My 20hp Briggs lawnmower hunts up and down and won't idle. It needs choke to keep running. It happened suddenly after I finished mowing one day. Is the carb shot?
KJ from Tulsa, OK
Hi you might want to pull the float bowl of the bottom of the carb and spray with a choke and carb cleaner. Remove the jet in carb also clean then blow them out with your air hose. Replace with fresh gas and go mowing. Something else I ran into awhile back that was way different the gas cap on our mowers have a vent built into them I had one that was actually clogged causing it to run on choke only.I'd do the carb first tho and blow out the vent just because.
If you left gas in your machine over the winter it could now look like jelly or varnish. So maybe the carb and gas line have to be cleaned. Also install a new spark plug or clean and regap the old one.
I always do maintenance on my machine so in the summer I just have to add fresh gas and it starts right up.
Also, if you have 10% ethanol in your gas and leave it over the winter the gas lines and carb will have to be cleaned. (05/08/2008)
I kind of had to laugh when I read your post. This sounds SO much like my hubby's JD, only his is an older model. He finally determined that the gas in his machine was stale. So he got an additive to mix in with fresh gasoline, and it cleans the carburetor. Hope this helps! (05/09/2008)