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JR Maley 
Silver Level
Joined: 21 Dec 2010
Location: Maryland
Points: 99
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 Topic: B runs rough when hot
Posted: 23 May 2011 at 6:07pm |
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I have a B that runs fine when cold, but when it warms up the transition from idle to full power is rough. It will pop and the governor will momentarily hunt for the correct rpm once up to speed. What should I try?
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Dick L
Orange Level
Joined: 12 Sep 2009
Location: Edon Ohio
Points: 5087
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Posted: 23 May 2011 at 6:46pm |
It is not getting enough fuel. Probably valves since it does not act that way until it warms up. I take it when you say (hot) you mean operating temperature.
If it is really hot then that problem would need to be taken care of before trying to solve this one. Solving the hot problem could solve the problem of not picking up the RPM's quickly.
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norm[ind]
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Joined: 29 Oct 2010
Location: bourbon,ind
Points: 2992
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Posted: 23 May 2011 at 8:12pm |
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is it a magneto or distributor ignition champion plugs will be irratic also
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CTuckerNWIL
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Joined: 11 Sep 2009
Location: NW Illinois
Points: 22824
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Posted: 23 May 2011 at 8:35pm |
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Check valve lash. I thought my 45 ran OK. I pulled the head off to mill the manifold seat and found the valves were sharp and pretty bad shape. After a valve job, I couldn't believe the difference in how it started and how snappy it was with the crack of the throttle.
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Dick L
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Joined: 12 Sep 2009
Location: Edon Ohio
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Posted: 24 May 2011 at 5:23am |
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Ya Norm, Its probly the Champion plugs. Just listen to this video to how bad the Champion plugs make an engine run.[TUBE]hM4YbM8keMM[/TUBE]
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Steve in NJ
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Joined: 12 Sep 2009
Location: Andover, NJ
Points: 11919
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Posted: 24 May 2011 at 7:38am |
As Dick mentioned, if you mean hot, as in normal operating temps I would lift the valve cover and adjust the valves as he suggested first. If it runs hot as in overheating hot, those little B motors usually run cool as a cucumber when the cooling system is in good shape, so if its running hot or overheating, there's a circulation problem such as a plugged radiator or murky engine or both. If its Mag fired, could be that little culprit of a condenser causing the problem, or if the Mag is equipped with the old style tar-taped coil yet, that also could be the problem once it gets to operating temps. The old tar-taped coils leaked and misfired causing the popping and rough running. Try the valves first... HTH
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Bill Long
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Joined: 12 Sep 2009
Location: Bel Air, MD
Points: 4556
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Posted: 24 May 2011 at 8:42am |
Listen carefully to what Steve says. That was out solution when the B's were relatively new. Condenser (cheap) and coil (more expensive).
Also, if the B has a tendency to run hot then it must be the radiator or clogged cooling system. Why, cause the B runs very cool. Hardly ever gets to the green area in the tempreature gage.
Take good care of my favorate.
Good Luck!
Bill Long
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JR Maley
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Joined: 21 Dec 2010
Location: Maryland
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Posted: 25 May 2011 at 4:16pm |
By hot I meant normal operating temp which is still relatively cool compared to most engines. I have a new condenser in the mag.
I'm thinking I'll adjust the valves first. I adjusted the valves a few weeks ago and the valve train was silent at first, but it started to make noise again leading me to believe I didn't tighten one or more of the lock nuts up enough.
-JR
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CTuckerNWIL
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Joined: 11 Sep 2009
Location: NW Illinois
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Posted: 25 May 2011 at 5:59pm |
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Did you adjust them at operating temperature? With solid lifters, there should always be a little clatter.
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Bob(W-Md)
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Joined: 12 Sep 2009
Location: Cumberland Md
Points: 86
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Posted: 25 May 2011 at 6:38pm |
Ok!!! This was the problem with my B.Would run fine until it would warm up.Then, when under load cutting grass it would start hunting bad.Not getting enough gas?? I first changed points & Con.It needed that.Still the same when under load.Then,I took the gas tank off to be sure no obstructions in fuel dilevery.Still same problem.Next, carb comes off for the 3rd time from previous tries last year and after a carb rebuild last year which I thought it was fixed. What I found was a piece of PIPE THREAD TAPE-I used to stop a fitting leak that got under the needle at the seat. Once removed, OK NOW!!To me the carb.would be the 1st place I would start unless you think there might be other issues. Hope this might help. They can drive you to drink!!! Bob
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