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Farmall 300 carb issues

T

tractorsam

Well-known Member
I am working on a Farmall 300 which I have had for a couple of years. Sometimes it works ok, other times not so much. It had been giving me issues again lately so I?ve given it some overdue TLC. It had electronic ignition and I?ve put a distributor (recent aftermarket replacement by the look of it) from another 300 in it. I set the timing by ear. I?ve adjusted the valves to 0.020? cold. I found the ignition resistor to be faulty (no idea how it was firing at all with that bad) and replaced it. I also got rid of the inline fuel filter and installed a new sediment bowl (which I?m battling leaks on). I also stripped and cleaned the carb. It now starts much better and pulls well but I get a lot of black smoke at idle. Removing the air intake pipe makes no difference, adjusting the idle air screw makes small differences but removing it entirely makes it idle great. I?m thinking I must still have a plugged passage somewhere? Is there anywhere sells a decent carb kit these days? Thanks, Sam
 

Check the float height, and also make sure the float valve is functioning. You probably do not need a carburetor rebuild kit. You need only a gasket set.
 
I did check the float height, (1-5/16? if memory
serves) but didn?t verify the float valve. I?m in need
of the packing for the load screw as it?s leaking. The
sediment bowl I put on is a new aftermarket (A&I)
and it seems to be leaking six ways from Sunday,
any suggestions? Thanks. Sam
 
I have a 300u-been in our family all my life-grew up operating it. Anyway, about 30yrs ago it got to running bad, and would foul the center 2 plugs. The engine had a loss of power, and sounded 'different', like it was starving for fuel. I had the carb off twice before I found the problem. There is a teeny, tiny passage in the carb that was blocked. It took me some time to get it cleared out, but that fixed my problem. That was 2000hrs ago, and has only needed plugs and points since then. It is still 6v and always starts in about 2 revolutions, all original 7700hrs. Mark.
 
Well first off i can guaranty the ing timing is OFF as what you may think is good it is not . Put a light on it and set to spec.'s , reset your valves because they are off . A hot valve set is anything over 70 degrees ambit air temp . Carb adjustment is best done with a warm engine and due to your ing timing being sofar advanced you are not going to get it . If the ideal speed it to high then you sucking off the main jet and not the ideal circuit . when i do a tune up on them i can get them to ideal down slow enough to darn near count the fan blades .
 
yep, as Vet says... "timing set to spec's" then you do the carb adjusting after points and timing is set. point settings change timing settings. carb settings done at a very slow idle. any ear timed engine is always too far advanced. people just keep advancing till the engine is smoothed right out , but its way too much.
 
I had a M that idled crappy for years, then I cleaned out the passage for the idle and then it purred. Same carb as 300. If it's smoking black your main jet prably needs to be turned in.
 
Found a timing light, will give it a whirl tonight. I will do the valves again after I cut down a feeler gauge. The rocker arms really need to be dressed. Thanks, Sam
 
Time with light at full throttle to 22 degrees before top dead center. If dist is in good condition, then the timing will retard to close to top dead center at low idle speed. If you try timing to top dead center at idle without making sure full advance is 22 at full throttle you will be no better off than you are now.

Carburetor is not the same as an M as it has different idle circuit. If it still smokes at low idle and not at higher speeds, most likely the idle jet inside (the long, skinny, jet with the tiny hole) is damaged or even missing.
 
The idle screw is an air bleed, if it runs better out, then it is getting too much fuel, I would suspect a float issue.
 
(quoted from post at 07:04:55 11/17/19) I did check the float height, (1-5/16? if memory
serves) but didn?t verify the float valve. I?m in need
of the packing for the load screw as it?s leaking. The
sediment bowl I put on is a new aftermarket (A&I)
and it seems to be leaking six ways from Sunday,
any suggestions? Thanks. Sam
Click to expand...

I have experience with those sediment bowl assemblies from A&I. You're better off to repair the original, or go to your local Case-IH dealer and get a sediment bowl assembly. The packing you need is also available from Case-IH.
 
There are 3 marks on my front pulley, two close together and one further away. I think the middle one is 22 degrees. At full throttle the timing is exactly on the 22 degree mark. At idle (which is still a little higher than I?d like) it is at about 10 degrees.

I replaced the idle jet as the kit came with a new one, although I had this issue with the previous one. Thanks, Sam
 
Good to know. Unfortunately despite 3 parts tractors
I don?t have a single original sediment bowl
assembly. Can a CIH dealer get a good quality bowl
(that is where the A&I bowl came from)?

I have another carburetor that I might try rebuilding
and put on, or maybe that will just introduce a whole
new set of issues. Either way, thanks for the heads
up on the A&I bowl. Sam
 
Do you have a carburetor number from the little round plate? If you have a 300 carburetor 361525R2 for gasoline turning the idle screw out gives it more fuel. Unless you have a different carburetor if you turned the idle fuel adjustment screw all the way in and still to much fuel at idle speed its pulling it from another problem in the carburetor or a tune problem. If you have a pulley with 3 notches the second one is 22 degrees. 4 notch pulley the third notch. Think you said something about changing the distributor? One installed with more advance than original and set to 22 degrees at full throttle will result in retarded time at idle.
 
First off, the little plate has the number 361525R91.

My pulley has 3 notches.

At high idle (full throttle, no load), the timing is at the second notch. At idle (throttle lever all the way down but still a bit faster than it could or should be) the timing is at about 10 degrees (roughly half way between the first and second marks). Thanks, Sam
 
363525R91 was used on early 300 gas. Originally they didn't have a load adjustment screw, just a plug that fit the packing nut threads. IH made enough change over kits back then with instructions to change tractors already sold to the 361525R92. Some 91 survived or have parts partly changed from rebuild kits so could be a problem if hard to find your problem. Most of those distributors needed the engine RPM to be down around 375 RPM before a time light check to TDC.
 
(quoted from post at 14:59:04 11/17/19) Good to know. Unfortunately despite 3 parts tractors
I don?t have a single original sediment bowl
assembly. Can a CIH dealer get a good quality bowl
(that is where the A&I bowl came from)?

I have another carburetor that I might try rebuilding
and put on, or maybe that will just introduce a whole
new set of issues. Either way, thanks for the heads
up on the A&I bowl. Sam
Click to expand...

Not too many years ago I bought a sediment bowl assembly from my Case-IH dealer. It was an original style, with IH part numbers. A dead ringer for the original, and was only slightly higher priced than the after market knockoffs.
 
I found my other carb (the tag isn?t great) and I think it?s a r92. I put it on today and after some adjustments it is working much better. Thanks, Sam
 
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