Tecumseh quirks

[Mr Mower Man]

Hey guys,

I just wondered about something I had to do with a Tecumseh engine (OHH60-71105C). I replaced the carburetor, but it ran extremely lean when I started it up. Until it warmed up, it actually died several times. So I took the old bowl screw (with the main jet in it) out of the old carburetor, reamed out the main jet to about twice the size of the jet in the new carburetor, and used it instead of the new part. It runs much better now. It's on a Cub Cadet tiller, so I took it out to the garden to test it out. It ran good & smooth under load, and it certainly didn't sound or smell rich.

It seems like the main jet was machined too small originally. This is not the first time I had to do that to make the engine stop hunting and surging. Have you guys had the same experience with Tecumseh engines? Since I had to modify it contrary to OEM spec, I've got this nagging feeling that there's something else I overlooked. The valve lash was correctly adjusted. There was a manifold gasket that could be leaking, but that doesn't seem likely to me, since the screws were tight and no one had taken it off. What do you think?

[bgsengine]

Have had a couple or three relatively new (approx 100 hours, but 10 years old) Tecumseh OHV engines - essentially Honda Clones- with hunting and surging problems that even brand new OEM carburetor could not fix. All but one were actually resolved by replacing *gasp* the SPARK PLUG! ( with an NGK BPR6ES)


- Have had one other a V-Twin Vector that we did have to drill out the idle ports a little bigger to get a smooth running unloaded engine (ran fine under load, surged when not loaded) , and a little 5 HP vector engine that simply would not take any sort of fix until we replaced the complete air intake system including air cleaner box (it was plastic and warped) and updated the intake gasket/heat shield - then we threw the old carburetor back on it, and she ran fine with that too. - It isn't just the intake between throttle and engine that needs to be looked at - the vents and air passages in the front of the carburetor need to be considered too, as they are what meters air into the idle and main jet circuits for proper fuel mixing.

[bobodu]

You can always count on an Injun to hunt....I seen em hunt right out of the box.

[Mr Mower Man]

Have had a couple or three relatively new (approx 100 hours, but 10 years old) Tecumseh OHV engines - essentially Honda Clones- with hunting and surging problems that even brand new OEM carburetor could not fix. All but one were actually resolved by replacing *gasp* the SPARK PLUG! ( with an NGK BPR6ES)

Fascinating! How does changing the spark plug make such a difference?

[bgsengine]

As lean as they run, easy to mis-fire which can mimic the symptoms of surging. all the ones with the plug problem had either a non-resistor plug (N4C) or in one case, incorrect plug (Autolite equivalent of the RC12YC) - in short none of them had a RN4C or BPR6ES plug in them - we always use BPR6ES or BPR5ES in most Honda Clone type engines - in the case of the autolite plug, it was even brand new - it was installed by the customer, who watched me replace it (and argued that it was a brand new plug, the whole way) and should have seen his jaw drop when the surging problem stopped.