CUB WANT START help

730-LP · May 23, 2011

First let me say I am a Deere guy so I know very little about Farmall"s Here is the ?? I have a 51 cub that I have had that has gave me good service but last summer I was plowing potatoes and it popped and quit.What we have done. Removed front pulley & cover,every thing is in time,removed the head and replaced one valve that was bad,compression is now 90# on all cylinders,rebuilt carb,and replaced the magneto with one from a running tractor.We got fire but tractor will not start even if you spray carb cleaner in the carb.Any input would be appreciated

TheOldMan · May 23, 2011

(quoted from post at 06:03:44 05/23/11) First let me say I am a Deere guy so I know very little about Farmall"s Here is the ?? I have a 51 cub that I have had that has gave me good service but last summer I was plowing potatoes and it popped and quit.What we have done. Removed front pulley & cover,every thing is in time,removed the head and replaced one valve that was bad,compression is now 90# on all cylinders,rebuilt carb,and replaced the magneto with one from a running tractor.We got fire but tractor will not start even if you spray carb cleaner in the carb.Any input would be appreciated

Are you certain that the magneto is back in and timed to the engine properly? Sounds like it may be 180 degrees out. Also, what caused the bad valve? It only takes three things to make a properly timed and tuned engine run, spark, fuel, and air. Sounds like you have all three, so that only leaves two choices, timing and tuning. You have spark and rebuilt the carburetor, so the tune is probably good, and that leaves only timing. If you are not sure how to check the magneto for proper timing, just ask and I'll be glad to explain it.

TOM

El Toro · May 23, 2011

You need to bring No1 piston near the radiator to TDC on the compression stroke. Remove No1 sparkplug and hold your thumb over the plug hole while a helper hand cranks the engine until you feel compression against your thumb. You need to hold that thumb over the plug while the engine is slowly cranked. When there's no pressure against your thumb stop the cranking. No1 piston should be at TDC on the compression stroke.

Remove the cap and see where your rotor is pointing. It should be at the No1 plug tower on your cap that's near 1 o'clock. Here's the firing order for your plug wires on the cap. Hal

2-1
4-3 as the rotor rotates CW. You can have fire to your plugs even if the mag is not in time. The engine just won't start.

CUB WANT START help

730-LP

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TheOldMan

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El Toro

Well-known Member

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