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Latest post Sun, Nov 22 2009 6:00 PM by hawgryder1. 10 replies.
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  • Sun, Nov 15 2009 9:03 PM

    1976 sportster with Zenith carb

     I recently bought a 76 sportster with a Zenith carb and cant seem to get it adjusted right. I start 2 turns out on both screws to start and go from there, is there somthing Iam not doing? Once a day it also will smoke real bad from the front cyl. then be ok, The smoke is a grey color and the plug for font cyl gets oil fouled about every 3 to 4 days ridding about 10 to 15 mi a day. Any help would be appreciated. Thank you

  • Sun, Nov 15 2009 9:44 PM In reply to

    • Ironhead
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    Re: 1976 sportster with Zenith carb

    finger - Don't know anything about the Zentih - on my '77 I replaced the Klein with a S&S E.  There are some on this forum that should know what you should look for, such as Xea, Fx, Sfrana, etc.

    As for the oil, it probably wouldn't hurt to get a compression test done on both cylinders - just to get a baseline.  Smoking every few days - I may be out to lunch but I am thinking a valve problem - maybe a bit of carbon under the exhaust valve or a valve guide sticking to the exhaust valve rather than a ring problem.

    hope this helps

    If a man speaks out in a forest and there is no woman arround, is he still wrong?  Geeked

  • Sun, Nov 15 2009 10:05 PM In reply to

    Re: 1976 sportster with Zenith carb

     I did a comp. ck not long ago and both cyl were good and the same in each. I was also thinking of valve guide problem but wanted another opinon. Thank you for your time, it will help alot

  • Mon, Nov 16 2009 5:00 AM In reply to

    • Ironhead
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    Re: 1976 sportster with Zenith carb

    not a problem

    as for the Zenith - I am sure Xea knows how to adjust it (he has forgotten more than most of us will ever know) - I beliefe FX and Sfrana should know about them as well - and I am sure there are others on the forum with experience with them

    have a good one 

    If a man speaks out in a forest and there is no woman arround, is he still wrong?  Geeked

  • Mon, Nov 16 2009 7:44 AM In reply to

    • FX
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    Re: 1976 sportster with Zenith carb

    Finger,

      Ironhead nailed it.......Valve guides. Oil in the rocker box is leaking down through the guides over night. When you say good compression, what are the numbers? Your engine would be good at 120, and no more than 8-10 difference between the cyls. 90-100 is borderline low, and could use a top end rebuild. If you're gonna pull the heads to repair, the cyls. are right there. Do the whole thing........The Bendix/Zenith is a pretty good carb, I'd start at 1 1/2 turns though. If the rest of the engine is not right, all the carb adjustment in the world won't make it run right.........Scott knows those carbs better than I do............Good luck..............

    FX

    Don't force it, get a bigger hammer.

  • Mon, Nov 16 2009 7:46 AM In reply to

    • rese81
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    Re: 1976 sportster with Zenith carb

     fingerofgo

    Ihave an 81 ironhead which has a bendix/zenith that had a similar problem. My scoot has 13/4" drag pipes no baffles,kept smoking up spark plugs,had to rejet!!!!! Go to the J&P catolog to see the jet sizes for the bendix,I had to use the smallest jet available to remedy the problem. You will have to rejet according to your exhaust and air cleaner Its easy to do bottom of bowl you will see a nut(9/16) which is actually the main jet loosen while holding bowl together remove and install new jet. Don't kill it when tightening!!!!!!! By the way fyi my carb has a fixed jet(non adjustable) Hope this helps. i was under the assumption that you were running to rich and smokin the plugs with gas.As far as oil fouling the boys know there bussiness

    RESE

    Lightning PEACE through belt fed weapons

  • Mon, Nov 16 2009 8:13 AM In reply to

    • FX
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    Re: 1976 sportster with Zenith carb

    The 'grey' smoke he's seeing is indicative (don't ask me how to spell that) of oil. If it was running too rich, the smoke would be black. The smoke is clearing up as he runs it, cause the excessive oil that leaked down from the rocker box over night is burning off. There is still oil leaking down as he drives it, and fouling plugs................Finger, The black deposits on the plugs would be shiney if oil fouled, powdery if fuel fouled, but black smoke, not grey..............

