spark plug fouling bas****
 

Ok....I bought this 95 FXD a few months back and it's now getting warm enough to enjoy it.
Here's the deal:
I bought it sight-unseen off the internet from a dealer in the South. It has a hypercharger and gutted out stock exhaust....about 25K.
I assumed it would run a bit rich here at 3500 ft so I've been reading all I can on forums and in the service manual but I'm not sure I'm doing it right.
My understanding is that you turn the idle mixture screw in until the engine starts to stumble and then back it out 1/8 to 1/4 turn? Right?

I started to town (15 miles) today and it was spitting and cutting out....I checked the plugs and the back one was carboned up really bad...went back home and jumped in the car...went to town and got new plugs...drove back home...put them in and drove on to town. It ran ok but I thought that I'd try to adjust the mixture. I turned the mixture screw in and there is little, or no, diffference...even all the way in...
What do you guys think? Smaller jets maybe?
Thanks for any advice and have a great weekend.

I'm gonna assume it's a stock carb (CV) and suggest turn it out 2 1/2 rounds and go ride it. Sometimes they won't stumble right away when you screw it in and sometimes it'll kill them immediately but it needs to be up to operating temp before even trying to adjust it that way.

If it spits and stumbles (running/taking off) after it's warmed up a bit, turn it out another 1/4 at a time till it stops doing it and if it takes more than 3 total, then a different jet might be the way to go.

Since we have no idea what jets it may have or what may have been done before you got it, try my suggestion, first chance you get, and get back to us...

PS Don't be afraid to use the enricher (choke knob) when it's cold, but only about half-out after it starts and it should do Ok pushed all the way in after about 3-4 miles in 65-70 degree weather. And a good idea to make sure the cable is letting it off too. With the knob pushed all the way in, you should see about 1/32" of the rod sticking out, as in - that's as far in as it will go.

Thanks man...I'll try that.

from my experience, if you can turn the idle mixture screw in all the way and it doesnt make any difference then your flooding, needle and seat sticking.

That's interesting. My bike has always been rather odd in the idle screw dept... I rejetted the carb to a 46 idle and 185 main - but it never stumbles even with the idle screw all the way in, or up to 2 1/2 turns out. never backfires, either. Any more than 2 1/2 turns out, and it's too rich - but I've never been able to make the engine stumble even with it all the way in. I practically rebuilt the carb when I rejetted - put in a Dynojet kit that replaced pretty much everything in there except the slide and rubber boot at the top. Plugs always stay a nice light tan, and it seems to run OK at just about any idle screw setting! Kinda weird...