marking thread for later.

 

I use Teflon tape myself and have been for years.

 

You are on the right track here, but...the main reason you should use viton is that nitrile (Buna N is a brand name of material) is only good for running at around 80 degrees C or else it starts to harden and deteriorate, especially in an environment which shows a lot of temp fluctuation - i.e. on a bike.

If you have bought a whole box (lifetime supply) you should store them in a dark environment away from UV light - but actually I wouldn't store them for more than about 5 years anyway and as they are so cheap it is not worth taking the risk.

It is important to use viton and also pay attention to the shore hardness (70 shore is the number in the opening post). 70 shore is a "standard" and will generally be assumed by any trade counter sales person, but that may not be the right answer. Use nitrile and you will be changing out very soon and murphy's law states it will be the one which is the biggest PIA to get at! Also, if you have both types then bin the Nitrile, you need an experienced person to tell the difference.

Viton is good for 120 degrees C

The industry standard code for the O'Ring is BS013 (this is a British Standard but recognised by anyone reputable seals person).

 

I have such a diifficult time allowing inaccurate info to pass for facts on this forum. I'll apologize in advance for boring everyone with the facts:

"the main reason you should use viton is that nitrile (Buna N is a brand name of material) is only good for running at around 80 degrees C or else it starts to harden and deteriorate, especially in an environment which shows a lot of temp fluctuation - i.e. on a bike."

Not really close.

-You don't need to use Viton. Any fluoroelastomer oring will do.

-Buna N is not a brand name. The "Bu" comes from butadiene, the "na" comes from sodium and the N is from Nitrile. CHEMIGUM ® , HYCAR ® , PARACRIL ® , PERBUNAN ® are Buna N brand names. Viton is a Dupont brand name. Fluoroelastomer/fluorocarbons/FKM are generic names for the same elastomer. Buna N orings are good from -34C to 125C (-30F to 257F). Fluroealstomer orings are good -25C to 250C (-13F to 482F). Fluoroelastomer orings are used for their higher temp capabilities and broader chemical resistance to accomodate a wider range of tranny/motor lubrication additives.

-"Viton is good for 120 degrees C": Viton (Dupont) orings or any fluoroelastomer oring is good to 250C.

-The o-ring sizing standard in the US is AS568A. It's mentioned in the McMaster Carr catalog. The correct AS568A "dash" sizes for tranny plug and engine plug are mentioned earlier in this thread.

That's probably way more detail than anyone needs to know about orings but they are the facts.

 

Glad that's worked for you!

But Teflon tape is really just for pipe threads. And should not be used in hydraulic or natural gas systems because of the danger of small pieces coming off and clogging something up.

 

With the exception of 1 O-ring that was mangled on a new bike at the 1st service I've never had to replace one of these. I look 'em over real good each time a plug comes out, they're always fine. I've never replaced a derby cover gasket or inspection cover gasket either, just clean 'em, inspect 'em and reuse 'em for years and years. No drips, no weeping... just lucky I guess. Still a good idea to have spares laying around, that way you probably won't need 'em.

YMMV.... TL

 

I agree regarding hydraulic systems and engine/tranny plugs. Ptfe tape works great in stationary applications but can't provide the same sealing ability that an oring brings.

Regarding natural gas systems. There is a special high density yellow ptfe tape that is designed for natural gas systems. See below.

Yellow Gas Line PTFE Thread Seal Tape is an extra heavy, full density PTFE tape especially for gas lines. Recommended leakproof sealant for lines carrying natural gas, propane, butane; and water, oil and chemical installations. Use on pipe, conduit, valves, bolts, anything with a thread. Permits easy disassembly. Use on plastic, stainless steel, aluminum and all metals, ceramic, synthetic rubber, monel and carbon pipe. Pressure rating 10,000 PSI; .0035 mil thick, tolerates -450°F. to +500°F. Meets Federal Specification T-27730A. UL listed.

 

I agree that you will find all the documentation you want verifying the temperatures you have stated so I would not argue that with you, but from personal experience and accepted best practice in the fluid power industry one does not run up to temperatures anywhere near what you have quoted. I understand that the temperature limits I have quoted are not down to seal consideration only, but I am saying that the temperature limits I have quoted are when considering seal material limits.

I have personally experienced repairing machines that have been subjected to overheating (90 to 100 degrees in hydraulic systems) and the seals HAVE deteriorated, hardened and leaked. This deterioration can also be quite rapid and the sight is not pretty. This experience is not once or twice, but a number of occasions.

Cost difference between the 2 is pennies, so I struggle to see the point in even considering not using Viton, but that is everyones choice.

 

peddler is correct on all counts
A standard Buna o-ring is all that is necessary for the drain plugs. If one gets torn or hard replace it - they're cheap and easy. Thread tape or dope is for pipe fittings only and should never be used on your drain plug although I have cleaned that stuff off (and replaced their torn o-rings) after every HD dealer service I ever had. Those clowns never do my fluid changes, only (and reluctantly) warranty repairs.
Been doing hydraulics and mechanics for over 30 years and the quickest way to an oil leak or plugged orifice is with thread tape or dope. Particularly if the oil is under pressure. That stuff just wasn't designed for petroleum products.

 

I do agree with that statement and accept the error made