Does anyone know what the intialadjustments are for a Zenith carb? I have aplain 76 shovel with drag pipes.Except for the Zenith and the pipes, whichwere on the bike when I bought it, everything else is stock.The plugs are sooty. There is a wisp of black smoke at an idle. The bike is a little rough at this point. I know don't let it idle. As soon as I roll up the throttle the smoke goes away.The engine responds well on the run. Thanks for any help.

 

The Zenith carb is a love hate thing. They either work real good, or real bad.
Is it a adjustable main model? If so, 1 1/2 turn out from bottom on the idle jet, and 3 1/2 turns out on the main. I forget what the float should be set at. With the float needle jet in place, I used to turn it upside down, and if the float was a little lower than level, it was good. Pretty sloppy specs. Get an S&S Super E. It's a Zenith on steroids!

 

My experience with Bendix/Zenith carbs is they always run a little rich. I had one on my pan and loved it because it was easier to kick start than other carbs I tried. I always carried extra plugs tho! I would just get a CV or S&S Super E carb. Better gas mileage and power will be the difference.....And easier to adjust and find jets for.

 

Its driving us nuts. My mechanic neighbor is beginning to doubt his sanity.

Runs great, starts easy, just won't idle. Cold or warm, I have to blip the
throttle at red lights, or hold it at a high idle, like 1500+ rpms or so. Higher than it should be.

Its on a 1977 Shovelhead. The sparkplugs look good, tan & dark tan. No white, no black. No significant backfires, maybe a very occaisional part-throttle pop.

Any suggestions anyone has, I would love to try. We have installed a rebuild kit and set the floats a couple times and adjusted the main jet to get the plugs looking good and running smooth.

One other thing, my girlfriend held the throttle one day to keep it running while I put on my gloves, and she got it to idle just fine, around 1k rpm. Go figure. I've tried, it won't work for me, and I ride the thing every day.

Thanks,
Erik

 

When you rebuilt the carb, did you confirm that the idle circuit passages are not blocked? I'm just guessing that the idle circuit is plugged.

 

Thanks MegaWatt, I did not personally check that but will relay to my buddy who did. He doesn't want to tear it apart again, but I think we're gonna hafta do that. They would be blocked with crud & varnish? Or by another part in the way. Sorry I just haven't spent enough quality time looking into this carb.

Happy Thanksgiving!!! I'm out til Monday.

 

MadSmokerBBQ,
Yeah, that's what I am thinking, varnish or some little piece of crud plugging things up. Hopefully, nobody has crunched the idle mixture adjustment screw down real hard and damaged it's seat. I don't know if that would block flow or create an situation where there is too much flow.

 

Ya know, I don't like calling wrenches about carb spec's, but I don't mind asking if I'm in the presence of a good wrench. I can set S and S's all day long. Simple, no problem. Often times ya bolt'em on and they work. You may have to twist the Idle Mixture screw out a half turn, mabey turn the pump screw out a turn to get rid of the pop. But they don't require any... Let me repeat this... ANY maintenence after you gett'em dialed in. This brand new Zenith, a shop convinced my friend to buy, had me yanking what grey hair I have left, out. Anyway... Thanks for the info, you've saved an ole iron head sportster from gett'in a round to put her out of her misery.