A piece of dirt could be caught in between the float needle and seat,and or the float has a hole in it ,or the float is not adjusted correctly,or the atmospheric vent is plugged ,or the vicon seat was installed incorrectlty.... This is a typical fail on a tecumseh,you'll need to get back in the carb to check things out ,be sure the fuel tank is clean and the fuel filter is clean,if you have no filter you may want to install one.... Good Luck Jim

Okay Bill- I reread my post; not so clear...sorry. My question really is related to how low the idle rpm should be. The hi speed is good; smooth, etc. The low speed... well, I can't seem to make it as low as I have on other tecumseh horizontal engines. When I back out the screw for the idle speed where I have on other machines (by ear) I find the engine wants to quit. I'd really like to know what microfiche 30 says about the HM80 series. I was curious if my observation about the engine needing to run faster was related to the fact that it is constantly connected to the chipper disk/impeller. In other words; it's never really a "no-load." It runs well at around 3500 rpm; and it seems to run at a low of what must be 1500 to 2000 rpm.(My tach is AWOL this week.) I would have told you that this is about double what I have set oh, say my 6hp tiller engine (granted it's not the hm-80.) So; does that help? -br

Hello fellow surgers. I have a 1996 Craftsman 30" rear engine rider with a Tecumseh 13HP OHV engine. I had let this mower sit for 4-5 years, and went to fire it up. NO GO. So I just did a quick clean out of the bad gas deposits, and the mower fired up and ran, however it surged a couple hundred RPM throughout the entire throttle range and idle. So I cleaned it out again. Just with a can of carb/throttle body cleaner, thought I did a good job, it looked clean to my eye, but that was NOT good enough for it. But it still surged. I said the heck with it and used it for a year or so. I decided to tackle the surge problem again. With no short cuts. Now I was going to tackle it like the multiple hundreds of Toyota carbs I have rebuilt over the last 30+ years as a master tech, and not like a back yard quickie. Troubleshooting: Surging: throughout throttle range. Carb restriction. R+R (remove & replace) and D+A (disassemble & assemble) carburetor assembly. Pull out welch plugs and separate each & every piece from each other. I used: - 1) Factory Tecumseh-Power kit # 632760B - 1) 1 gal. Carb dip can with strainer from parts store. - 1) spray can throttle body cleaner. - compressed air (air in a can for cleaning computers can be used to check passages for flow along with the pressurized cleaners, if you do not have a compressor. - misc) small wires - basic hand tools ( screw drivers, wrenches etc. I used the end of a short socket extension to reinstall the welch plugs and sealing the external side welch plug with touch up paint.) It is best to soak the carburetor pieces in a dip tank for 24 - 48 hours to dissolve and soften ALL of the deposits. Agitated (plunge up & down in tank fluid) every few hours to flush fluid throughout pieces in dip tank Then I use compressed air and torch tip cleaners and or small gauge wires to clear out all passages in each affected piece. Re-cleaned with spray cleaner and thorough blow out everything again. CLEAN, CLEAN, CLEAN! It is critical to make sure the main fuel jet is cleared of all obstructions. NOTE: There is a very, very tiny orifice port in the fuel bowl retaining nut ( a hollowed out bolt with precise fuel ports that secures the bowl to the carb body ) between the 2 threaded areas, is a port called the "idle fuel transfer passage", this is a SURGING problem throughout the entire throttle range, from idle to WOT if this is plugged or minutely restricted. It also has 1 or 2 main fuel ports, depending on model, at the head end that must be CLEAN along with the center passageway. It is important not to accept a "half done" clean out and expect things to run perfect. That is what I did and I got SURGED! After I did a proper clean and rebuild of the carb, the mower runs like it did when it was new. I ran engine until warmed up to normal ops temp. and adjusted the idle mixture (only mix adjustment on my carb). I now have a nice smooth idle and smooth acceleration and WOT (wide open throttle) response. It is now PERRRfect!

The shaft Bill was talking about operates the throttle plate. Your governor link goes to it. Water damage is the worst to try and rectify. I would guess it had water in it and it froze also. Rebuilding it may get you where you want to go- or it may not. Corrosion doesn't clean out easily. Plus, if Bill's concern about the throttle shaft being worn in on, then the bore of the shaft may be also. You will see that the shaft will wobble -usually in a egg shape pattern. Hopefully the float and pin, needle and seat,& bowl seal are all the parts you need. If the bowl is questionable, replace it too and of course, the intake gaskets. Just visit your local Tecumseh dealer and all these parts will be in stock. And cheap enough too. If you do rebuild it, be sure the carb is upright when installing the needle on the side of the carb. There are tiny holes in the bowl nut to pay special attention to. Then check your governor adjustment. First, verify the links are in the proper holes. The governor arm should be all the way over as the throttle is wide open. The H and HM don't really make a difference. The HM if I recall is the new designation they made at the time. When I was in snow country, I had a chart of common snow king kits. Maybe your dealer does too. Good luck.