SD40 big window carb leaking. (1 Viewer)

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May 25, 2012
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Location
Heber City, UT
I hope there's a fix for this.

Last year, I bought the rebuild kit from SOR for my stock 1bbl carb and everything has seemed to work fairly well since then. Lately, I've noticed fuel leaking from it during and after operation. It seems that it is coming from around the window and there is a spot where the rubber gasket is deforming and getting sucked in behind the glass. I tried swapping back the old rubber that was in there and that lasted about a week and is also getting sucked/pushed in.

What am I doing wrong?

Am I tightening the metal bezel too tightly? Too loosely?

Should I use some sort of adhesive to keep it in place?

If this is letting air in, how much difference could that make in performance?

Please forgive my ignorance. I'm learning what I can as I go.

Thanks in advance.

Pics to follow.
 
Ethanol?

IMO if it were me I would take the old gasket and put a very light film of rtv blk on the gasket ... Make sure there is no gas wetness on any of the surfaces put it in when tacky secure and let cure for a day

I need to say that it is not recomended rtv in contact with gas... However I gave used ultra copper in the same manner with no issues ... But the copper would probably look bad on there even if its a light coat probably

Maybe others could chime in ... But... That's what I got :)
 
Here you can see where the rubber is out of its seat and not sealing near the top of the left side of the glass:
IMG_3540.JPG
My assumption is that this is the place the gasoline is leaking out.

I only use non-ethanol gas. I thought about using RTV but wondered if it would work exposed to gasoline all the time. I can't imagine if it were to dissolve that it would be an awesome "additive" for my fuel system. I guess letting it cure long enough would be alright.

I'll give it a try.
 
The RTV didn't work at holding the rubber in place but I don't think it was the RTVs fault.
Just to check, I pulled out my old, cracked gasket that was on there before and, lo and behold, the one from $OR isn't even close to a size that would make a good fit:
https://lh5.googleusercontent.com/-...OI/AAAAAAAAHzA/mzlqxonE0EQ/s800/IMG_3737.jpeg It's no wonder the old gasket was buckling and folding in on itself.

Does anyone out there know where I can buy a gasket that would actually fit?

Is there any kind of material that wouldn't dissolve in gasoline that I could use to repair the cracked old one?
 
did you get a keyster carb kit from SOR? last i remember 04211-60086 was still available from the dealer.
 
did you get a keyster carb kit from SOR? last i remember 04211-60086 was still available from the dealer.

Thanks, I'll give that a try. The dealership here in Boise has been hugely unhelpful but I realize 48 year old parts are pretty scarce. Are there any good dealers you'd recommend out here in the Western US?
 
I have been unable to find the OEM carb kit.

This time, I'm using the old, correctly sized rubber gasket and some permatex form-a-gasket #2. I'll post results after I let it cure for a while.
 
how warped is it?

The gasket?

It deforms pretty badly

In my first pic, the black spot in the upper left side of the glass is the rubber gasket pushed in probably 1/4-3/8"; enough for a lot of air to enter the carburetor in a place it shouldn't.

It's no surprise since this gasket that came in the $OR rebuild kit is obviously too big by about 1/4" in both dimensions.

So I pulled out the old one (right size) that I saved and seated it in there with form-a-gasket #2 hoping it will seal the cracks in the old rubber.
 
I have heard that Permatex can clog up the tiny passageways in carbs.

I had a similar problem on a d40 small window last week. In my case it was that one of the machine screws that fixes the outer plate to the carb body had stripped the thread out of the soft aluminum. I had to tap it to 4mm and put in a new screw. Yours looks like a gasket problem. A steady hand with an x-acto knife could make a new one. :meh: Worth a shot if you cannot find the right gasket.


65swb45 is the owner of Mark's Off Road and he might be able to help you out.

He doesn't respond to PMs too quickly but his phone number is on his website:

http://www.marksoffroad.net/
 
I have heard that Permatex can clog up the tiny passageways in carbs.

I had a similar problem on a d40 small window last week. In my case it was that one of the machine screws that fixes the outer plate to the carb body had stripped the thread out of the soft aluminum. I had to tap it to 4mm and put in a new screw. Yours looks like a gasket problem. A steady hand with an x-acto knife could make a new one. :meh: Worth a shot if you cannot find the right gasket.


65swb45 is the owner of Mark's Off Road and he might be able to help you out.

He doesn't respond to PMs too quickly but his phone number is on his website:

http://www.marksoffroad.net/

I had thought about calling Mark. I just haven't yet. That's my next move if this form-a-gasket doesn't work. I thought about cutting a gasket out of some thick rubber, too.

I still remember some of my scalpel skills from medical school so maybe I can hack a gasket out of rubber if necessary.
 
Soooooo

Jeremy’s carb wins the award for THE MOST WARPED fuel bowl on an SD40. He just sent me this link so I could post up some pics. I hadn’t seen this thread prior to now, and my initial pleasure at having a sight glass come out so easily soon turned to shock when I realized WHY it had come out so easily.
D9F73C1D-C021-43FF-9349-A69E6C07C4BE.jpeg
F8A32D56-332C-4F42-A77E-8CF1BDE0EA17.jpeg
0C29F794-FF75-42BF-AA01-7E89E51747E8.jpeg
 
Both the bottom of the air horn and the top of the fuel bowl were also pretty badly warped. That’s not great, but at least a little more routine.

I will post progress pics on the ‘repairs’ in a day or two.
 
On the bright side, the gas that has been leaking out helped to dilute the gear oil leaking out of the steering box so that it could flow down to keep the drag link lubed up.

That's some funny sheit there!
 

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