (3)

My prop hub kept coming off my poulan 46cc when had proping it. rcign1 told me to put red locktite on the threads and taper of the shaft and it has not come off since. Works great try it.



Thanks
smallplanes