I bought a SMTA with a reportedly fresh motor and a carb problem. I went through the carb and I'm confident I found the problem, some kind of sticky thick gunk running down out of the manifold had the throttle plate practically stuck, plus there was some bug carcasses in passages here and there.
I soaked it and cleaned out all passages, etc, and put in new gaskets but I have to run the main jet adjustment in to about 1 turn off the seat to get the tractor to idle properly. Out any further and it's rich, and gets richer the more you back it out. Two turns out will kill the engine.
When the main jet is run in to idle good there is some activity in the idle mixture circuit, but I can't kill the engine with it, just make it rough.
I haven't measured the idle RPM's but it's nice and slow with the idle speed screw barely moving the throttle plate. I've adjusted the float level to about 1 7/16" with no effect.
Obviously the tractor won't work at high idle with the main jet screw in that far, and getting off the tractor to adjust the carb when changing throttle settings is too much exercise for me!
I should probably mention that the guy I bought the tractor from also has some M's built for pulling, and I wonder if this carb is modified for that? He had this engine overhauled 5 years ago, and the t/a, and had the sheet metal painted, but stopped on the project and never even started the engine until I went to look at the tractor a few weeks ago. I'm pretty sure that they were not particular about making sure this carb came off this tractor back when they disassembled the engine for overhaul.
Any ideas?
I soaked it and cleaned out all passages, etc, and put in new gaskets but I have to run the main jet adjustment in to about 1 turn off the seat to get the tractor to idle properly. Out any further and it's rich, and gets richer the more you back it out. Two turns out will kill the engine.
When the main jet is run in to idle good there is some activity in the idle mixture circuit, but I can't kill the engine with it, just make it rough.
I haven't measured the idle RPM's but it's nice and slow with the idle speed screw barely moving the throttle plate. I've adjusted the float level to about 1 7/16" with no effect.
Obviously the tractor won't work at high idle with the main jet screw in that far, and getting off the tractor to adjust the carb when changing throttle settings is too much exercise for me!
I should probably mention that the guy I bought the tractor from also has some M's built for pulling, and I wonder if this carb is modified for that? He had this engine overhauled 5 years ago, and the t/a, and had the sheet metal painted, but stopped on the project and never even started the engine until I went to look at the tractor a few weeks ago. I'm pretty sure that they were not particular about making sure this carb came off this tractor back when they disassembled the engine for overhaul.
Any ideas?