Tecumseh HM100 10 HP starting /running problems

[dandonnell]

I have this older generator with the HM100 10HP engine that I am having issues with it starting/running. This is a used generator (1999) with very few hours I received for free because of the plastic fuel tank split issue on these Devilbiss 5250 generators. So i replaced tank and tried starting and it initially started well but the engine surged or hunted so I assumed it was carburetor since this unit sat for a few years with old gas. So I let it sit for a few more years and now i took carburetor off and cleaned out fairly well but didn't solve problem in fact now it is harder to start. So I ordered one of the aftermarket carbs on Amazon for $12 figuring what could I loose. That carb didn't work either so now it only would start quickly on choke but would either surge or stall out and not remain running. The carb wasn't exactly like the old so I thought let me rebuild the old carb with an OE Tecumseh kit. So got the kit and changed out emulsion tube seals, float valve seat and needle, bowl gasket and jet gasket. Float was plastic one with no leaks so I was able to re-use. Cleans all the main jet orifices and passages, made sure carb cleaner would spray through all passages under welch plugs but didn't remove them. When I tried to start with the old rebuilt carb it acted the exact same as the new aftermarket carb, would start on choke but would stall after a couple seconds. The only thing I haven't changed is the carb to manifold gasket although it looked good. Could I be getting enough of a leak there to cause this condition? I would think it would at least keep running with a leak but would run rough or erratic. Any other suggestion?

 

[Rivets]

Are you sure you set the float level correctly? I like to set them a bit rich. I think you are going in the right direction, as it sounds like a lean running condition, which could also be caused by a bad gasket. Please post the spec number for the engine, so I can see which carb you are dealing with. Those old tecumseh engines were work horses, still see a dozen or so every year, even though Tecumseh has been out of business for some time.

 

[dandonnell]

Thanks for your reply. The spec number for the engine is 159409P. I believe I found on the internet to set float level was to be set at 11/64ths from base of carb which is what I believe I set it to. How sensitive is this adjustment? If its off a little it can have the same symptoms I'm having? I haven't looked extensively yet but I would be nice to see a good cut away view of the carb and how the fuel/air flow operate through all the passages.

 

[Rivets]

11/64” is what the manual calls for, but based on my experience I set the Tecumseh carb floats so there is a drop of about 1/16-3/32” from the pin side to the free side of the float when tipped upside down. Not exact, just use my eye. This manual might be what you are looking for. Somewhere in my archives I’ve got one that color codes all the carb circuits, but I can’t find it this morning. Will keep looking. https://www.mymowerparts.com/pdf/Te...-TROUBLESHOOTING-AND-IDENTIFICATION-GUIDE.pdf

 

[dandonnell]

Thanks Rivets....I will pull it off again this Friday and check float level. Even though the carb to manifold gasket looks good I will RTV the surfaces to make sure I have a good seal. I know I played with the governor a bit when I did have it running somewhat while it was surging, is it possible that it could be so far out of adjustment that it wont continue to run? Maybe a dumb question..

 

[Rivets]

Simple answer, yes. Improper governor setting will lead to surging.

 

[dandonnell]

Simple answer, yes. Improper governor setting will lead to surging.

In my original post I mentioned that I haven't removed the welch plugs although I sprayed carb cleaner and seemed to be getting flow from under plug when I spray in other orifices of carb but could I be missing something important by not removing? I believe I have the new welch plugs in the new kit I purchased..

 

[Rivets]

Personally I normally don’t worry about welch plugs and seldom replace them. But I use an ultrasonic cleaner which will 99% of the time clean all the passage ways. Removing and replacing them I think is up to personal preference.

 

[Hammermechanicman]

Under the welch plug on the outside of the carb there are 2 holes that are atmospheric vents. You should not need to remove the plug.

 

[dandonnell]

Simple answer, yes. Improper governor setting will lead to surging.

Hi Rivets - I took off the original rebuilt carburetor and cleaned the welch plug on the inside and cleaned under the plug real good. Reseated the float bowl seal and emulsion tube again just to se if I missed anything and made sure all the passages were open. Didn't remove the exterior welch plug but I believe this is just a cover for some vents and when I spray carb cleaner inside the carb opening hole back toward the choke side and I get spray coming out of the three small vent holes in the carb body in front of the emulsion tube so all should be clear there. I also applied RTV on the intake carb gasket to make sure no air leaks there. As before the engine starts up immediately on choke but only runs for a few seconds and stops. I really think that it may be getting flooded as the spark plug is pretty wet when I pulled it after I tried to start a few times off choke. I then switched out the rebuilt original carb with the new China clone carb and it does the same thing, starts on first pull on choke and runs a few seconds then stops. Sometimes right after it may start on half choke but again dies after a couple seconds. The only thing I can say now I know since it starts easily on first pull is that the spark must be good and compression must be good. I pulled the plug after a few attempts at starting and the plug is wet like it is getting flooded. Maybe the float seal is not sealing good and flooding the carb but that would mean both the rebuilt original carb and the new China clone carb are doing the same thing as the engine acts the same with either one. Starting to get frustrated at this point. I really don't won't to go buy a new OE carb at $75+ . Any suggestions ?