Will Methonal ruin rubber tip's on Float Needle Valve?

Anyone else had this problem? I installed them new 4 month's ago! Seat's and Valves.

Went out to start the bike turned on the fuel started it and Number 3 wasn't firing. put hand over said carb and No fuel was getting to it so I choked it by hand till fuel started flowing and cylinder started firing then I noticed fuel dumping out number 2 carb. So I took the Rack off pulled the Bowl's and Low and behold 1 of the 4 valves had the rubber tip's pulled out of the lower part of the valve and was stuck in the seat! #3 carb of course and 1 of the 4 was broken at the bottom of the rubber tip sitting sideway's #2 on closer inspection the #1 and #4 was loose in the valve and just resting there.

Before the questions. No, I do not let bikes sit around with fuel in the bowl's for extended periods of time. I learned that lesson along time ago. I don't use any additives. Yes, these carb's have been torn down to the bodies. Boiled, scraped, rubbed, scrubbed, polished, cursed, cussed, and bled on ( little butter fly screws and slipping tiny screw driver). all of the throttle shafts seals were replaced, fuel line o-rings, idle screw o-rings, new jets anything that could be that was rubber was replaced.

The part's came from a reputable source.

Inferior part's? or is today's fuel just not working with all the rubber part's in these older carb's?

Ok here's a pic
You can see the 2 that are broken and other 2 fell out.

 

I have had the same problem with aftermarket needles. I would say its the manufacturing and not the fuel. The tips should be made from viton, its resistant to most any fuel. I have not had that problem with OEM parts. A small dab of CA glue held them together for a few weeks until I got new ones.

 

Ethanol will not ruin rubber, but methanol will, if I am not mistaken. Why did you have these parts exposed to methanol?

 

Well to tell you the truth Not sure how.

The fuel in question came from a local Station that has long been known as unreliable for fuel quality and shady practices.


I usually get my fuel from this place.
Ethanol Free

 

It likely a combo effect, inferior AM parts and the crappy fuel.

The gas-ethanol or methanol mixture IS a problem, but it isn't as simple as the language suggests. Ethanol or methanol by itself in a short time (less than 45 days) won't significantly damage synthetic or natural rubber, Isopropyl is much faster. Although ethanol does have an affinity for 'carbon black', it's in rubber, and will attract it into solution given enough time.

The real problem comes when you mix the alcohols into the gasoline at the levels they are using. Gas is a chemical soup, with stuff like MTBE and other complex compounds, when these all get together and SIT ethanol becomes much more problematic. Small amounts of ethanol derivatives are created; acetals, ketones, and aldehydes and they are very reactive with the rubber, this only happens in tiny amounts but it's enough. Combine that with the solvency of 'carbon black' and the varnish that develops from MTBE+E10 and other chemicals in gas and your rubber will suffer. If water is present (marine or boating) or it's a two-stroke these problems are greatly enhanced. If you ride your bike on a humid day then park it for three weeks you almost certainly are conducting a organic experiment in your carbs.

Just running the motor long enough to fully evaporate the moisture and not letting the gas sit unmixed for more than 10 days or so should prevent any problems, but using E free gas or a stabilizer is a better bet.

Viton is highly resistant to almost all solvents-GOOD STUFF. Thanks Dupont.

No more science %$#@