Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I pulled the carb off my ST824 to clean it out.  Just put it all back together and put it back on the machine.  I set the baseline adjustments to the idle and main mixture screws per the tecumseh HM80 service manual.  Adjusted the screws at high and low throttle settings like the manual states on got it running smooth at all throttle settings.  Problem is when I engage the impeller with the throttle full open the engine starts surging.  I'm new to playing with carburators, any ideas?

try this first!!!!have someone keep the impeller engaged while you slowly turn the main jet screw at the bottom of the float bowl counterclockwise.if it is just a bad adjustment and nothing plugged you will see the surging disappear. if it doesnt! mark the position of the floatbowl so it goes on the same way(scratch a line with an awl and index it to the carb base,the bowl position has to be correct for the float to work correctly.)  (important ).       remove the nut at the bottom of the float bowl,turn the main screw completely out of the nut and inspect the tiny holes in the side and bottom of the nut.use a small real fine wire to clean these holes up good.then spray with cleaner and compressed air to clean out.assemble bowl to carb with center nut and install the needle to initial setting,i would start with 1 1/2 or 2 turns out from completely in.once you have the initial setting put a load on the engine by engaging impeller and adjust to get rid of the surge.let me know how you turn out!! i have the same blower and did have the same problem as you describe.

Well it looks like the surging isn't the main problem.  The big problem is my auger drive belt is rubbing the bottom cover.  When trying to adjust the carburator under load like you described above smoke started pouring out from under the belt cover.  I just put a new belt in, it is the correct 1/2" wide 39.5" long belt that the parts manual lists, but it looks like it sits too high in the pulley causing it to rub the bottom cover.  The top surface of the belt is about 3/16" out of the pulley.  Did someone in the past maybe install the wrong pulley?  Looking at the belt I pulled off, it is only a 3/8" wide belt, not the correct 1/2" wide one.  I'm a bit confused.

if it is part #72086 it is 1/2" wide by 40" long and is for the attachment or impeller drive for series 924050 model st 824 blowers.the belt is correct but take the top plastic guard off in front of the chute and measure the idler pulley as well as the drive shaft and impeller pulley to see if the dimensional width's are the same if they are then check to see if the lower plate is not bent in and needs to be popped out to give adequate clearance for the belt. also make sure the belt tension is tight enough for the belt to ride in the groove correctly and both pulleys they are riding the same height.i believe mine also rides a little high in the groove.it would make no sense for someone to change pulley widths and go down in width,it would make the drive system weaker.   good luck! mike janesville wi.

Not familiar with this particular machine but if it uses similar belt guides as many other machines, it sounds like the belt guide fingers need to be pushed in a bit closer to the belt to bring the side of the belt in and the top down.

make sure the belt is routed correcty.  under brakes pads  NOT over them... under belt guides NOT over them....  i see this alot in the shop.  most of the time the blower housing should be removed to do a proper job for a novice....