    FX

    Don't force it, get a bigger hammer.

  • Mon, Nov 16 2009 3:42 PM In reply to

    Re: 1976 sportster with Zenith carb

     My neighbor actually done the comp. ck while I made a beer run, he said both cyl. were 120 ea. Iam going to ck my valve guides and rejet my carb and thanks to all the good advice I should be on the road and running strong in no time. Thanks again

  • Mon, Nov 16 2009 3:54 PM In reply to

    Re: 1976 sportster with Zenith carb

     the plugs have been both ways and the smoke looks more like oil then gas, I guess I have 2 seperate problems. Thanks for all your imput I now have a place to start.I think you guys are great for shareing all your knowlege with the rest of us.

  • Tue, Nov 17 2009 9:33 AM In reply to

    • FX
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    Re: 1976 sportster with Zenith carb

    Finger,

     If the guides are bad (that I'm suspecting), replace them, and check into after market valve guide seals for the Ironhead. Do a complete valve job, and freshen up the cylinders while you're there. You'll have many many miles of trouble free riding.

    FX

    Don't force it, get a bigger hammer.

  • Sun, Nov 22 2009 6:00 PM In reply to

    Re: 1976 sportster with Zenith carb

     As you've been told...if the plug is getting oil fouled, you'll need to find the source.  But I wanted to speak more of your carb.  You mention "two" adjusting screws.  A fully stock Bendix carb has an adjustable low speed mix screw and a main jet.  However, if it's been converted to an "adjustable main jet" you will indeed have two adjustment screws on the top of the carb (along with the idle speed screw at the throttle cable linkage).

    Look close at the top of your carb....there will be a round adjusting screw with serrated edges (ridges around the outside edge of the screw head, like a dime) and a screw driver slot with a spring underneath it....that one will be the closest one to the intake manifold flange.  That is the low speed mixture.

    If that carb has an adjustable main jet kit installed...it will have another adjusting screw between the low speed mix screw and the air cleaner...this one will be HEX (6-sided) shaped, with a screwdriver slot in the top and a spring underneath it too.  If you have that style, it is an adjustable main jet. 

    As FX tells you...the LOW SPEED mix starting setpoint is 1 1/2" turns out from lightly seated.  That's the starting point...you set it there and let the engine warm up...then adjust for best running.  98% of all near stock engines will be fine between 1 1/2 and 1 3/4 turns out.

    The baseline setting for the adjustable main jet is 3 turns out from lightly seated.  Some of the kits sold today come with instructions that say 1 1/2 turns out, but I swear that something got lost in the translation when they started importing those kits from China, no joke.  Set it at 3 turns out....then ride it to dial it in.  You want to give it a full throttle run...the engine should accelerate and pull smoothly up through all gears.  If it's acting a little sluggish, turn it in 1/2 turn and try it again.  If it starts cutting out at the upper RPMs, turn it out 1/2 turn and try again.  Again, 98% of all near stock engines will do fine between 2 1/2 and 3 turns out.

    As far as the oil burning...you say "once a day it will smoke real bad, then be OK".  When is that "once a day"?  Is it upon start up after the engine has cooled down?  Does it smoke worse when you're accelerating...or is it puffing when you let off the throttle?  Even if your compression is good, it can still be oil getting past the rings.  Typically, if it's a guide the engine will puff smoke when you let off the throttle and when you're idling after the engine is warmed up....and rings will blow smoke when you accelerate/rev the engine.

    No matter...heads have to come off to check guides and as FX pointed out it's only four more nuts to check each cylinder.

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