[TR] TR4A carburetors woes

[Jeff]

I've been trying to get my TR4A on the road before winter sets in again.
I'm having a heck of a time getting my SU HS6 carburetors tuned.  I pulled
the floats and checked the fuel in the chamber.  They have Grose Jets in
them.  Both chambers have fuel about 1/2 way up the bowl.  I've done the
tuning on both carbs to where when you lift the piston the engine RPM seems
to rise and fall.  The engine runs great, I can rev it with no hesitation
and it seems very smooth.  I pulled the plugs and they were normal color.
When I take it for a spin though I can only get about 2 blocks and it starts
missing badly.  I get it home and pull the plugs and they are really sooty.
What am I missing?