idles but can't throttle up

Porkman

New User
I have a "48 8N 6 volt, front mount. After mowing for about an hour last wknd backfired and ran really rough, no power. Was able to limp back to the barn. I have checked timing, changed points and condenser, cleaned air cleaner, opened up carb and it looked spotless so I did not do a full on cleaning. Found a small leak in manifold gasket and replaced the pair. Starts up and idles good but if I give it any throttle it sputters a lot and backfires some. Any suggestions?
 
Sounds like fuel supply. What happens if you choke it as you increase throttle. You have a mixture problem if that helps. You need a vented gas cap. You could be plugged up at sed bowl inside the tank. Fuel line blocked. Elbow fitting at carb plugged. Remove carb drain plug on bottom of carb you should have a steady flow of fuel when its removed. Make sure have the gas shut off at sed bowl open all the way. Post back if this does not help.
 
Drained the tank through the fuel line and first pint or 2 ran through ok, then started really slow down. I could visibly see that the fuel valve out of the tank couldn't keep up. Pulled the valve and the in tank filter looked clean. Blew out the valve w/ compressed air and reinstalled, didn't see anything really come out. Put gas in the tank and it is improved can get to about 3/4 throttle but backfires above that. Do I need more fuel in the tank to give me better pressure? Is there a certain amount of time I need to let it run to "work through it"? Only about a gallon in there right now, valve all the way open. Going for fuel now. Thanks for the advice. May be back for more ;)
 
After draining the tank and blowing out the fuel valve I'm able to get up to 1/2 with stable running. Choke just chokes it out as it would normally. It backfires worst when I try to rev it all the way open, about blew out my eardrum.
 
You should keep at least two or three gallons of gas in there and
only open the valve up about two full turns, not all the way open.

Opening it up all the way opens the "reserve" port at the bottom
which is often plugged full of dirt and/or rust.

I'm not sure that's your whole trouble though, since it quit while running.

Is the backfire through the carb or through the exhaust?
 
to clarify. I don't mean yank choke on full till handle pops off in your hand. I'm just talking feathering a lil choke.

still do it?
 
Yes, acts as choke should up to the point that it starts to stumble (about 1/2 - 3/4) at that point the choke doesn't seem to do much. With the improvement I saw after blowing out the fuel valve, I wonder if I need to adjust the timing. I had to move the timing plate to get the top right screw out when changing points this morning. Thought I had it back in the right spot. Would it idle well and run smooth up that far if timing was out?
 
Throught the exhaust. Ran out of light tonight. I'll make sure I've got 3 gal in there tomorrow and let you know what happens. I usually only run at 2 turns which is where it was when it started acting up.
 
Just loosened the screw on the left outside of the housing and turned the plate to remove the screw on the top right to remove the breaker points. After replacing I adjusted back as described in FO-4 manual. Used the same screw that was already there.
 
You said points replaced the gap is 15 not 25 on front mount, got the firing order 1243 and didn't cross up 3 and 4 it will still run but miss as you throttle up.
 
[b:18ae72ae32][i:18ae72ae32]FINALLY,....someone thought about the ELBOW SCREEN!!!!

Start checking there, and work back to the tank, for proper fuel flow!! higher throttle needs more fuel to the carb bowl!!!!!

Gary :shock: [/i:18ae72ae32][/b:18ae72ae32]
 

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