If you still have the surge after all that maintenance, you may need to re-jet the carb. You start with the low, and if that doesn't work, you go to the high. The easiest way to fix the low speed jet is to buy a bigger jet. The postage will cost more than the part. Look for prior threads for the part number.

I recently picked up a 10552 that surged wildly. I went to my parts and got a bigger jet. I unscrewed the old one and put the new one it is place, and the problem was solved. All without taking the carb off the machine.

You didn't say whether you added the fuel shut-off and extra fuel filter. This should be done as well.

I wouldn't be surprised if the stalling stopped after the re-jet, filter, and shut-off. I can't imagine that too much grass caused it to stall. You don't happen to be cutting 10 inch grass at the lowest setting?

htimsdj: No, my grass is only 3" max and I mulch it. Now, I understand the re-jet, but do you mean there is normally no fuel shut-off, so I should add one as well as an extra fuel filter. Are those simple to do and obvious once you have the parts? I just never looked at it that closely and got into repairs on it cause it never needed any til now.

The fuel filter and fuel shutoff are easy to do. You need a small fuel filter and a right angle fuel shutoff. You can get both parts from your local mower dealer.

There are pictures of the completed job somewhere on this site, but i can't find them.

Run about an inch of fuel line from the fuel tank to the inlet of the fuel shutoff. From the outlet of the fuel shutoff, run another inch of line. Then install the filter. Finally, run a length of fuel line from the outlet of the fuel filter to the inlet to the carb.

Thanks for all your help, I will let you know how it turns out. I have been checking all the posts on re-jetting, including drilling the current ones.

It does sound like it is starving for fuel. The tank has a plastic mesh screen in the bottom as a fuel filter which may have some trash clogging it, in addition the vent in the gas cap must be open to allow air to displace fuel being used. You could remove the gas line to check the fuel flow or just go ahead and remove the tank, shake the daylights out of it, dump the fuel and backflush the fuel outlet. I use a water flush for this as I am sure it is a "plastic safe" solvent, just make sure the tank is dry before refilling. If you can find some spray carb cleaner that is safe for plastics that would do a better job of cleaning but I have found a water blast to be satisfactory.

It is also possible the shop that did the carb rebuild got some trash in the screen that covers the main jet (another filter) or some trash in the float valve but I think you would get only 3 minutes of run time if this were the case.

I doubt if you need to enlarge the jets. It would have been doing that all along. They did something wrong when working on it. You may have over-torqued carb mount screws which could result in an air leak that gets worse when hot. Like already posted, it could just be the gas cap. Loosen it when it starts suging and see if it makes any difference.

Also might want to check to make sure the repairman didnt overtighten the carburetor mounting screws. If overtightened, it could cause an air leak. Also, check to make sure they used a new gasket between the carb and mount. Next time you have it running, spray carb cleaner or wd-40 around the carb and see if the engine responds to it in any way. If it does, you have a leak. 2-cycle engines are funny about leaks...they dont like them at all.

I did the gas cap thing when it first started acting up. Didn't help. I will check the carb mounting, cause I agree, it was fine before they worked on it this last time. Could the way it runs on full choke when hot, indicate an air leak due to improper carb mounting?

Yes, that is a prime sign that it is running too lean due to a leak. If it runs with the choke while hot, it is definately leaking somewhere. Do the wd-40 trick...i bet you will find where it is leaking.

Please help out there. I just picked up a friends Duraforce mower to help him get it running. It is a 10323 and I can tell by the surging and the leak at the bottom of the crankshaft, the seal must be leaking. Has anyone out there replaced the bottom seal. It is a self propel and I would like some guidance on this if a novice could handle this. Please give a complete walk through if anyone has done this repair. Thank you

The first thing you have to do is get the engine off the mower. The drive pulley must be removed because it won't fit through the opening in the mounting plate. Most likely the seal 'popped out' and is still in good condition. According to the book, the crankcase is supposed to be opened to properly replace or re-seat a seal, but I remember others posting on here that they did it without cracking the case. You can download the 'E' engine shop manual on the Lawn-Boy site which goes into detail. If the seal is only partially out, you may be able to re-seat it by using a seating tool (piece of pipe) over the crankshaft and pressing/hammering it back into place. This is why you have to get the engine off the mounting plate, to access the seal area, remove or replace a seal and to slip the tool down the crankshaft.

Thank you saxman. I will try that. I did search this foroum extensively on this issue and I did not see much on this topic. I would like to run another issue by you and anyone else for my issue. I have a 2002 10550. The low idle is fine. However, when you bring up increase the throttle it smokes excessively and I am using mobil 2t. I know the choke is not sticking because the engine begins to die whwn you push the throttle all the way up and it smokes even more. What would cause this? unbelievable smoke for a lean running machine and synthetic oil.

We'll use 'Occam's razor' on this problem. The engine is getting too much oil. Ta Daaa! Okay, that could mean you're putting too much oil in the gas or the carburetor is letting in too much fuel mix. Does the muffler spit black oily soot? Is your fuel fresh? Has the mower been exposed to water which may have entered the carburetor? You may just have a stuck inlet valve or a piece of trash in it. Get it running that way and pick up the back of the mower with the handle and drop it from about 6" a few times to see if it clears up.

Thanks again. I did rebuild the carb yesterday. Replaced needle and seat and cleaned everything else up. I am wondering if someone tried to enlarge the main jet and they over did it. I ordered a new one and will put this in. Gas is new and is mixed with Mobil 2t. Choke is not sticking. I think the main jet is my last avenue for the smoking Duraforce. Process of elimination? Any last thoughts before I put the carburetor back together after the new jet goes in. Carberetor was pretty clean. Thanks again Dave.

Just a follow up to my rich running (smoking) 10550. I took the carburetor off again to replace the main jet and there it was. The main jet that was in there was a lot bigger than the new main jet I just got. The owner before me had work done to it and the jet was drilled out so big I knew right away they went overboard on the jet size. I stayed with the 42.5 pilot jet and it started right up. A couple of clicks on the carburetor and this thing is running beautifully. I love this thing. Best find to date. All it needed was a new throttle cable, blade sharpening and a new 42.5 pilot jet and the non drilled main jet. Have to love it when a plan comes together. Thanks for the feed back saxman. I am loving the 10550 Duraforce.