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Carb ma4spa

Christopher Murphy

Well Known Member
Frustrated!
I took my carb that, was running just fine, off to install the metal float kit. Put it back together using the 7/32 float dimension. Put it back on, it started and ran but was too rich. I took it off and lowered the float level using 9/32 dimension. Put it on and it leaked fuel from the vent on the bottom. Took it to the shop where a fuel tech reset the float to 7/32 tested the needle and seat( good) and tested it on the flow bench. All checks good. I put it back on the engine and it leaks even worse now. The float is not sinking.
Any ideas?
 
float kit

I installed the kit that the kelly aerospace rep at oshkosh told me was the correct one. He gave me the part number.

Ive had it open 3 times...condition and trash in the needle seat were checked by me and the fuel tech..as well as integrity of the float.

Its got me baffled?
 
IIRC, the metal floats are not the latest version. The newest ones are blue epoxy. I just installed a float kit in my MA4-SPA carb with no issues. Removed the older but functional metal (brass) floats.

YMMV
 
I am tempted to put the white float back in...
i hate fixing things that arent broken..

Definately DO NOT put the white plastic float back in, those are the ones that caused all the problems.
What is your fuel pressure running? (4-6 psi is normal)
 
metal float

The kelly aerospace guys said to go with the metal float. we had a long discussion about which float should be in the carb
we tested the needle and seat at 6 psi on a flow bench... it was fine.

put on the airplane and it pisses fuel out. 4psi max on the plane

it shouldnt be rocket science..lol

I will eventually figure it out but I was wondering if there was something else
that might cause that isse

merry christmas
cm
 
My carb shop would agree, the brass float is fine and they will re-use those but the white ones get replaced with the new ones because the brass is no longer available.

You may just take the carb off and hold it level to see if the same thing still happens, perhaps the steep angle is causing the issue somehow. I would also double check the FP with a seperate gauge just to be sure.
 
CM, it is kind of like the one piece/two piece Venturi swap from many years back, oh yes that really fixed everyone's problems. :D
 
The kelly aerospace guys said to go with the metal float. we had a long discussion about which float should be in the carb
we tested the needle and seat at 6 psi on a flow bench... it was fine.

put on the airplane and it pisses fuel out. 4psi max on the plane

it shouldnt be rocket science..lol

I will eventually figure it out but I was wondering if there was something else
that might cause that isse

merry christmas
cm
Hi Chris,
No real ideas right now as I'm not sure what they do with the venturi pressure on a bench flow test.
But FYI, just in case, I have a spare (new) O-320 carb in my hangar, in case of worst case,
GH
 
Maybe not an answer to your problem but...
I had flooding/leaking issues with 3 different carbs. on my 0320. 2 O.H. units were from Kelly Aero. The last one flooded badly right away, then poured fuel out after shutdown. Tried different settings for about an hour when all at once it just ran perfectly! Got out and discovered my fuel pump was leaking from the overflow vent. Tried this 3 more times, carb done fine but upon shutdown the pump leaked for 2-3 min.
Installed a new fuel pump and haven't looked back... Oh yea pressure on the old pump was 4-8 and the new pump runs 2-6 psi. ?????
 
thanks for the ideas

Ironic that i opted for the carb vs FI on the engine when i bought it new. Theory was the carb would be easier to work on...lol

Thanks for the offer Bill. I will get it sorted out eventually

The fuel system tech says they are finicky...


Cm
 
Solved maybe

I took my carb apart again today. It appears that the wire spring clip that holds the needle in place is contacting the, top or bottom, of the needle seat tube holding the needle from seating completely.

Im not sure how i can fix that issue but that appears to be the problem

Cm
 
wire clip

Bob,

Thanks for the reference. The clip that came with the float replacement kit is a wire clip and not the type in that SB.

I was out working on the carb today and for the first time took a look at the white floats I am replacing and I am glad I did. The pontoons are one piece and a second top piece is bonded to the top forming a sealed float. The top of one pontoon had started to deform and seperate from the pontoon.

I suspect the float valve seat in these carbs manufactured with the plastic float might be longer than older models. The plastic float used a small bracket to retain the needle.

As I mentioned earlier,,, I talked directly to the kelly aerospace rep about which float to use.. I would think they would know.. i hope.

CM
 
more help with carb need cf30-864 float

OK... Latest on this carb issue.

I can't make the metal float run right...too rich no matter what I do with it and it drips fuel.

Put the white plastic foat back in and it runs great but that float is unsealed.

Looked at the part number stamped on the new metal float and it is
cf30-766 and came in the kit part number for this carb.

The part number the kelly aerospace guys gave me was cf30-864
which appears to be the blue epoxy float...

I suspect this metal float is for a gravity fed carb only and the 4 psi from pump is keeping the needle open.

