48 cub carberator

[G Dorn]

I been trying to get my 48 cub from backfiring fo a month now.I think my carberator may be the problem.I purchasev3 carberators but none have the right size air intake bore mine is 1 1/2 id.I can not find a carberator that replaces the original
What part # do need for my 1948 cub? My engine # is 251341 tractor serial # is 23735.Any help would be appreciated

 

[grandpa Love]

I been trying to get my 48 cub from backfiring fo a month now.I think my carberator may be the problem.I purchasev3 carberators but none have the right size air intake bore mine is 1 1/2 id.I can not find a carberator that replaces the original
What part # do need for my 1948 cub? My engine # is 251341 tractor serial # is 23735.Any help would be appreciated

More than likely the carburetor intake is correct and your hose connecting it to the pipe is wrong. The later cubs (from the '70s ) used a zenith carb ,it has a larger intake. Yours should use an IH carb. Or this kipa replacement from Amazon. The backfiring sounds like a timing issue to me . Posting a couple pictures of the carb and tractor would help us troubleshoot.

 

[grandpa Love]

My video shows timing an H4 magneto but the process is exactly the same for your Cub's J4 magneto.

 

[G Dorn]

More than likely the carburetor intake is correct and your hose connecting it to the pipe is wrong. The later cubs (from the '70s ) used a zenith carb ,it has a larger intake. Yours should use an IH carb. Or this kipa replacement from Amazon. The backfiring sounds like a timing issue to me . Posting a couple pictures of the carb and tractor would help us troubleshoot.

I purchased the kipa carberator on June 10th. It had a 1 1/4 air intake my hose is 1 1/2 inch is there a hose that reduces from 1 1/2:to11/4 inch.As far as timming I made sure the number cylinder had the piston on top dead center on the compression stroke with the fly wheel at the arrow on the tractor other than that I don't no what else to do.I appreciate getting back to.me

 

[T.R.K.]

Check timing.
Are you sure your valves are sealing properly? A damaged intake valve or a bad valve seat will cause backfire back into the intake.
Also, is your intake manifold sealing to the head?
I'm guessing your '48 Cub has the timing pointer beside the front pulley. Have you put a timing light on it to see where your timing actually is?
(You can use a 12v timing light, you just have to power it with a 12v battery that is close by.)

 

[grandpa Love]

I purchased the kipa carberator on June 10th. It had a 1 1/4 air intake my hose is 1 1/2 inch is there a hose that reduces from 1 1/2:to11/4 inch.As far as timming I made sure the number cylinder had the piston on top dead center on the compression stroke with the fly wheel at the arrow on the tractor other than that I don't no what else to do.I appreciate getting back to.me

Should be able to buy a 3-4 inch piece of hose that goes on the metal pipe and the carb. Take both parts with you to Napa. Or just hose clamp it tight.

 

[G Dorn]

I just purchased a rubber coupling on Amazon 1 1/2 to1 1/4 inch and a steel coupler 11/2 for my existing hose.I appreciate your advice

 

[G Dorn]

Check timing.
Are you sure your valves are sealing properly? A damaged intake valve or a bad valve seat will cause backfire back into the intake.
Also, is your intake manifold sealing to the head?
I'm guessing your '48 Cub has the timing pointer beside the front pulley. Have you put a timing light on it to see where your timing actually is?
(You can use a 12v timing light, you just have to power it with a 12v battery that is close by.)

I checked the compression on my Farmall. All four cylinders register 120 so if I had a stuck valve or worn rings would I get that pressure.What should the compression be?also all plugs have a good spark

 

[47fivewindow]

Every Cub I remember back firing had the order mixed up. Clockwise rotation of the rotor looking at it from the cap side. 1342 counting from the radiator. I have heard of very old plug wires cross firing. A crack or carbon trace in the cap? Hope that helps

 

[G Dorn]

I changed the plugs and wires last year in May I have made sure the firing order is 1342 but I will double check again any suggestions are welcomed