Generic carb and fuel economy question
 

Hey guys. I'm trying to track down a rich running condition and excessive fuel consumption. It's actually on my Harley. The carb is a pretty simple setup with fixed main and idle jets. Only adjustment is a trim screw for the idle mixture, a fast idle adjust for the choke, and the idle speed adjustment.

The motor is basically stock with the exception of some drag pipes.

The Ironheads are known to get 40+mpg and right now I'm probably getting about 20 and my plugs are definitely black and a bit wet with fuel.

Can in improperly adjusted float level cause an overly rich condition and major fuel consumption? I know if it's set too low it can starve the carb....but it can work in the opposite direction as well and flood it right?

Only other thing I can think of is a bad set of jets.

I would think that if the jets were the right size then your float level may be too high. Or maybe a clogged vent?

I'm still thinking float level....however if the needle doesn't close there's an overflow tube that spills the extra gas out. I'm not getting that....but if it's too high but not reaching the overflow I suppose it's possible??

I checked the float level last night and it seems to be set properly. The jets are larger than stock and I'm wondering if that's my issue...they aren't huge though.

Main jet should be 160 stock and I have a 170 in....most guys go to a 165 anyway
Small jet should be 68 and this has a 74 in it.

Don't know if these are THAT much bigger to be running super rich and killing my fuel mileage.

Thoughts??

So apparently we've all forgotten how the old fuel mixers work around here with all the fancy fuel injection and such!

Anyway I swapped out to smaller jets last night and it definitely leaned out my mixture enough that the plugs aren't black anymore. Now my idle is a bit high and I can't back out the idle speed screw to correct it. I'm thinking maybe the mixture at idle is too lean now and causing it. I may get a jet between the two I've tried and see if it gets better. I also have a hesitation at about 1500 now that could also be from it being too lean. Balancing act I suppose.