Carburetor replacement? IH or Zenith?

[Pfranck331]

OK I've had my 154 for a whole week now. Other than the day I test drove it and it never has run smoothly above idle, it backfires and blows Blacksmoke at full throttle. I have replaced the spark plugs with champion D21s, I have set the point gap .02" , I have adjusted the ignition timing to 16° before top dead center. While it is now running a little smoother and throttle operation is much nicer it still breaks up and smoke and backfires at full throttle.
I have been soaking the manifold Nuts for five days and today I pull the carburetor off, I will be replacing the manifold studs for sure , I want to check the valve clearance but my gaskets have not arrived.

My IH carburetor is pretty rough. The stanchion to bring to the base of the carburetor has flattened out in places for somebody took it out with a pair pliers the tube running into the venturing was about over and smashed on the End a bit, I rounded it out pretty good I think it's plenty open. I don't think it will restrict or not cause a problem just indication of poor maintanace.
I did check the fluid level before removing the carburetor and found it to be between the 5/8 & 9/16 inch from the top of the gasket time.( spirit level connected to the drain plug hole ). However upon disassemble I found that there have been two gaskets installed, closer examination so that the five screws have been doged down so tight that the top flange is pinched tight at the screws an ther is a 1/6" gap between the screws Were the flange was bent up by excess of gasket material.
Also look like the idle mixture screw was filed it was not concentric on the tip.
With the top half of this carburetor being warped so badly it's hard to tell if I have correct fuel level and even if I do, the bending may be affecting fuel transfer within the carburetor.
I had to use the two gaskets again and reassembling it.

Do you guys think this carburetor is causing my high rpm missing?

Should I replace this carburetor ? If so should I use the stock IH carburetor go with a Zenith.
Would staying with the IH carb make this more desirable down the road ?

If I go with a zenith what types of modifications should I be prepared to make ?
Does anybody offer a Zenith that has been set up specifically for the 154?

Thanks.

[Bob McCarty]

The top can be flattened. There are several "how to's" on making a jig, or you could send it someone who has a flattening jig and can do it for you. I'd suggest fixing what you have before buying a new one. It sounds like the damaged parts might be causing part of the problem. The backfire is a timing/ignition issue. Recheck plug wire order and timing.

Edit: Are you sure you have an IH carb now and not a Zenith?

[Pfranck331]

It has IH stamped on the side, so I am sure.
Plugs, points and the timing adjustments I made did seem to resolve the backfiring issue ,
I flattened out 95 % of the warping and used an economy rebuild kit , so the carb is in reasonably good shape now, only have about 2 hours in straightening it and $30.0 in parts.... Still stumbles at full throttle, seems better when it's hot, blows black smoke as is stumbles.
Replacement main jets for my 154 from Steiner are 0.035 "dia, I measureed my main jet and find it to be 0.040 "dia.
Under magnification I can see some very small burs I thing it was " cleaned " oversized?
So, do you think a new main jet is in order? Any one know where I might find a better deal than $14.95 & $7.00 shipping?
That knock off carb for $75.00 free shipping is looking better all the time!
I found this review in the " how to" forum. viewtopic.php?t=20230#p149115


viewtopic.php?t=20230#p149115
Thanks to Don McCombs

[Don McCombs]

That evaluation is NOT for the carburetors that are currently selling in the $75 range. That evaluation is for a USA made reproduction carburetor sold by TM Tractor Parts and Steiner (among others) that sells in the $250 range. Two entirely different animals, even though they look similar.

[Pfranck331]

Hi Don, thanks for the clarification. Do you think a new .035 " main jet would solve my problem?

Has anyone reviewed one of the cheep knock offs?
I defiantly plan on keeping the original... But if I could get a "working carb" to plow snow with keep the original for show.

If I can't get this one sorted out what would you recommend ?

[Don McCombs]

Did you adjust the float properly as a part of your carb work?

[Pfranck331]

I used a spirit level to check fuel level, it was 9/16" from the bottom of the gasket to the bottom of the meniscus.
I left the fitting a d tube installed (see above) to recheck after new parts were installed.
Why wouldn't I recheck it?

[Pfranck331]

Does anyone have an opinion on the main jet being my problem?
Does anybody have a source for jets at a better price?

[Bob McCarty]

Is your main concern the stumbling at full throttle now? Does the stumbling continue or is it just for a second or two? Did you readjust the linkage rod from the carb throttle shaft to the governor rockshaft? TM Tractor also sells jets, but I'm not sure that is your problem.

[Pfranck331]

It is Continuous, the last thing I did was adjust the governor to throttle linkage but I have not had a chance to run it up to temp since.
It starts at 10°F with no choke, runs really rough till warm ( I don’t expect more) and then runs good to 3/4 - 7/8 trottle when it starts cutting out & black smoke as governor opens throttle to 100%. Good fuel flow to carb carb screen is clean.

[staninlowerAL]

You did not say in the first post how you checked and adjusted the timing. Suggest using a timing light, check at low and high rpm. Black smoke could indicate insufficient air flow. Check the breather system including filter.

[Jim Becker]

. . . Replacement main jets for my 154 from Steiner are 0.035 "dia, I measureed my main jet and find it to be 0.040 "dia. . . .

Does anyone have an opinion on the main jet being my problem?

.035 to .040 adds about 30% to the cross section of the jet. It could be the problem.

[Pfranck331]

Stan, I used a timing light, checked fast and slow, I have installed new air cleaner.

Jim, exactly my thoughts.

All, this problem is almost completely resolved.
Ever tHing I have done has made it run a bit better, yesterday after running it up to temperature I readjusted the governor to carb linkage ( loosened another 1/2 turn),
While I had the carb lose I snugged up the gasket. When reinstalling the carb to the flange one of the bolts failed to tighten ( the aluminum threads had come out with the bolt).
One had been replaced wit a longer the original one is the one that would not grab I replaced it with a matching longer bolt. So now the longer bolts grab the last couple threads.( I guess I’ll be doing a thread repair on this carburetor soon I don’t think I want to double nut it.)
It was warm here 40 degrees+ and I had it running over 1/2 Half an hour , so I re adjusted the Idle air jet.
I changed the oil again, and ran it for 20 min or so. Smoke almost gone, stumbles only enough to irritate me, No worries about dying under a load anymore.

THANK YOU ALL,
Everyone who contributed to this thread.
I value experience and input.
I may yet try a new main .035” jet, or maybe solder over it and drill it to .035”.

[Bob McCarty]

The .040 jet is the correct size for a 154. Wouldn't changing to an .035 reduce fuel flow and more likely cause stumbling at full throttle? You might want to run some Seafoam in both the oil and gas and work the tractor hard (if you can).

[Landreo]

As Bob McCarty posted, the correct size is 0.040 for the main jet. Other causes of high speed stumble are poor timing advance, the holes on the side of the discharge nozzle are clogged, the accelerator well air bleed clogged, leaking at the float bowl gasket.