HW 5200 Backfires and Stumbles when starting

OK- now I swapped my HW 5200 back into my 250.
I bought a stovebolt adapter and now it is oriented float bowl forward, so now more dying on left hand turns.

Idles great. Picks up speed fast on the freeway when the 2nd barrel throttle plates open- you can feel it.

But on starting it backfires once. Then if I crank for 5 seconds it sputters then stumbles, and when the starter is off the car idles and drives fine.

This did not happen with my Carter RBS.

I have a DS2 with a flamethrower coil, new plugs, rotor, and cap. I think this is some sort of timing issue. I am runnng the vacuum line off a ported source and have about 8 degrees initial advance.

Any suggestions?

Thanks!

Just for kicks, try it on a full vacuum port and see what happens. If it is already on full vac try a timed port.

Your car really died on left hand turns? I thought that was for hard lefts.

Off the cuff, it sounds like too much initial timing.

You sure the balancer hasn't slipped?

Could also be a bad acc pump.

Your car really died on left hand turns? I thought that was for hard lefts.

Click to expand...

Every single time I turned left onto my street 1/4 mile from home my car gasped and stumbled. But only on my street and only on my way home. I think it had to to with the the fact that I was always going 20-25 MPH, braking slightly, and turning abrubtly . Most other left hand turns were fine. I could not fix it by raising the float. I "fixed" it by rotating the carb 90 degrees- now it gasps and stumbles (and backfires...) when I start it up!!!

H3 and Bort-
thanks for the suggestions.
By the way, here is the carb rotated to the proper position:

and also my shiny new Alum Rad from Oscar's on ebay...

Update:
Moved the timing from about 6-8 degrees to 14 degrees BTDC and it fires up much better. Not sure why the RBS didn't like initial advance more than 8 (too much pinging) but my 5200 won't start easily unless advanced more than 12-14 degrees.
Thanks for all the help so far.
Pics at:
http://homepage.mac.com/jaffes/cometcarb/PhotoAlbum31.html

Where do you have your vac advance hooked up?

If it was manifold on the RBS but Ported on the HW, that would explain it...

I just moved to SF. Where in the city are ya ?

Thanks Bort-
Both are ported vacuum sources.
I am tempted not to touch anything at the moment since it runs prettty well- just waiting to use a tank or two to check my MPG and look at my plugs.

Welcome to the SF Bay Area!
I live in Burlingame (made famous since it is the "B" in "BALCO" and the center of the steroid scandal...) and work in South San Francisco.

Right on. I lived in San Jose until last year, and took a year and a half detour to so-cal.

I played in a water polo tournament in Burlingame once. Nice place.

If you need a hand, let me know.