Sun Sep 25, 2011 9:16 pm
Hello all. It disturbs me to ask a dumb question like this but my 154 is running so rich that I can't stand to drive it. open the screw or close it down? It has a big NOS zenith on it. I have it open about 1.5 turns. It starts and runs good and seems to have plenty of power but it burns my eyes and stinks my clothes up real bad. Maybe the carb is too much. The timing and ignition system is not that old.
Sun Sep 25, 2011 10:12 pm
Could you be burning oil and or antifreeze? People cleaning main jets with torch cleaning tools ream them out bigger on IH carbs, I am not familiar with Zenith but imagine the same can happen.
Sun Sep 25, 2011 10:21 pm
The Zenith runs rich if it is the one with 5 screws holding the 2 halfs together
Mon Sep 26, 2011 7:58 am
If it is running that rich, it will cause other problems beside stink. Might have to jet it down a couple of sizes to work with your engine. Are you certain the choke is opening completely????? How about the air cleaner? Is it clean??? Both of these will cause the engine to run rich. If everything else is ok, try running it on e-85 for a couple of tanks. Might just run great.
Mon Sep 26, 2011 9:15 am
Garland, The "Idle Mixture" screw that you are talking about is an 'air bleed' screw for idle mixture 'air'. The system on the Zenith idle mixture works just the opposite of most carburetors. Most carburetor idle system screws adjust the gasoline in the idle mixture - the Zenith adjusts the air in the idle mixture. Turning the screw 'out' increases the air in the idle mixture and thus makes the idle mixture 'leaner'. The idle circuit really only affects the mixture at idle or about 500 to 600 RPM. Above that RPM the 'main mixture jet' starts to take over and the carburetor is running on the main mixture jet fully at any RPM above about 1,200 RPM.
The Zenith carburetor on the 184 came factory equipped with a #22 Main Jet and a #12 Idle jet. The 184 had a different Intake/Exhaust Manifold than the 154. To take advantage of the larger Zenith throttle plate, the 184 came with an intake manifold that was 3/4" internal diameter verse the smaller 154 intake manifold which was 5/8" (I think) diameter. If you have the smaller intake manifold, this might have an effect on how much vacuum can be pulled at the carburetor verses the venturi that is currently installed in the Zenith. In other words the vacuum signal that the carburetor is getting might be wrong.
I would first check what 'packrat' suggested; that the choke is opening fully and that the air cleaner is clean. "Wix Fleet" sells the air cleaner at a good discount (still expensive though). Then check for vacuum leaks with either propane or WD40. If all of that is good, then I would measure the internal diameter of the intake manifold and upgrade to the larger one - Hamilton Bob is a good source. If you decide to start playing with the main mixture jet, McDonald Carburetor in GA is a good source. I think that his main jets are about $10 plus shipping.
Hope that this helps, NJDale
Mon Sep 26, 2011 11:23 am
Great post, Dale. Somewhere I recall a post with information on Zenith jet sizes for service replacement cabs for the old IH carb. They were different than the late numbered tractors and Cubs that came with the larger manifolds and Zenith carbs as I recall.
Last edited by bob in CT on Wed Sep 28, 2011 5:18 am, edited 1 time in total.
Mon Sep 26, 2011 1:12 pm
Did something change or has there always been a smell?
Tue Sep 27, 2011 9:51 pm
Thanks basically it is all of these things. I think that the zenith is just too much carb. I may put the IH back on it. I replaced the filter and that helped, I adjusted the air screw out and that helped, I think I will shoot hamilton bob an email and inquire about a 184 manifold. Is a 184 manifold an integral unit like the 154? It looks like the exhaust and intake are integrated. I dread taking off the Muffler. MORE HEAT. The whole reason to change out the carb was because I needed more power. The zenith is a NOS NIB and I just put it on. I don't think it has been dinked with. That was several years ago and I haven't used the old tractor much. Most of the time has been spent on restoration. Thanks I will proceed with the sewing of the money!
Wed Sep 28, 2011 4:13 pm
Float level too high? I have zenith carbs on my fcub and one of my int154's and they run great. While repairing gravely tractors i found the venturi in the zenith carbs can be changed to smaller and larger sizes. Go to mcdonald carb & ignition on the net he has lots of parts for carbs.
Plus i said the ame thing this week while smelling my neighbors exhaust on his cadet this new gas smells very bad.
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