1982 Johnson 15HP tiller problems

I am working on a 1982 Johnson 15HP tiller and it runs fine up to just past half throttle and then it acts like its flooding out.It will run at full throttle but acts like its getting too much fuel, I tried to spray a touch of carb cleaner in the throat of the carb at full throttle and it dies out so I know it is naturally flooding.These are the things Ive tried to troubleshoot this motor,

1 leak down test and compression test
2 sprayed carb cleaner around the block to check for vaccum leak
3 It has new fuel and tank
4 put in a new carb kit(needle,seat,float bowl, etc)
5 did a spark gap test and it will jump spark great
6 did a coil test(using a coil tester) and they are fine
7 replaced plugs
8 tried slow speed screw to every position while running
9 check fuel pump that was ok along with fuel filter
10 checked flywheel for cracks ,flywheel looks excellent

It kind of acts like its out of time at full throttle but it seems to be a fuel related issue, any help is greatly appreciated in advance. I am leaning toward reed valves but I dont know how to check them without pulling the intake plate.

Re: 1982 Johnson 15HP tiller problems

check diaphram on fuel pump, a pin hole will let fuel in the the pulse port, and flood the motor. go to engine faq, read Joe Reeves carb adjustments. use pre mix gas to spray into the carb, carb cleaner strips the motor of lube. have you ever decarbed the motor?

Re: 1982 Johnson 15HP tiller problems

my thoughts are...

check the "link n' sych" between carb and timing plate... (check timing advance)
check spark/timing with a timing light (is it possible you're dropping a cyl at higher rpms?)

Also, look under the FAQ for a very good article on those motors if you haven't seen it already.

Good luck.