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Clooney
05-30-2002 03:46:37
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Re: Another Timing Question, Some Back Exhaust Tappet Noise in reply to 50man, 05-29-2002 19:43:12
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50man, fast idle [high idle] is 1375 RPM on a 50, with 1250 RPM being the working RPM. ~For timing setting purposes anything over 1000 RPM will give you full advance [if the distributor advance is working as it should]
~If you have the Wico dist., same settings only no advance.
~You didn't say if you have a gas burner or all-fuel? [20* BTDC for a gasser & 25* BTDC for an all-fueler]. I don't know about optimum timing as that depends on how you are using the tractor, but they seem to run pretty good at 20*- 25* BTDC. If you go much over 25* on a gasser it will hammer pretty good under heavy load.
As for the black smoke, that is normal [IF] you trying to idle the engine too low [if you are trying to idle it much below 500 RPM the carb metering will go rich & will need the idle mixture screws turned in to compensate, then put back for normal idle speeds]
~On valve adjustment, the valves are [mechanical lifters] & need a running clearance to keep from burning the valves, if you can't hear them, they are too tight. They must be adjusted hot, [not just run for a few minutes hot, but work it for a while hot]. Due to wear on the rocker arm shaft, rocker arm to valve stems & cam wear the best way to adjust valves on an old 2-cylinder is to not use a feeler gage, but just bring the flywheel to the proper place for the valve(s) being adjusted then turn the valve adjusting screw in until there is "0" lash [or until the rocker arm play is just gone] then back the adjuster out 1/3 of a turn [that is real close to .020�]. If a feeler gage is used & there is rocker arm wear, the feeler gage will bridge the wear area & the resulting setting will be too loose. On my personal tractors that call for a .020� settings I use a dial indicator & set the valve lash to .021� measured at the rocker arm, at a point just above the valve stem. Or if lazy just use the 1/3 turn out method. I was brought up with the saying that �if you can�t hear them they are probably burning�. ~Wih the extensive use of unleaded fuel, the valves will slowly recede into the seat under heavy loads & slowly close the gap up, then burn due to tight clearance��
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