I have never seen this but here was the problem. The throttle shaft was broken not moving the throttle plate. I would start and run but not fast enough to deactive the compression release. Causing it blow back through the carb. Replaced The throttle shaft put the throttle plate back in. It cranked and ran fine. Thanks for all that posted.
StarTech
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There is always a first time...
I got one customer that has two throttle and one choke shaft. I could see a throttle shaft wearing in two but not a choke shaft, but I now know it can happen. All three were in twin barrel Nikki carbs on Kawasaki engines.
A cheap way to see into the cylinder is a bore scope camera that connects to a smart phone- they can be found online for about $25 and it's only 1/4", so it will fit into all kinds of close spaces.
How does that happen- throttle plate screw becoming loose and letting the plate shift & jam?
Seems like the first one actually wore in 2. The next 1 separated the throttle link plate on top of the shaft. The last one broke at the top throttle plate screw.
bertsmobile1
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Put your finger on the joint between the engine and the body
You are feeling for relative movement between the two indicating loose mounting screws
A loose motor will cause a knock at low revs that disappears at high revs .
You are feeling for relative movement between the two indicating loose mounting screws
A loose motor will cause a knock at low revs that disappears at high revs .