Ludwig: your question on March 25

Posted by RK Smith on April 15, 1999 at 17:40:00:

6 volt systems are notorious for hard starting. He stated his problem was "hard starting," which I interpreted as "slow starting," and he added that it ran fine after being pulled off. I would be curious to know if it then started o.k. with the starter when warm. That being the case, cold starting is more dependent than ever on fine tuning of the ignition and fuel systems. He said he checked the ignition, including timing, and substituted another starter, and secured the battery cables, and that the battery was o.k. - - all that seems to be left is consideration of the operation of the venturi system inside the carb, which is dependent on "proper" vacuum pressure and air/fuel mixtures at both the idle and main jets. Any obstructions in the carb could prevent the low idle venturi from operating when cold cranking, and "air leaks" in the carb from gaskets or worn throttle and choke shafts could reduce the negative pressure necessary to "carburate" the fuel. They can also change the mixture to a too-lean condition, which is exactly the opposite of what a cold engine wants. Pulling the tractor would spin the engine fast enough to activate the low idle venturi (even the main jet for that matter, if the choke was off) and with the throttle even half-open he would have quickly warmed the engine enough to sustain the output from the the main jet venturi. With the problems he defined, I would remove and completely disassemble and rebuilt the carb (about $30 if you do it yourself) and be particularly sure that no air leaks remained, and fine tune the idle jet needle valve at low idle "cold." This would be by cranking the engine cold on low idle, with the choke almost closed, and adjusting the idle jet needle valve for "reasonable running." It is possible then that even with the slow turning of the old 6 volt system, that the carb would propertly actuate the "low idle venturi." RKS

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