Stromberg carb problem

[a3holerman]

Hi,

I had posted a while ago about overhauling a stromberg on my C-65 46 J3. We did overhaul it and wound putting on new Slick mags and that made a world of difference. I had a situation yesterday that to say the least gave me some concern and was wondering if anyone might have some thoughts.
I haven't flown it much this winter but yesterday was a nice calm 40deg f ish day. A couple shots of prime and started right up. Flew for a solid hour and on wheel landing at our grass strip a gust caught me and send me for the pucked brush full rudder wasn't helping so a I gave it some throttle.........eased it up to 1/4 to 1/3...Nothing....kinda didn't do anything....back to idle as a easy advance and it finally caught shooting me away from the pucker brush. All was OK but I was very upset at the lack of power when needed. I am thinking the idle screw may be helpful. What is the ballpark setting? Under the described situation does it seem it may need to be richened or leaned?

Any thoughts you might have will be greatly appreciated...

 

[d.grimm]

Was carb heat on?

 

[a3holerman]

Yes the heat was still on.

 

[fireball111]

carb

Is your throttle cable casing properly tied at both ends ,i herd they can slip out.

 

[a3holerman]

Actually the cable was not tied at the throttle end when I got the plane last year but during the carb overhaul it was corrected. No, this was a didn't take the gas problem ,although I did advance it somewhat slowly it still did not want to accelerate.

 

[behindpropellers]

Whenever I fly the cub with the c90 and stromberg I never just pull the engine totally back to idle. I sorta goose it the whole way in because it just does not like to rev up quick from an idle on final.

Tim

 

[bob turner]

Mine does fine at idle on the descent, but if I move the throttle rapidly to wide open it will quit. That's because the air flow at idle is not enough to suck fuel out of the main metering jet. Once you get it off idle a bit, it will take hold. Try for a smooth push on the throttle - say, a minimum "three potato" push.

 

[PA11 Pilot]

I have a Stromberg on a C90-8 . The idle screw is 1and1/2turns out.I don't know if its the same on another horsepower engine but I have no lag. I had a very savy carb guy tell me that the idle screw adjustment on a Stromberg should be 1 1/2 turns out. It works great for me.

 

[bob turner]

OK - the instant you open the throttle, the idle jets are simply non functional. The one above the butterfly gets sucked on because the butterfly is closed; the one just below it functions with the butterfly barely open, due to venturi effect. The main jet uses a venturi that is bolted in above the idle area, and requires more air flow. That's why the darn thing won't start if the idle circuit is dirty. So I don't believe the idle adjustment has anything to do with operation at normal throttle settings, let alone full throttle.

 

[Ron Babos]

hesitation

a3holerman: There is no accelerator pump in the Stromberg so this is somewhat normal. A slightly richer mixture on the idle screw will help somewhat as there is more excess available in the system for the transition to midrange. I vary mine from a half turn between summer and colder weather. Richer for cold weather. As mentioned, don't use full idle unless you're done and get in the habit of smoother throttle movements. Never had a problem with my Champ, but the throttle ratios may be different than a Cub.
Ron

 

[fireball111]

idle

I had similar problem ,raise up rpm to 600 rpm witch also helped between
idle jets and main jets.

 

[Greg Smith]

There is no accelerator pump, but there is an accelerator well... A little annular ring at the base of the main discharge. It fills with fuel, and when the throttle plate opens and mass airflow goes up, it gets discharged in addition to the rest of the fuel from the main metering circuit. It, like an accelerator pump, keeps the engine from faltering due to short term leaning.

Did the engine stumble, or just not accelerate?

The idle circuit doesn't operate above idle. Actually at high power settings is can augment the main air bleed by pulling air in.

Don't listen to me as if I know what I'm doing. I've (usually) been wrong before... I just finished Fuel Metering, my last A&P class. I start taking my FAA written exams next week.