National Aeronca Association Bulletin Board

ff,

I had the same experience with a '56 JD tractor as you did with the motorcycle.

It started so suddenly that I almost fell off the seat in surprise. I, too, used StaBil.

I finally decided that I used too much SB which is easy to do. At least it kept the carb from getting gummed up.

Well, after many months I'm VERY happy to say that I'm back in action !!!

After all that... It turned out to be something jammed in the main-jet. We don't know what, because as the mechanics were handing the jet back and forth trying to peer through the hole, whatever was in there fell out on the floor, and they couldn't find it.

Other than that, they patched my lower cowling that had some pretty serious cracks, and a few other odds and ends.

Anyhow, I couldn't be happier. Back in the skies !

Thanks again to everyone for all your help and suggestions !!!

Bob K.
Anchorage, AK

BobK wrote:Well, after many months I'm VERY happy to say that I'm back in action !!!

After all that... It turned out to be something jammed in the main-jet. We don't know what, because as the mechanics were handing the jet back and forth trying to peer through the hole, whatever was in there fell out on the floor, and they couldn't find it.
Thanks again to everyone for all your help and suggestions !!!

Bob K.
Anchorage, AK

Congratulations. Problems like that drive me crazy. Some years ago my dad had purchased a new Suzuki LS650 motorcycle. It just didn't run good. He was a great mechanic and decided to take a peak inside the carb. In one of the jets was a very dead Japanese ant.

Glad to hear it and bet that it feels good to get back up in the air!

Joe

This goes to show that just because something is fresh from the repair shop doesn't mean it is good.

I had the same thing happen with a prop governor. The Repair Station had put it together wrong and I wasted hours trying to make it work!!

Does anyone know if there are any carb cleaner additives that would be safe to try when facing such an issue.

Tim

Marvel

nkh

Tim Juhl wrote:Does anyone know if there are any carb cleaner additives that would be safe to try when facing such an issue.

Tim

Sure! The carb additive called a screwdriver! Take it apart and inspect and repair as necessary!

Joe A

Tim,

I've had good luck with spray can carb cleaner run through the carb fuel intake then flushed with fresh gasoline, avgas if available.

The fuel bowl needs to be drained or empty first, otherwise the needle valve won't let the carb cleaner in.

If any jets or ports are gummed up this may or may not help but it sure won't hurt.

The saga continues.....

It ran just great for about a week, then all of a sudden, started doing the same thing again. I took it back to the shop, they pulled the carb and found a few chunks in the float bowl, and cleaned them out. (Nothing in the jet this time) Put it back on, flew it around the pattern twice, and all was well. Landed, said thanks, and then headed out to play on some gravel bars with a buddy. 20 mins into the flight, I pull the throttle to descend, and it acts up again. (Son of a.....)

This time I spent about an hour trying to diagnose/cure the problem while flying. Carb heat, mixture, throttle changes, etc... I even tried some abrupt maneuvers, thinking that maybe I could dislodge a blockage, if there was one! I isolated the RPM range where its acting up. 1800-2250rpm is the spot where it just coughs and sputters, acting like it wants to die. Above or below that range it runs absolutely great. Pulling carb heat while in that range makes the problem disappear immediately and completely.

Dropped it back off at the shop... They pulled the carb again, and didn't really find anything this time. They went further back up into the fuel system, and found a couple things, but nothing that would make it past the gascolator screen. Gascolator looks good. They upped the main-jet one size, but I dont know why that would fix the problem, as it already ran fine at full-throttle. I mentioned the transfer ports possibly being blocked, and they said they had cleaned them out more than once.

Its all put back together now, and Im supposed to go pick it up this afternoon. Im doubtfully hopeful that the problem will be solved...

I'm sure it would've been easier to buy a new carb, but when I called Kelly Aerospace a few weeks ago, they said they don't have any new carbs to sell, and that Id have to send mine in for them to rebuild if I wanted one.

I'm almost positive that my problem is carb related. I cant imagine that a hung valve would *instantly* go away with the application of carb heat. If the problem returns, I think my first step will be to try the MMO routine, and hope for the miracle in a bottle cure... After that, I'm thinking a new gascolator and a complete tear-down/rebuild of the carb may be in order. (Performed by me, and checked out by an A&P)

Thanks once again for listening, and providing many years worth of wisdom!!!

Bob K.
Anchorage, AK

Bob,

Sure that you do not have a hose assy or fuel tank liner coming apart and putting crap in the system?

Joe A

It still sounds like carb. My guess is it is running too lean at full throttle which is the reason they increased the jet size, larger hole = more fuel.

There is always the outside chance of an ignition problem. I once had the spark plugs on my Stinson gapped too wide and it did the same thing - everything fine except at full or near full throttle.

Valve Springs.

http://www.supercub.org/phpbb2/viewtopi ... lve+spring

nkh

It lives!!! (So far, at least...)

Picked it up last night, and flew it around the patch for about 30 mins to make sure it ran ok before I headed home. All was well, so I headed home.

They pulled the carb apart, and cleaned the heck out of it. Drilled out the main jet a tiny bit also. They also went back up through the fuel system and found just a few flecks of junk, but nothing that would've made it past the gascolator screen.

The fuel line coming apart makes sense to me, so if the problem returns, I'll be sure to replace the hose from the gascolator to the carb. Its the only rubber line in the system that I can see.

The valve springs have been checked (at least while still installed), but that was one of the things we checked before we yanked the carb for the second or third time.

We'll see how things shake out over the next several days, and hopefully my woes are behind me. I cant say enough good things about my mechanics Mitch & Scott from Precision Plus in Birchwood. They have been extremely helpful, as have all of you!

Thanks again!!!

Bob K.
Anchorage, AK

Maybe you should consider to just plan to replace the fuel line between the gascolator and carb at your next annual.

I may do this as well. I keep finding small flecks of stuff in my gascolator. But in my case, I believe I found the source to be my aux fuel tank. I stopped using it. But still find a few flecks of debris in the gascolator. Maybe it is he rubber hose deteriorating. Seems like a pretty benign and low cost preventative maintenance item.