Phred;

Remember, you enrichen to choke (duh)...the SU is quite a bit different from typical down-draft carbs in that it(you) chokes by (manually)lowering the jet, and since the dashpot effectively is raised by flow through the carb (which during cranking is very low) it is down, and thus takes the place of the closed "choke flap" you may be used to from the down-draft carbs.

SUs also atomize pretty poorly at low temps, so the rule is to choke fully (jet 1/4" lowered), apply NO throttle (which would feed more air and undo the enrichening you need), and keep cranking (hopefully from a full battery with good voltage). The wet plugs you see are typical when choked and not started (no surprise there)...you'd be amazed how much fuel they want to start...charge your bat., pour a little fuel in each carb and try again (and NO THROTTLE this time)...you might be surprised! Let us know how you make out.

Please see also tech article on this very subject at: http://www.intelab.com/swem/checkchoke.htm

The "retard the timing trick" developed for super high compression engines might also help when its REALLY frigid and cranking is so slow that you can actually hear the cranking get hauled down to nothing when a cylinder firing occurs before TDC. Under normal running conditions, the flamefront in the cylinder takes some time to develop and make pressure so its OK to fire at 16 deg. BTDC, but when cranking dead slow, the flamefront actually beats the piston crown to the TDC and actually stops the cranking dead!...that's when it's time for some 5W-20 and/or a block heater and the retard trick. Usually, a good pre cold season ignition tune-up to assure that the everything is right on the firing side is a good idea too.

My list of things to check (any one of which will cause a no start in frigid conditions):

1. Are you getting full choke action AT THE CARBS?
2. Are all electrical (starting current) connections clean and solid?
3. Is ignition system in good state of tune?
4. Is thick (summer)oil or marginal battery or connections causing slow cranking?

Cheers, Ron