'74 850 Norton with Mikuni wont run without enricher on

Wont run without enricher on. After I've gone around the block, starts acting too rich. But acts too lean when I switch enricher off! Stalled with enricher on and had to clear it with enricher off. Then only got it started again with enricher on. Is there a passage way plugged??

Joe Schlaberdowski said:

Wont run without enricher on. After I've gone around the block, starts acting too rich. But acts too lean when I switch enricher off! Stalled with enricher on and had to clear it with enricher off. Then only got it started again with enricher on. Is there a passage way plugged??

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Joe, I would first take off the top of the carb and pull the slide out to verify the needle is still secure in the middle notch,it can get dislodged
if that is still in place then unscrew the air screw and blow some compressed air in the hole, may have a plug, then set at 1 1/2 turns out
Then I would take off carb bottom bowl and check the tightness of the pilot jet with a small slotted screwdriver, it goes up into the body and can come loose

Thanks. Sometime tomorrow I'll have at all that. This was a bike I bought of unknown history. When I got it to start I was thrilled. Had one in '69, a Matchless Norton, but it was gone by '72. I've wanted a commando since then. Now I just have to sort out the inevitable things that are going to crop up.

Idle circuit is plugged. The small holes into the venturi is a good place to start.

Questions for both 1up3down and concours. I have about 100 psi and have a little nozzle. Will blasting that through the air screw hole unplug (of course if pluged) and how would I know one way or the other? That's about the same question for the set of three holes into the venturi. Or would I unplug and check with a wire?

Wire every passage. Verify flow using aerosol solvent (brake/carb cleaner) and watch for well formed round jets of liquid. Compressed air will not bust through a passage blocked with corrosion.

The 90+% issue is the idle jet. The passage that leads up to the pilot air trim screw and away can plug up, but that is relatively rare. Checking the needle is good counsel; give you an opportunity to see if the slide and/or the bore are worn.

Sounds like a good cleaning is in order; don't try to clean the idle jet, there are very few people that can do it properly and at $3.50/ea. it's just not worth the gamble.

You didn't say what year, but if your example has a fiberglass tank, your problems are just starting; if you have a metal tank be sure that it is clean.

Is the mounting rubber split or perished?