Um problem

[Hunter65]

I have this Briggs and Stratton vertical engine that im putting on my go kart and when i try to start it it shoots flames out the carb where the air filter should be. Does anyone know why?

 

[frederic]

That usually happens with the spark occurs with the intake valve open.

 

[1992suburban]

valve trouble?
flooded?
out of time?

 

[Hunter65]

I dunno i havent opened it up and looked at it. How do i tell if timing is off and will flooding make it shoot the flames out of the carburetor.

 

[Rickracer]

Good possibility the flywheel key is sheared, causing the timing to be way off. That set of circumstances would cause what Frederic was referring to.

 

[Russ2251]

If haven't done so already...try a new non-resistor plug.

 

[Fawteen]

Rickracer has the most likely cause.

How's the compression? If compression is way down or non-existent, it MIGHT be a stuck intake valve, but the sheared key would be my first bet.

 

[Rickracer]

Actually Frederic had it, I just explained it.

 

[Hunter65]

The compression is extremely good actually. And where is the flywheel key?

 

[Fawteen]

The compression is extremely good actually. And where is the flywheel key?

Take the fan shroud off, then take the nut and washer off the end of the crankshaft that holds the flywheel on.

When you look at the area where the crankshaft goes through the flywheel, you should see a slot and a key which looks like a little piece of square stock, maybe 3/16 or 1/4 square. If it's sheared, you'll see that the slot in the flywheel and the slot in the crank don't line up.

You may have to pull the flywheel off the crank to be sure.

 

[frederic]

true, the timing could be off causing the intake valve to be open during spark.

It could also be a piece of carbonized junk stuck between the valve's skirt and the valve seat, keeping the valve open at all timse.

It could also be a chipped valve or a chipped/broken valve seat.

It could also be the valve stem is so rusty it binds in the valve guide preventing full closure.

It could also be a broken valve spring - remember that the springs close the valves and the cam lobes push against this force.

Remember that gasoline is in vapor form by the time it reaches the combustion chamber (or should be at least) and it doesn't take much of a gap for the flame front to find it's way past either valve and into whatever is combustionable behind it.

 

[frederic]

I guess I need to catch up before replying lol.

 

[theo]

Check the lifter to valve stem clearance, sometimes they are tight.

 

[Hunter65]

I just decided im just going to use a different 8 hp briggs with electric start hehe.