KZ200 1979 / Aftermarket Carb Problems (Running Rich!)

Hi all,

Long time reader, reclusive poster.

I've got a '79 KZ200 rebuilt by the previous owner (engine) and myself (everything else).

When I got the bike, it had a Dellorto PHBL 26 Carb, which I replaced for a 26BS (jetted for Fantic 250).

Dellorto UK told me the new carb was suitable for 2 AND 4 strokes; turns out the bush was set up for a 2-stroke (sigh).

Fast forward to me trying to figure out why it's running so rich (!) now with the correct bushing (flat) installed in the carb.

I've reconfigured it to run on a Dellorto 110 Main and 38 Pilot jets (obviously those are the jets quoted in the manual for the Keihin PW26) and dialed her in according to Dellorto's specs (mixture screw, not air in this model).

But she's still carbon fouling the spark and I'm just not sure what the issue is.

The jets have been spec'd down (122 > 110 Main / 50 > 38 Pilot / left the choke as she starts without it).

Would changing the needle placement help? Lean it out a bit? I'm at sea level BTW.

If I lean out the mixture screw, I almost have to have the ideal screw all the way out (!) which obviously isn't good.

Any thoughts welcome!