In order for the guys to offer advise you need to post a little background information such as
how was it running prior to this , what did the exhaust look like ? Was there any odd noises while it ran,
was it getting hard to start over time ? How was the power , was it missing etc.
The owner of the machine was having problems starting it, so he put a new coil, carb, plugs, and new head gasket on one cylinder, then he said it ran fine. The last two times he used it ,it was getting hard to start, then he brought it to me. i thought the float in the carb was stuck and know that aftermarket carbs can be at times unreliable ,so i put a carb from a manufacturer i use a lot and have had good results with, but i know now its not the carb.
The reason I ask for engine info is some spitting of gas back into the throat of a fast cranking small 4 cycle engine that won't start is normal thing on some engines and very misleading and cause one to get on the wrong page when trouble shooting the engine.
When seen the spit back is usually due to the compression release being on the intake valve/valves and when the carb throat/manifold is loaded up with gas it will spit some back gas the engine cranks fast.
Have a Briggs Vtwin 23 hp. that sheered a flywheel key. Replaced key, would not start, took brand new carb. off twice, reset armature clearance, reset valve lash. Would not start, kept back firing out of carb. Then it struck me, the beast is out of time.
