1250 Carb problems
 

Trying to get an old 1250 running. Put fresh gas in, took float bowl off and cleaned out the old varnished gas out. Cleaned carb out with carb cleaner. Will only start if I choke it with my hand (briefly close the throat) while cranking. This pulls up a huge gulp of fuel and the engine will run until that is gone and die unless I keep intermittently closing off the throat. I have set and reset the idle screws and nothing, it is just not getting enough fuel. Any ideas??

Sounds like you need to soak the carb and rebuild kit.

Have you done the obvious like make sure the tank valve is open? We had a 128 that was messed up and the valve wasn't opening. Another couple ideas would be are the hoses to the carb good condition? Sometimes they deteriorate from inside. Another idea is the tank valve was covered with gunk and fuel couldn't flow correctly..

Remove the main jet needle. It's straight down from the top, next to the throttle butterfly shaft.
Be careful removing it, it's long, and you don't want to bend it.
After you get it out, you will see there are several holes in it. There is one, sometimes two, at the bottom end, about 1/4" from the point. There are several others you should be able to see along the length.
Use a fine wire and poke any crud out of these holes and blow it out if you can with compressed air. Then put it back in, carefully bottom it, and back it out 1 and 1/2 turns. It should start enough to allow you to adjust it properly.

Oh, and Welcome to Only Cub Cadets!

Make sure you have flow from the tank to the carb, make sure you have flow from the hose THROUGH the needle valve and seat. Then try taking out the high speed needle as described in Rhoderman's post, not only do the holes in the needle need to be clear but the passage through the center of the needle, between the holes needs to be clear as well. Screw the high speed needle back in and then out 2 full turns, turn the idle mixture screw all the way in then back out 1 1/4 turns. Then try and see what happens.

If that doesn't do you any good then it's probably time for soaking and a rebuild.

Probably a good idea to check the throttle shaft and bore for wear while you're there, a worn shaft or bore won't keep it from running but if it's worn badly enough you will never get the carb adjusted so it will run well all the time.

D-Day: The advice about cleaning up the loong hi-speed main jet needle is generally correct. Except I would not ream it out or take a chance of bending it by sticking some kind of wires in there. That is what Carb Cleaner is for....

First soak all dis-assembled carburetor part in a gallon can of carb/parts cleaner (available from any auto parts store). Then, I just use a spritz-can carb cleaner (also from auto parts stores or Wal-Mart) on the hi-speed jet needle tube. There are three levels of holes in the tube. As stated there are two near the pointed tip (for the 1250 model carb). I use my finger to block one of them and put the red tube from the spritz can on the other....then spritz - and when I can get carb cleaner blowing out the other two levels (mid-way and up near the top at the threads), then I know the main jet tube is clean. Of course, you'll clean the end of your finger also, if you don't use something protective... This Main-Jet cleaning procedure will often work to get an engine running even when you don't clean the rest of the Carb!! BTDT...and I've got over 2 dozen running Cub Cadets for experience. And, I have found it is always good to remember as a field expedient when you are far away from the shop.

Myron B
CCSupplyRoom

Is your choke working? The reason it starts when you put your hand over the carb throat is that you are manually choking it. If it is cold and you take your hand off, it will stop running, unless you have it choked.

I had the same thing happening on my K341 recently, while I was just trying to find out if it would start at all (it had been sitting out in the woods for ages, had vines growing around it and mice living in the cooling shrouds). I got it running with my hand over the carb, then sprayed some PB "Tuneup-in-a-can" down the throat. Within a few seconds it was running at a good idle. That stuff is pretty good. I also used it on a 18 hp Briggs two-cyl that was "loping" after getting some bad gas and it straightened right up after two applications.

D-day,

I agree with Rhoderman about the wires. Mbounds has a point not to "ream" the holes and blast the holes with carb cleaner but I've found the wire in bread ties goes in easily. I use the bread ties that come with paper and just hold them over a lit match to burn the paper away. Any wire that's small enough will do. And I would use the wire on all openings, not just the needle valve. Just don't force anything. There are passageways and holes in the carb that can get clogged, or partially clogged and they can be hard to see. This is where the soaking is very handy. You may want to take the main jet seat out as well. It's located in the post that the bowl bolt screws in and requires a flat screwdriver. Be careful not to mess up the threads in that post with the screwdriver. If it's hard to break loose then you're back to soaking. It will come out but again, don't force anything. Be sure and use compressed air to blow out everything after cleaning and before reassembly.

Hope this helps....Wayne

I use the small string off a guitar.