Carb rubber gaskets - what the heck??

C

cfh

Well-Known Member
#1
#1
Admittedly, i'm using $10 carbs. But i've noticed the rubber float bowl gaskets on both Tecumseh and Predator carbs, after being used, are like hugely oversized. To the point where i can't use them again.

If i remove a float bowl, the rubber bowl gaskets are just too large to get back into place. It's like they stretched!

what is causing this? Yes i am running standard pump gas which is 10% alcohol.

i mean it's not a huge deal. A new carb in either case is like $10 (including shipping!) but i can never remove a float bowl for fear that the rubber gasket will no longer fit.
 
Last edited:
H

Havasu Dave

Moderator
#2
#2
I had to resort to ethanol-free gasoline to avoid replacing ten dollar carburetors every few months, and rubber swelling was half of the reason.

Some of my problems with the cheap carbs were caused by the float needle seat swelling. This caused overfill of the bowl, as the needle no longer penetrated deep enough to shut off the fuel. And yes, like you, when I pulled the bowl to investigate, the rubber no longer fit.

I do not see this swelling as often with the Tecumseh and Tillotson carburetors, nor in my Carter AVS on my Dodge. Might be a slight difference in what the rubber compounds used in Chinese based rubber is, might be a fluke, but I think it's a combination of ethanol and cheap rubber.

Ethanol eats everything. Even fiberglass and epoxy.
 
C

cfh

Well-Known Member
#3
#3
is there really a good answer here? I mean even the predator carburetors have this problem. It’s not just tecunseh china carbs, it’s pretty much everything. Using ethanol free gas is an idea, but it’s not available everywhere.
 
S

SAT

#4
#4
IDK on the gasket stretching. We are running Rec 90 with sea foam and have had zero bowl gasket issues. Stens, Oregon, Tecumseh, Briggs all with no gasket problems. Admittedly none of our carbs have been fed any other fuel, so no chance for the pump gas exposure. Even if that’s it. Internal casting problems are the biggest pain found in the amazon aftermarket carbs. Oftentimes it’s a crap shoot.
Change fuel to Rec 90 for a year and have a look-see.
Hope this helps,
Steve
 
Davis

Davis

Well-Known Member
#5
#5
cfh said:
is there really a good answer here? I mean even the predator carburetors have this problem. It’s not just tecunseh china carbs, it’s pretty much everything. Using ethanol free gas is an idea, but it’s not available everywhere.
Click to expand...
You actually got a great answer don’t use shit fuel and your good.
 
H

Havasu Dave

Moderator
#6
#6
cfh said:
is there really a good answer here? I mean even the predator carburetors have this problem. It’s not just tecunseh china carbs, it’s pretty much everything. Using ethanol free gas is an idea, but it’s not available everywhere.
Click to expand...
No, there are no good answers. Use ethanol free fuel on your carbureted engines. We went to ethanol, and we went to fuel injection, and those of us left behind are out of luck, unless you have a source of ethanol-free gasoline.

Predator carbs are made from the same junk the ten dollar Tec carbs are made from. (and probably the Tillotson rebuild kits as well)

Another solution is to source BUNA-N O-rings that fit the bowl and float seat, and replace the Chinese rubber. I've had good luck with the BUNA O rings in fuel injection systems, but never attempted to source them for the bowl.

We will see this failure more often in systems that are adjusted or worked on more often. Common sense, right? But when you also have a needle seat rubber failing, you're going to be pulling that bowl. And for those of you who live in colder or more humid climes, you are also dealing with the corrosion caused by quick evaporation of ethanol creating H20 in your gas, which makes quick work of brass and aluminum components- which is also going to have you pulling your float bowls. Ethanol sucks.

I've stated several times how much better all of my air cooled engines ran with ethanol-free gasoline. It's unrelated, but it is a bonus.
 
C

cfh

Well-Known Member
#7
#7
I've noticed if you let the rubber gasket dry, it seems to shrink back to it's original size (or pretty close.) which is totally weird.
 
Skipp

Skipp

#8
#8
When rebuilding linkerts I try to find gaskets made of viton....seems to resist fuel and other impurities...I use 90 octane strictly which here is non ethanol...I personally haven’t had an issue but I replace a gasket every time I take torque off of it.....
 
You must log in or register to reply here.
Top