The Cessna 120-140 Association Forum

I'm looking for some input on my Stromberg (C-85). I've been flying this carb for a few years, since I bought the 120, and got used to the way it worked. Never owned a Stromberg prior. I removed it a few weeks ago to look it over, it was all crusted up bad and really needed a total clean up. I disassembled the carb, soaked it, cleaned it all up nice. I'm an A&P. I installed it back on the plane and now it responds very different then before. I'm at a 5000' airport. The carb used to stumble from idle to WOT, as expected, but ran just fine. The mixture was very sensitive and would nearly choke out the engine at about 1800 + RPM. I only needed about an inch on the mixture pull to lean at cruise (6500'). Not owning a Stromberg before this was my standard.
Now with the nice cleaned up Stromberg it no longer stumbles from idle to WOT, runs fine but the mixture responds much different then before. Now the mixture in not so sensitive, I can pull it full lean (it does work) but won't choke out the engine. Now the mixture can be pulled 3+ inches to start leaning at cruise (6500"). EGT is much lower on take off and cruise until I start leaning (1200). Normal cruise lean about 1350.
Anyway..... I'm looking to find out how a normal Stromberg acts to see which direction I'm going. Seems to be all around richer than before.
Note: The mixture arm has the extension added.

I've only flown behind a Stromberg with our 140 for 36 years, now, so still trying to figure it out . It sounds to me like yours was functioning "pretty well" and similar to most before the clean-up and you've improved its operation even more with a bit of work. Congrats! RE the mixture, I've joked that I don't normally use my mix control until near 30,000' as it just isn't "needed" but, real world, it is useful at/above 5,000'. Many are just wired full rich, of course, and just not utilized, but I do think it's good to have it operational as designed(?). It does sound like you have yours set up perfectly and functioning very well, especially for your field/area altitude. Yep, congrats and thanks for sharing! Mac

I use the mixture on my Stomberg to lean at any altitude in hot weather. One finger width. I’m pretty sure it is doing something because if I get a fouled plug, typically from extended ground operations, and evidenced by slight shaking in the control yoke, it will clear it.

I had my carb serviced twice since I bought the plane over ten years ago. It works well (though it will stumble when applying takeoff power in cold weather), no leaks, and seems to do the job well enough.

Mike