• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Leaking Carburetor Cause Discovered.

Alex Clark

Alex Clark

Registered User
Life Long Alaskan
As a follow up to my previous, and poorly explained, post about my leaking carb on the 12.
It turned out the float decided to be a submarine. See attached photo. So it filled full of fuel and sank.
Thus it was flooding like crazy. So a new float is on order.
I have never seen a semi-clear white float before. It has a Eagle or Hawk face logo.

As I am sure you know. there was a 2009 service bulletin regarding improper floats in Marvel Carbs.
https://msacarbs.com/pdf/SB-2_B_RPLmnt_of_Foam_and_Hollow_Floats_062209.pdf

We also discovered that the primer lines were spraying fuel into the engine compartment every time the primer plunger was pushed. This was adding to the fuel dripping all over the place. So that is the next thing on the list.

NOTE: The IA who installed my new aluminum tanks was not the IA who last tinkered with the carburetor.
 

Attachments

  • Carb float flooded 2.jpg
    Carb float flooded 2.jpg
    373.8 KB · Views: 54
Last edited:
Preflight when cowling open I give a tug on each primer line..........they have a tendency to break off in the fitting that's not visible.
 
Cubdrver
The fitting going into the cylinders were just fine. The major spraying leak was up above the carb behind the engine. Somewhat concealed.
The is a splitter fitting that sends gas from the one line off into port and starboard directions. When I pumped the primer it was spraying 5 inches out of the fitting.
You had to have somebody pump while you look. It was a nice mist. Perfect to start a friggen fire.
 
Hope you got an Avstar brass float. The blue Marvel ones aren’t super consistent, apparently. Had a weird lean range on a fresh c-90 carb from Marvel, sent it back to them, came back the same. Talked to a highly experienced carb repair station up here, and was told to throw the Marvel float in the trash- apparently he sees this commonly. I didn’t listen the first time, gave Marvel a chance to warranty it, but after the second go-around, I put the Avstar brass float in, and totally cured. Anyone else heard of issues with these? And no, it wasn’t cracked or sunk…
 
If it wasn't cracked or sunk, it might be like my old plow truck, where a composite float distorted and rubbed the inside of the chamber. What does Marvel say about mogas?
 
ak49flyer said:
Hope you got an Avstar brass float. The blue Marvel ones aren’t super consistent, apparently. Had a weird lean range on a fresh c-90 carb from Marvel, sent it back to them, came back the same. Talked to a highly experienced carb repair station up here, and was told to throw the Marvel float in the trash- apparently he sees this commonly. I didn’t listen the first time, gave Marvel a chance to warranty it, but after the second go-around, I put the Avstar brass float in, and totally cured. Anyone else heard of issues with these? And no, it wasn’t cracked or sunk…
Click to expand...

What was the “weird lean range” you noted?

MTV
 
Missing at mid-range, particularly while running on only one mag or the other during a check. Carb heat would almost cure it completely, but the float did away with it entirely. Spent days troubleshooting, finally swapped carbs with another to conclusively rule out anything else, and it was indeed the new carb from Marvel.
 
Thanks for the follow up Alex.

I have seen floats do that a number of times in the automotive side of things. Its always been with the newer plastic floats never the old brass ones. Seems like the plastic ones develop leaks along the seam usually or the composite material breaks down prematurely.
 
Now the fuel inside the float will not come out. It has been hanging for a over a week now and the fuel level inside has stayed the same.
Pure Friggen Magic....
 
It may take a major change in temperature to get the float to take in or release fuel. Put some ice or hot air on it and see what happens?

Gary
 
ak49flyer said:
Hope you got an Avstar brass float. The blue Marvel ones aren’t super consistent, apparently. Had a weird lean range on a fresh c-90 carb from Marvel, sent it back to them, came back the same. Talked to a highly experienced carb repair station up here, and was told to throw the Marvel float in the trash- apparently he sees this commonly. I didn’t listen the first time, gave Marvel a chance to warranty it, but after the second go-around, I put the Avstar brass float in, and totally cured. Anyone else heard of issues with these? And no, it wasn’t cracked or sunk…
Click to expand...

The blue floats you're talking about...are they the foam floats?
I thought those were supposed to be the ticket,
solid foam so impossible for them to fill with fuel.
 
Interesting thread... I have a suspected tiny leak in my carb as well, nothing like yours where its was draining fuel. I s a carb rebuild something that can be done at annual or is it best to send it out? If you send it our who do you all recommend?
 
Simple float level check, gasket change, float swap, etc can be done at annual, but a real checkout/overhaul involves a flow bench, which involves sending it to someone. After having poor experiences other places, I’ve taken to sending/exchanging with Avstar. They will overhaul/exchange MS carbs as well as their own, but the put their brass floats in, so that kills that issue. So far I’ve been happy- they’re a relatively small company with great support…
 
FIXED Carb has been re-installed.
New Primer Lines fabricated.
Primer nozzles cleaned out.
Now Starts immediately.
Runs great.
No Leaking fuel.
Potential buyers have so far just been tire kickers
 
You must log in or register to reply here.

Similar threads

WindOnHisNose
Dead Stick Landing...An Auspicious Start on the Journey to Johnson Creek
2 3
Replies
63
Views
32K
coxcub
coxcub
S
Barnstorm 2021: A Supercub Flying Adventure Across America
Replies
1
Views
1K
mam90
M
D
Barnstorming 2021
Replies
1
Views
2K
JP
JP
I
AK Troopers cubs
2
Replies
34
Views
8K
wirsig
wirsig
Back
Top