4-stroke problem

[george kennie]

I'm having a difficult time with a brand new YS-63. Running Powermaster
YS-Blend 20/20, 12X6 APC, OS-F. It starts O.K., but when you advance the
throttle to full it takes about 20 seconds to slowly build up to max rpm
and then if you retard the throttle to anything below 8-9k rpm and leave
it there within approx. 5 seconds it will start to "splat, splat, splat"
and then abruptly quits, or if you try to advance the throttle it will
do the same thing and quit.After it quits, fuel will well up in the carb
bowl and overflow like the plunger in the regulator is not seating,
however I have inspected the regulator and the plunger silicon valve and
everything appears O.K.  I can even blow through the feed aperture in
the regulator and no air will go through it until I push on the plunger.
The are no burrs or any stickiness impeding the smooth operation of the
plunger and yet after a short run of a few seconds it acts like the
plunger is sticking in the depressed position.I've tried turning the
regulator screw as much as a couple of turns in as well as out and
nothing seems to help.
Anybody know why the regulator seems to be allowing fuel passage when
the engine isn't running? I compared the regulator spring length to a
brand new unit and it has the same length. There are no holes in the
diaphragm and the silicone valve seat appears smooth and does seat and
seal manually.
It will Idle, but as I recall that's a completely separate fuel
circuit.Is there something in the high speed carburetor circuit that
could be malfunctioning in such a way that pressure is getting back to
the top side of the plunger and holding it in the open position?
What do I do here, guys? Eric? Anyone?
Thanks guys,
Desperate Georgie

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