I have a tiller with the old flat head 5hp with the pull-choke type carb. It runs for a little while then dies and gas leaks out of the carb, think it is actually drizzling down the rivet that hold the pull choke in place. Engine model 13202, not sure if the carb is original or not.

The rivet is probably loose, but the gas that's coming out is because gas is being blown back into the throat of the carburetor. It's most likely caused by a valve issue, but it could also be a carburetor or ignition issue as well. I would check and see if it has spark when it dies, if so you may want to try opening up the adjustment on the carburetor a little to see if that makes any difference. If both of these suggestions fail to make a difference, then I would check the valve clearances and finally the valves and seats.

Best of Luck...

What do you mean check to see if it has spark when it dies? After it dies check for spark (I guess you are thinking that perhaps the coil quits after it gets warm?).

I had lapped the valves previously. I have played with the set screw on the carb, no improvement.

What do you mean check to see if it has spark when it dies? After it dies check for spark (I guess you are thinking that perhaps the coil quits after it gets warm?).

I had lapped the valves previously. I have played with the set screw on the carb, no improvement.

Did you reset the valve lash??

Reset valve lash.. does this mean I should file down the bottom of the valve stem. I did not do that. How do you know if the valve is making a good seal or not (with the head off)?

bump bump

The rivet is probably loose, but the gas that's coming out is because gas is being blown back into the throat of the carburetor. It's most likely caused by a valve issue, but it could also be a carburetor or ignition issue as well. I would check and see if it has spark when it dies, if so you may want to try opening up the adjustment on the carburetor a little to see if that makes any difference. If both of these suggestions fail to make a difference, then I would check the valve clearances and finally the valves and seats.

Best of Luck...

Were do you check for valve clearance?

Were do you check for valve clearance?

Just beneath where the carburetor mounts to the cylinder there is a plate that covers the valves, if you had the valves out to lap them, then you had this plate off. This is where the lifter pushes on the valve stem to operate the valves. The clearance is checked between the lifter and valve stem when the engine is 1/4" past TDC on the compression stroke.

Just beneath where the carburetor mounts to the cylinder there is a plate that covers the valves, if you had the valves out to lap them, then you had this plate off. This is where the lifter pushes on the valve stem to operate the valves. The clearance is checked between the lifter and valve stem when the engine is 1/4" past TDC on the compression stroke.


1/4 inch? Where am I measuring from?

you are measureing the space between the lifter AND the valve, with the motor at Top Dead Center, if they are closer than they should be, you need to remove the valves and VERY CAREFULLY grind them down, if you grind them to far, you will need to get new valves

you are measureing the space between the lifter AND the valve, with the motor at Top Dead Center, if they are closer than they should be, you need to remove the valves and VERY CAREFULLY grind them down, if you grind them to far, you will need to get new valves

I had thought that the valve stem and tappet were in contact at all times. You are telling me that at top dead center that the valve stem and tappet are NOT touching? Thanks, GoCart

I had thought that the valve stem and tappet were in contact at all times. You are telling me that at top dead center that the valve stem and tappet are NOT touching? Thanks, GoCart

That is correct, or at least they are not supposed to be touching. There should be some clearance so that the valves can close tight and give a good seal. You can find the settings specific to your engine with this chart.

http://www4.briggsandstratton.com/miscpdfs/RNT/Engine%20Specifications%20Chart_ms3992.pdf