Does anyone have a good source for the cf30-864 float assy?

cm
 
You should be able to call Aircraft Spruce and they will get you a price quote. I've done that with magneto parts before.
 
OK... Latest on this carb issue.

I can't make the metal float run right...too rich no matter what I do with it and it drips fuel.

Put the white plastic foat back in and it runs great but that float is unsealed.

Looked at the part number stamped on the new metal float and it is
cf30-766 and came in the kit part number for this carb.

The part number the kelly aerospace guys gave me was cf30-864
which appears to be the blue epoxy float...

I suspect this metal float is for a gravity fed carb only and the 4 psi from pump is keeping the needle open.

Does anyone have a good source for the cf30-864 float assy?

cm



Aircraft spruce has what you need. Oops Bobby beat me to it. http://www.aircraftspruce.com/catalog/eppages/tempestvolareparts.php

Best regards
Bill
 
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no good

Aircraft Spruce
CARB FLOAT KIT # 666-915
AS p/n 07-00677 $109.00

This is the kit number and the float that have caused me so much trouble.

I should have looked at the float part number and not just the kit number.

Im done with the metal float!

cm
 
This is the kit number and the float that have caused me so much trouble.

I should have looked at the float part number and not just the kit number.

Im done with the metal float!

cm

Weird - that's what i bought from Spruce and it was a solid blue epoxy float.
 
Last edited:
finally flying again

The end of this story, I hope.

After getting a call from another local RV guy I just decided to call Marvel Schebler about my carb.... Thanks Bob E! Those guys were great. Gave me the 411 on Kelley aerospace, I ended up sending the carb to them so they could go through it. For the price of float and an hour of labor they completely went through it and test and checked everything. Came back looking like a new carb, installed and adjusted, runs great so far.

I always like to solve my own problems so I know in the future about these issues and how to fix them.

What I learned... I tried to make a metal float work because it was supposed to work in my carb.... it caused me much consternation and aggravation..... to top that off after I convinced ACS to take it back the kelley aeropace people wouldn't take it from spruce so I have a metal float I cant use.

second..... very happy with the people at Marvel Schebler.... highly recommend them..

Cm
 
Caarb

The end of this story, I hope.

After getting a call from another local RV guy I just decided to call Marvel Schebler about my carb.... Thanks Bob E! Those guys were great. Gave me the 411 on Kelley aerospace, I ended up sending the carb to them so they could go through it. For the price of float and an hour of labor they completely went through it and test and checked everything. Came back looking like a new carb, installed and adjusted, runs great so far.

I always like to solve my own problems so I know in the future about these issues and how to fix them.

What I learned... I tried to make a metal float work because it was supposed to work in my carb.... it caused me much consternation and aggravation..... to top that off after I convinced ACS to take it back the kelley aeropace people wouldn't take it from spruce so I have a metal float I cant use.

second..... very happy with the people at Marvel Schebler.... highly recommend them..

Cm

Marvel Schebler Carbs have been around a long time. The trail of owners is rather difficult to follow. Long before anyone heard of a plastic float, the Marvel carbs were successfully using metal floats.
Based on a rather long history of various problems with the "plastic" floats, I am going to do my best to make the Kelly metal float work. Kelly has been around a long time, although not nearly as long as the Marvel carbs. If there was some basic design flaw with the Kelly floats I think it would have put Kelly out of business some time ago.
There are a several things about the current Marvel Schebler that really annoy me. #1 is that they will not provide a parts list with part numbers. They consider this "proprietary information". #2 a bushing that would seem to be a very simple replacement is a "factory only" repair. They do not sell the bushing or provide any information on replacement. #3 While I do not have any first hand information on this it appears that MS bad mouths both Kelly and the metal float. This is contrary to various MS bulletins over a long period of time which make it clear that the Kelly metal float is acceptable and apparently always has been.
 
part numbers manuals IPBs

I felt the metal float would be fine. I listened to the kelley guys. I spent almost two months trying to figure out why it wouldnt work. I had the use of a flow bench, i had other A&Ps look at. It didnt have a bad float needle or seat. I started do reasearch on that metal float part number and found that many others had the same issue. Its got the blue epoxie float now. Ive worked on alot of carbs over the years including one of the most complicated (rochester 4bbl). I figure the metal float works on a gravity feed system but it couldnt handle over 2psi

If anyone wants a metal float they can have it for 10dollars

Cm
 
Carb

The metal floats worked for years in aircraft such as the Piper Apache with low pressure fuel pumps. This was long before anyone heard of a "plastic" float.
One issue that I have never seen mentioned is the need to insure side clearance between the float and the bowl regardless of float type. One of the MS "special tools" is a gauge to measure the installed float location to ensure side clearance. There are also potential interference issues with the needle valve clip and the float pin and cotter pin. These could affect any style float.
 
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