Starts, Runs fast, Then dies in 30sec

[Supernaut]

I didn't find a throttle disk anywhere around. By the initial behavior of my mower when the problem started it seems almost as if the throttle disk magically and suddenly disappeared. Now, thats not realistic. Never the less I need a throttle disk and I'm going to pick up a carb rebuild kit this week, set my governor according the the manual and hope that all goes well.

 

[Supernaut]

Well I have since replaced the throttle disk. Turns out the throttle shaft is broken so it doesn't fit into the little socket into the bottom. Never the less it holds the disk and appears functional by hand. I reassembled it all, set the governor according to the manual and tried to start. To make an annoying story short I can't get it to start at all. Not even close.

I did however find my old throttle disk. It was in the engine intake just past the carb. The little tabs that are supposed to hold it in look kind of flattened. Looks like it wasn't possible for it to actually get into the engine.

The last variable I can easily change I guess is the fuel mixture. I only see the one screw on there. Where abouts should that be positioned when starting from scratch?

 

[EngineMan]

D-400 Series - Turn carburetor adjusting knob counterclockwise two turns from seat to
make sure needle is open.

D-600 Series - Check atmospheric pressure adjustment - Correct normal setting is 1-1/2
turns from closed setting.

"F" Series - Check atmospheric pressure adjustment - Correct normal setting is 1/2
turn from closed setting.

"F" Series - Fuel flow needle valve adjustment - normal pre-setting is 2 turns from closed setting.

Check fuel line to see if fuel is flowing into carburetor.

 

[yabadabadoo1026]

re-starting this old thread cause I too am have issue with Lawnboy that runs strong and then stalls and dies----I can baby it at bit at the throttle to keep it going and then ultimately I cant any further and it dies. I have rebuilt the carb with the exception of the needle which looks just fine putting in new gaskets, making sure all holes/ports are clear. I did nothing with the float itself cause it looked good /did not check for proper height but it used to run good so sure the adjustment didn't change. Made sure the air hole in the fuel cap is clear, fuel filter is fine. Now I did have to put a new governor spring on it.

2 weeks ago was running strong after all the above but running too fast and that's when I started playing with the governor adjustment and now I'm back to it stalling out----------wouldn't suspect a governor adjustment could cause stalling. I have the 1 carb screw adjusted to best running.

This is making no sense to me----stalling suggest carb/ no gas ---fuel filter is clear and just not suspecting a float issue. It could be my imagination but thinking when its cold its running longer before stalling and then then when it heats up the stalling becomes more chronic. That might suggest something more electrical, right???????----------------haven't suspected spark plug or coil cause it runs strong when running before the stall. After the stall it will start back up so suspect the coil is OK.

I see one carb adjustment on this F engine with Walbro carb, Is there any other I've missed?????? In the 9/2 post by Engineman he is talking of 2 different adjustments on this F engine-----I see the screw on the outside of the carb in front , where is this other one referred to???????

Any suggestion appreciated------------if reliving this old thread gets no attention I'll post all this again in a new one

 

[LawnBoy4502]

Make sure to pull the black fiber liner inside the gas cap out and confirm no other debris is inside the cap. Mine did similar and the visual inspection was good until I took out the black fiber liner. It was apparently beginning to separate due to age and "throwing off" little pieces of debris that would clog the vent hole ON THE INSIDE - it was not visually a problem when viewed from the outside of the cap, either the top of the cap or the bottom of the cap.

 

[LawnBoy4502]

Any updates?