Tecumseh H35 runs good, except just one little thing.

[creia]

Tecumseh H35 - 45592R ser 7120B
This is a 3.5HP horizontal shaft engine with the diaphram carb that is on a Sears edger. We purchased it real cheap as it was non-running. My son and I went through it and (ultimately) were able to get it running pretty good.Here is the odd part, however and the reason for my post...
These carbs come with both an idle and high speed mixture adjustment screws. The Tecumseh default setting for these is one turn out, then adjust as/if needed from there for best performance. After cleaning (ultrasonic) and rebuilding the carb, it would just barely run- chugging and spewing black smoke and would quit if we opened the throttle at all. I can get it to run pretty good and take throttle ONLY if the high speed screw is only opened no more than 1/8- 1/4 turn (The idle speed at 1 turn out is OK). My guess is that the hole in the carb body that the high speed screw goes in to has been damaged (enlarged) by someone tightening it down too much or using the wrong screw. What do you all think?
Michael

[KE4AVB]

Double check your gasket diaphragm order. Normally it is the gasket and then the diaphragm except on the "F" carburetor. Other than it could be someone has damage the main needle or seat or even both; never know when someone has worked on these.

[creia]

Thank you for the reply KE4AVB! We were aware of the diaphragm and gasket order being critical (and this is a carb with the "F" stamped on the carb body)
Update: My son found a couple of old used Tec diaphragm (parts) carbs we had stored away. I pulled the high speed/main needles out of both of them and compared the shape and taper of their tips with the one in this H35 - significant difference! So I tried swapping one of them out with the one in this H35, and set the Tec default/starting setting at one turn out and the engine ran! We let the engine warm up good and dialed the high speed screw in to 1/2 to 3/4 turns out- A big improvement (and much more normal) than the 1/8 to 1/4 turns out we had previously. It appears that someone put the wrong needle in or the needle was excessively worn, or both. I am just glad that the seat was not damaged.
Michael