Re: Ford 800 tractor runs great without Venturi!??
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Posted by samd on May 25, 1998 at 06:55:27:
In Reply to: Ford 800 tractor runs great without Venturi!?? posted by James Seabolt on May 21, 1998 at 20:21:41:
: The carb in question is a Marvel-Shueber .:
: My Father's 57 Ford 800 series tractor had been running like crap for awhile so I rebulit the carburator. Before it would smoke, foul plugs, die all of a sudden, wouldn't idle , was really loud ,etc.
CARB WAS RUNNING TOO RICH, RESTRICTED AIR INLET? WRONG FLOAT LEVEL? CLOGED PASAGEWAYS IN CARB BODY?
: After rebuilding the car, I set the adjustment screws one full turn out like the mediocre instructions that came with the rebuild kit said to. UNDERSTANDING PRINCIPALS OF OPERATION IS ESSENTIAL, MOST SHOP MANUALS HAVE A SECTION ON THIS, FIND AN OLD MOTORS MANUAL OR SMALL ENGINE REPAIR BOOK. ALL CARBS WORK ON THE SAME PRINCIPALS,,,,THE FUEL IS METERED BY THE AMOUNT OF VACUUM AND FLOW THE CARB IS EXPOSED TO : The tractor started right up. He ploughed with it all day. I didn't even make any adjustments to the carb! RISKY, IF CARB LOAD NEEEDLE IS SET TOO LEAN MELTDOWN MAY OCCUR!! : He said it ran great and ran tens times better than what it did before. : While he was doing this, I noticed I had left a piece out of the carb. I took this part to the tractor place and asked, "What is it and do I need it?" : They told me that it was the venturi and asked how the tractor mangaged to run without it. I said, I don't know but I do know it runs much better than what it did before. THE VENTURI IS JUST A RESTRICTION IN THE AIR STREAM THAT AUGMENTS THE RESTRICTION PROVIDED BY THE CARB. WE USED TO TAKE THE VENTURI OUT OF THE TINY SOLEX IN VW'S, IT GAVE A NICE SEAT OF THE PANTS BOOST : I was afraid to tear into the carb again, you know ,"if it ain't broke don't fix it". : So I went home, took the carb apart and installed the venturi. Afterwards the tractor sputtered and blew black smoke out the exhaust. I backed the screws all the way out but this did nothing. ENGINE IS RUNNING TOO RICH AGAIN, DID YOU SET THE FLOAT LEVEL TO SPEC? NEITHER MIXTURE SCREW SHOULD MORE THAN 2 TURNS OR SO OFF THE SEAT : So I took the venturi out again and now it runs fine. This time I did have to turn the idle mixture screw out about a 1/2 turn before the tractor smoothed out. AT 1 1/2 TO 2 1/2 TURNS OF THE IDLE NEEDLE, THE EXAUST SHOULD START TO BLOW BLACK SMOKE. TURNING IDLE NEEDLE INTO SEAT (GENTLY) SHOULD STALL MOTOR. YOU CAN'T SET THE LOAD NEEDLE UNLESS MOTOR IS UNDER LOAD : One thing that I have noticed is the fact that even when the tractor is warm, you still need to use the choke where as after the rebuild it would start "warm" without it. MOST OF THESE CARBS DON'T NEED MUCH CHOKE, MY 9N ONLY NEEDS ABOUT 2 REVS WITH THE CHOKE PULLED TO FIRE (UNLESS IT'S BELOW FREEZING) NEVER WITH A WARM MOTOR : This may be because I reused the gasket that goes between both halves and the intake to carb gasket. IT'S OK TO REUSE GASKETS IF THE'RE IN GOOD SHAPE, I WOULD RATHER GET A KIT, WAY EASIER AND BETTER IN THE LONG RUN : I assume this means the mixture may be a little too lean or it hasn't warmed up enough. MOTOR SHOULD START WARM WITHOUT CHOKE : Also there are three adjustment screws on the carb. One is called the idle mixture (fuel) , one is the air and one is called power. AIR???????? I GUESS YOU MEAN THROTTLE STOP WHICH SHOULD BE BENCH SET AT ABOUT 1/2 TURN FROM CLOSED : I know this sounds crazy but how do you set these things? I am a fuel injected man and deal with carbs very little (just the opposite from most people). : Also how come the tractor runs like crap with the venturi in the carb but will run great without it. AIR LEAKS IN INTAKE? CLOGGED AIR BLEED? PARTIALLY CLOGGED AIR FILTER? ALL GASKETS AND PIECES MUST BE INTACT AND CLEAN AND PROPERLY INSTALLED TO WORK RIGHT : Do I need to make new gaskets? GET A KIT : Also I didn't remove the power adjustment needle not knowing what it was. Should have read the instructions better. What does this thing do?
SUPPLYS EXTRA FUEL UNDER LOAD, VERY IMPORTANT!! SEE ABOVE
: Should I worry about having to use the choke to get the tractor started when warm? YES, THIS INDICATES CARB ISN'T SET UP RIGHT : Anybody out there that has worked on these tractors please get in touch with me because the IT shop manual I have isn't worth a crap when dealing with the carburators. : Thanks. THESE CARBS ARE VERY FORGIVING I'VE SEEN SOME THAT WERE WAY OFF AND STILL GAVE ADEQUATE SERVICE. HOPE THIS HELPS!!!!!!!! samd
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