Tecumseh 5HP Overspeed Problem

Old 12-02-07, 12:50 PM
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Tecumseh 5HP Overspeed Problem

Newbie here... I have an Ariens Snowblower from circa 1996, with a 5HP Tecumseh engine. The engine is an HSK600, 2 stroke, with float style carb (no diaphrams or idle adjustment screws). I recently rebuilt the carb since it was gummed up with varnish and wouldnt start. In fact gas was leaking into the exhaust and out onto the engine. After doing some reading here, I sent away for a rebuild kit #632760B. After blowing out the carb with carb cleaner, I replaced many of the internal components such as:

- Needle valve & seat
- New float valve shaft
- bowl gasket
- adjusted float
- welsh plug

Today, I put everything back together and into the snowblower and noticed the engine was difficult to start again when i pulled the rope. In fact the fuel began to come out the exhaust again (fuel/hydro lock i guess). The difference this time was the fact it was only a small amount. It did start though and after a few minutes of warming up seemed to run "ok" with a noticably high RPM. There was no surging either. I feathered the choke to control the engine speed but after 10 minutes of that, the rpm began to climb to very high levels and I shut it off. Restarting had no effect.

Anybody venture a guess as to what is going on??? I am confused at this point. Any help would be appreciated.

Old 12-02-07, 08:48 PM
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I have the same model engine on my snow blower. same carb, but I have yet to get it running, so I may have the solution, I just bought mine used, and it also had a varnished carb and a pinhole leak in the float.

it sounds like your engine is running too lean due to a partial blockage or a low fuel level in the bowl. also make sure if you replaced the welsh plug on the side of the carb, not the inside, that you sealed it with something that will not melt in gasoline, an air leak may make your carb lose its ability to draw fuel causing a lean air fuel mixture.

make sure there is absolutely no varnish inside of the hollow bolt that holds the float bowl on, as well as the small hole that is in the side of the same bolt as that is the main fuel metering port for the engine.

your engine might also need the float adjusted. if the tang on the float is bent up just an eighth of an inch, the engine will have a lower amount of fuel in the float bowl than it is suposed to have, causing it to run leaner. also

I am waiting for my new float. although your problem sounds different, check that yours is not full of fuel. when you shake it if it swishes, it needs replacing. trying to re solder or epoxy holes in floats, has not worked out for me yet. the float catches on fire, pops open because of the vapor inside when heated, or the epoxy melts in the fuel/ rattles loose and leaks.

do you have the part number list or diagram for the engine? I do not have part numbers / full part list for mine, and need it.
should have kept my old Tecumseh dealer part books.

so start with checking that the pinhole in the float bowl bolt is clear of any varnish, then smear a sealant over the bung is you replaced it (very sparingly) and test the motor. if the tang that pushes the fuel shut off pin into its seat is bent up to the point that the float does not close the fuel port when the float is level or just pointing up a little you can adjust that after checking to see if it was the blocked ports.

hard starting, overspeed, and choke compensation are all lean air fuel mixture indicators. also since this engine doesnt have any air fuel mixture needles due to newer EPA regulations, you cannot adjust the carburator to compensate for a partially blocked fuel port the way you could in the engines.
the newer engines, force you have to teardown and clean the whole carb to make the engine run propery every time it gets dirty / gummed.
good luck!
Old 12-02-07, 08:57 PM
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also double check throttle linkages.

[I have not messed with my carb much yet just pulled the float and discovered the reason why fuel was flooding into my engine as well. (leaky float) but make sure your throttle linkages are connected back up correctly. I have not checked to see if this engine is governed or not but the linkages are a common overspeed culprit on most small gas engines. (probably unlikely)
Old 12-02-07, 09:29 PM
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Sounds to me like either the throttle or governor linkage is not installed correctly, possibly the governor spring, or the governor arm setting has been changed. Did you loosen or remove the governor arm?

Lean fuel conditions on 4-stroke engines can increase RPM a little, but quickly becomes a surge rather than high rpm. I don't thin the fuel misxture is the problem here. It may need to be adjusted, but I wouldn't target that as the source of your problem.
Old 12-03-07, 04:18 AM
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Here is a link to the service manual for your series (as well as others) engine, this should help you get the linkages right. http://toprake.com/index.php?module=...position=11:11 You will refer to the 692508, manual. Also, I think you need to clean the carb better than with spray cleaner using a bath cleaner such as Napa's #6402. Strip the carb back down and soak the carb in this cleaner and also be sure to replace the emulsion tube (nozzle), which you have not yet, apparently. Without the specification number I can't supply you with the part number for this part, so post back with such number off the engine.

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