redidbull 54 #1 Posted February 9, 2014 My 73 12HP has a weird starting problem. It takes a while of cranking and then when it catches it runs at like 100 RPM. If I leave it alone I can eventually give it more gas and it runs awesome. I leave it for about a minute or 2 before I touch the throttle. When I start it I give it about 1/4 throttle no choke. It starts this way in all seasons but after the initial start I can restart it no problem. Thanks. Jim Share this post Link to post Share on other sites
boovuc 1,090 #2 Posted February 9, 2014 If properly adjusted, you really need to choke that motor to start it. Doesn't matter if it 50 degrees or 50 below. It should require choking to start. I would ask you if you've had problems using a full choke when starting. As soon as it fires, move the choke down to half or quarter open and see if it doesn't run better while it warms up. It sounds like it is just lean! Share this post Link to post Share on other sites
redidbull 54 #3 Posted February 9, 2014 I will try to choke it and see what happens. I do believe the carb is out of adjustment somewhat because I took it apart and cleaned/rebuilt it. Which adjustment is for mixture on the carb? Thanks. Jim Share this post Link to post Share on other sites
Digger 66 3,477 #4 Posted February 9, 2014 If properly adjusted, you really need to choke that motor to start it. Doesn't matter if it 50 degrees or 50 below. It should require choking to start. Right on ! Share this post Link to post Share on other sites
rmaynard 14,926 #5 Posted February 10, 2014 Word of caution. The engine should never run for any length of time at only 100 RPM. The minimum (idle) RPM is about 1100. Lower than that and you will not be getting sufficient lubrication to critical parts of the engine. Share this post Link to post Share on other sites
boovuc 1,090 #6 Posted February 11, 2014 Unless you have a fixed jet carb which I doubt due to the age of your tractor, you have two mixture adjustments. The Walbro carb will have three screws total that adjust. One is the obvious Idle "Speed" Adjustment. High on the carb and near that idle speed adjustment is the Idle mixture screw. Lower on the carb just above the bowl is the main fuel mix. After you rebuilt the carb the initial adjustments on these screws should have been: Idle mixture is 2.5 turns out. Main Mixture is 2 turns out. Once the motor is warmed up, you can tweak the carb from there. Share this post Link to post Share on other sites
redidbull 54 #7 Posted February 11, 2014 Thanks. I will try that tomorrow. Jim Share this post Link to post Share on other sites
