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Mike(NC) 
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Location: Asheboro, N.C.
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 Topic: Hard Starting "B"
Posted: 14 May 2012 at 6:46am |
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A question for the powers that B. I have a 1951 "B" that starts fair to good when it is cold. When you first crank it you need to pull the choke and release it as soon as it fires. After running it long enough to get it up to operating temp it is a pain to crank. Sometimes you can even run the battery almost down before it cranks again. I have converted it to 12 volts with an alternator but have left the 6 volt starter. These start attempts are short enough to keep from frying the starter. Also I have left the Fairbanks Morse magneto supplying spark thru the rotor and cap to the plugs. Is it possible for the coil or the condenser to break down enough for it not to crank hot. How costly is it to replace these parts. This site has been a great source of information in the past. The little "B" wouldn't be running without input from the great members on this forum. Thanks for any and all help, Mike
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Thank God for another day. Thank Him for being alive and all my many blessings.
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Nathan (SD)
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Joined: 11 Sep 2009
Location: Day County SD
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Posted: 14 May 2012 at 11:21am |
Does your tractor fire when you let off the starter?
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JimD
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Location: Mounds, OK
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Posted: 14 May 2012 at 11:44am |
Yup, sounds like the coil in the mag is getting weak. When that happens, pull a plug wire and compare the spark to the cold engine.
Also, check your valve lash. A warm engine may not let the valves close and so compression is much lower.
jimD
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j.w.freck
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Joined: 16 Sep 2009
Location: karnack texas
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Posted: 14 May 2012 at 9:34pm |
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you are right jim,i grew up with magnetos on the wc and the wd,s nothing like the battery ign.and a petronics mod from you...
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j.w.freck
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Posted: 14 May 2012 at 9:40pm |
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i might also add DO NOT use modern carbon spark plug wires or resistor plugs on a mag,it creates too much resistance for the mag and will destroy the secondary windings in the coil and will burn up points...
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CTuckerNWIL
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Location: NW Illinois
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Posted: 14 May 2012 at 9:49pm |
I think (and my wife tells me not to sometimes, or at least keep it to myself  ) that timing can be an issue when symptoms like yours appear. If the engine is up to temperature and you run it full throttle in 3rd and then back it off all the way, will it backfire once or twice? Some ole timers say it ain't right if it don't backfire twice.
Edited by CTuckerNWIL - 15 May 2012 at 6:51am
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Mike(NC)
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Posted: 15 May 2012 at 6:15am |
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Thanks for the input guys. I will check the wires but I think I put wire core ones on. The memory is not what it was and that build was 4 years ago. You are also correct about it starting as soon as you release the starter rod. I'll have to check the spark the next time we run it. My son usually drives the tractors because most of the time I'm not able to climb on them. Even with the step I put on it my wind is used up before I can mount it. I'll check all your suggestions next time we fire it up. Thanks again for all your help. I'll let you know the solution as soon as I can get it solved. Mike
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Thank God for another day. Thank Him for being alive and all my many blessings.
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CTuckerNWIL
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Posted: 15 May 2012 at 6:57am |
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Another possibility with the mag and having 12 volts, it might be turning over too fast for the impulse to work properly and if timing is just a tad advanced and the impulse is lacking, it can start real hard. I guess any time I have had timing and starting issues, it cranks over slower when hot. ??????????
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Nathan (SD)
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Posted: 15 May 2012 at 9:16am |
The reason I asked about letting off the starter? My expierience has been that most people do not have their throttle open enough to match the engine rpms as the starter spins it over. Most guys pull the throttle back to idle when they kill the engine. When the engine is warmed up it spins over way faster than when cold. When you let off the starter, the engine begins to coast to a stop. When the decreasing engine rpms match the throttle setting, it fires and runs.
Next time you are cranking the warm engine. Move your throttle ahead while you are cranking. If the engine fires, this will rule out a spark problem.
Edited by Nathan (SD) - 15 May 2012 at 9:18am
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