630 gas fuel shut off

Bret4207

Well-known Member
Neighbor has a 630 gas job. The fuel shut off has the thumb wheel and appears to have what I've been told was some sort of oil pressure activated shut off. Either way, it leaks fuel into the crankcase. Are these usually fixable by rebuilding the thumb wheel valve, or does it normally take a whole new assembly to fix it?
 
Normally the diaphragm has lost its coating.
Just replace it. It is a safety feature in case
there's a loss of oil pressure the gas shuts off.
 
If you get a quality ethanol resistant diaphragm, not one from Deere but one from a reputable carb repair place like Roberts you can fix it back up and it will last for years. I have replaced the diaphragm in the fuel shut off on my 630 twice in the past 60 years but I did not use dime store diaphragms. Another 630 in the neighborhood had the diaphragm replaced with one from Deere a few years ago, the Deere parts man swore up and down it was ethanol resistant and the very next year I was replacing that same diaphragm again. The deere diaphragm looked like it had turned into wrinkled tar. I replaced it with a diaphragm from Roberts. Like the other good carb repair places Roberts knows what quality is when they order carb parts. If you choose to replace the auto shutoff with a manual shutoff that's OK too. The auto shutoff is nice for guys like me who do not like to take the time to shut the fuel off manually.
 
www.greenpartsofva.com have diaphragms that resist ethanol. George is a great person to buy from.
 
"It is a safety feature in case there's a loss of oil pressure the gas shuts off."

You are correct - it will eventually shut itself off when it loses oil pressure, but not as quick as we would like. My old two bangers will run for several minutes on the fuel in the line and the float bowl if I forget to turn the fuel on. I can drive my 630 for 660 feet before it runs out of fuel when I forget to turn the fuel on. My hay storage area is a half quarter from the tractor shed. Several times I have stuck a bale and then ran out of fuel.
 
I have to plead negligence with this story, I did run my 630 low on oil one time and the fuel shutoff saved it. I was running wide open pulling hard running a brush hog. The valve cover gasket sprang a leak and I was tardy checking the oil so you know what the result was, out of oil. That next winter I had the first reduction cover off and while it was off I replaced the right hand crank main bearing. The old bearing was worn out of specs but the crank journal was still in specs but slightly egg shaped. All I can say is I got lucky.
 


Thanks guys, I didn't even know what JD called it to look for parts or posts. Now I can start looking.
 
The easy out is to put a SS ball valve after the sediment bowl. Good idea to repair the oil shutoff system, but they are prone to leakage. Didn't have an oil press. shutoff on my '60' but after 2 short time oil changes due to faulty sediment bowl shut-off and needle and seat, I installed ball valve. I hang a red plastic tag on it for memory sake , and hang it on the choke knob when in use. HTH
 

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