Stromberg Carb Questions

Hi,
Have been in the process of overhauling a C90-8 for my 46 J3 along with my A/I. The engine on the cub now is a 65 that along with the help of many here we overhauled the Stromberg carb and it runs great now. Made the float level adj. tool and setup bench to test it. Worked out great and was a good learning experience. I have just taken apart the C90 carb and found the needle was a neoprene type with very neatly inscribed numbers....not good as I understand it. I do have the new delrin needle on hand and will have to use it.

Two questions if I may. First ,the main appears to be a #49 and the air bleed I cannot see any markings. I have the overhaul manual manual and it seems to call for a #46/#60 combo. I am getting a set of numbered drills this afternoon and will confirm the sizes. Can one drill out the 49 to a 46 and have it function properly?

The second question concerns the installation of the delrin needle. The instructions call for a counterweight made form 3/32 brass stock. I have checked everywhere I can think of and have not come up with this size stock. Has anyone done this mod and where did you find the stock?

Thanks in advance for any help.......

I've found small brass stock at the local hobby shop.

Mark

Mark,

Thank you for the reply. I have checked all the hobby shops here and none have 3/32 stock. I really don't want to solder two pieces together on something as important as this.

make sure the brass weight weighs about 4 grams as per the instructions. You could use brass shim stock. I machined the weight out of a piece of solid brass, then weighed it.

john

I opted for the stainless needle and I know of a rubber tip needle that has worked flawlessly for over 10 years.

What Steve said - except I have 45 years of successful needling. Do you mean the entire needle is Delrin? If so, why not just get the stainless one or a neoprene tipped one? I have never heard of a needle/seat wearing out, but I have seen new needles that wouldn't work. That slot needs to be dead smooth.

Tom,

I have a t-craft with a c-85. I replaced my original derlin tipped needle with a steel needle. At the time I really didn't know the difference between the derlin and the neoprene. Of course it is all to do with the use of auto fuel. I think with the steel needle you don't have to use weights on the float. I had an issue of fuel leaking by the needle when the plane was parked with the fuel valve on. My IA didn't like this much, so I sent it off for an overhaul. I had Fish Creek Airmotive do it in Big Lake, Ak. Been flying it all winter and no dripping yet. John seems real knowledgeable on these carbs. Their number is 907-745-1631

Wade
Tok, Alaska

I, too, had a leakage issue when the plane was parked with the fuel on. I assumed, based on past experience, that it was fuel leaking past the needle--a fairly common occurrence on a stromberg.

Last weekend I discovered an alternate explanation. More fuel was leaking and the engine was running richer than normal.

I pulled the carb and we quickly discovered the culprit. The float had a very small hole in it and was filling with fuel. Hence the richness and the leaking. It can get rich enough to stop the engine.

So, if you notice your leaky stromberg is leaking a bit more I highly recommend pulling it.

jrussell wrote

I pulled the carb and we quickly discovered the culprit. The float had a very small hole in it and was filling with fuel

Click to expand...

I know you're not running any ethanol so am wondering what may have caused the hole. Any ideas?
Thanks Marty

180Marty said:

jrussell wrote

I pulled the carb and we quickly discovered the culprit. The float had a very small hole in it and was filling with fuel

Click to expand...

I know you're not running any ethanol so am wondering what may have caused the hole. Any ideas?
Thanks Marty

Click to expand...

The leak was on the solder seam, so we suspect age and perhaps an initially weak solder joint on a portion of the seam.

We took the float apart, cleaned it up and resoldered the two halves. Right now it is in the bottom of a tank of water for a couple of days to see if it leaks.

Otherwise, the carb is in superb shape. There is a lot to be said for the simplicity and robustness (my float aside, of course) of the mighty Stromberg.