Box Stock

Clone ran practice fine then started to cut out.

G

GooseRacer

Member
As the title states last night It ran solid in practice. Then when heat time came around I got 4 or 5 good laps in then it's started to burble and sputter so I pulled off not wanting to hurt anything. Engine normally dies when choke is applied, this time I couldn't get it to die..it was idleing high and choke did pretty much nothing..
First thought was clogged jet. So I removed the idle screw, popped out the jet and cleaned liberally with brake clean. And reinstalled. Fired it and seemed to run ok on the stand with a normal idle and seem to rev ok..
Went out for feature and made one lap and it did the same thing again..
Am I hunting the wrong problem?
What am I missing..

Engine has about 45 laps since fresh this spring and was keeping up with the front in the heat till it started acting up
plug is 3910x(plug is also 45 laps old)
 
make sure your choke is functioning properly.
if it runs on full choke warm and climes rpm it aint the coil. id check all those stacks of gaskets and plates and make sure nothing has worked loose in the carb throat. good luck and let us know what you find out.
 
I have recently run into this too with a clone. Runs good about 10 laps then starts missing, sounding like its running out of fuel. After sitting a while, it starts and seems to run fine. Have changed the plug, put new carb and plate gaskets on (and yes I know how to install them properly) and again after 10 or so laps it starts missing. I haven't had much time to dig deeper into this although I have changed valve springs too. Guessing its a coil that is malfunctioning after it gets warm but haven't time to really test with other coils. I do know that once in a great while they do malfunction but if this is really my problem it's the first time its happened to me.
 
I was recently in a race and was moving up in the field at a pretty fair pace when the motor just Quit. no bang no pop no sputter just silence. pulled off pulled the cord several times. again, nothing. on the stand it fired up and reved fine. builder sent me new coil and fuel pump said to change the plug too. started to think the vent on the tank might have been the problem as I have one of those motocross ball valves on it. well see next race
 
I replaced everything no need in loosing money and a race hunting down 1 thing. Motor man said do it so I did
 
Make sure the carb is not coming loose from the head first… I would also check the small cap underneath where the fuel cutoff is could be loose or have picked up something from the tank or the bowl could be loose.
 
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