Oil seals: Define "good."

How many ways can you tell if your oil seals are "good"? I am confused. Just with leaks? Can you merely "look" at them and determine their quality? I have had one old auto mechanic advise me that you should run your bike regularly so that the seals don't dry up and become brittle.

But you guys in cold climates store bikes for weeks-months during winter. The forum is full of stories of bikes long (years!) unused that start up with some cleaning and new gas and plug. So, what determines a bad oil seal? How "brittle" is "brittle"? Do you just change them if you open the engine because you're already there? Guidance, please. (The cost of a seal for an E50 engine is $6.25. That's one of the reasons I ask.)

Re: Oil seals: Define "good."

If the bike was setting for a long time then replace them. Its just one of them things.. you do. Yea sometimes you get lucky.

Re: Oil seals: Define "good."

The tools and experience required to accurately test for seal leaks outweighs the cost and effort of simply replacing them with new ones and being confident that they are good.

If you regularly trouble shoot old engines, you might want to look into leak down testing procedures, but in the meantime, just replace them.

Re: Oil seals: Define "good."

You could make a leak down tester, shouldn't cost too much. Take one of those blood pressure cuffs, a few aluminum block off plates, some barbed fittings and a pressure guage that goes up to a few psi.

Grey

Re: Oil seals: Define "good."

be aware that the crankcase pumps up to only about 6 psi or so .. when testing seals use a hand pump and keep the pressure low or you'll blow a seal that may have been good.

i deal with pneumatic and hydraulic cylinders.. the seals may get "brittle" and not seal, but the seal still feels flexible. Sometimes they are so brittle they crack when bent.. Sometimes an aparently brittle seal seals just fine. I think it's a matter of the neoprene losing some of it's chemistry over a period of a year or years of non-use.

the only worthwhile observation is whether there's a leak or no leak.

Re: Oil seals: Define "good."

I've seen seals that cost $20 or more, less then $7 seems like a good deal, also it should have a part number on it, alot of auto part stores can order based off that part number, on one of my motorcycles I think it was $1.30 for a new shaft seal, when the dealer wanted over $25... it had the same size number on it.

Re: Oil seals: Define "good."

A. J. Souza /

Thanks to joew; always there with a reasonable reply.

Ryland: Yeah, I have tried the auto parts stores, to no avail. They never even got back to me with responses. The problem we have here is that there is only one place to buy bearings and seals on the island and they consistently have prices that are higher than I see you guys referring to. So it goes.

Re: Oil seals: Define "good."

I can't believe there is only one place on the island that sells bearings and seals? Now if it was the size of martha's vineyard maybe. Look around some more check google.when you go to the auto parts store have them check the paper catalogs right in front of you bring the old seal and measure it with a set of calipers for the sizes, and do some camparisons in the catalog they can't do that from a puter, and young kids don't even want to try.jim

Re: Oil seals: Define "good."

A. J. Souza /

Yeah, I know. It sounds odd, but even my old moped shop gets its bearings from the same place when they used to do my Magnum repairs. (I guess the seals too.) I am just wondering if the auto parts guys get them from the same source too? Seems weird though that with a million-plus population, there is just one shop listed, but that was the cost for each seal and the 6203 bearing was over $9.00 each.

Re: Oil seals: Define "good."

Oil seals last a long time and even 30 years ago they didn't get brittle. On a two stroke motor like most mopeds or snow-mobiles etc the proper test is to make seals (plates and gaskets etc) to plug the intake and exhaust holes.) then put the piston at the bottom and apply not more than 15 psi of air pressure in the spark plug hole. Sounds like a lot of bother to me and I have been a motorcycle mechanic for 40 years on BSA NORTON, H.D. Yamaha and mobylette. If the main bearings are bad then even new seals will not seal. But if seals are leaking then you should be able to see the leak. On any two stroke motor Chainsaw etc a leak will make the motor hard to start and it will not idle good because it will suck air in through the seal easier than through the carb and will not get enough fuel (gas) to operate. This is called a lean mixture and it is simply not enough gas for the air. When you do get the motor running it will race too fast but maybe die as you open the throttle . A rare case is where the motor backfired and the excess pressure blew the oil seal part way out but maybe sucked it part way back in, it still leaks.

Re: Oil seals: Define "good."

Re: Oil seals: Define "good."

A. J. Souza /

Thanks to E.E. for precision answer. And Jim, ironically, it's Maguire who charges $6.25 for those seals each. Never heard of the other guys, though.

Also, I was told repeatedly by numerous guys (they all assured me it was the case!!!) that the Magnum and Maxi brake cables were interchangeable, but your's isn't? (Saw your other query.)

Re: Oil seals: Define "good."

Ben Van Zoest /

EE, thanks for the tips, appreciated by all...

Re: Oil seals: Define "good."

Yeah it's only the rear brake cable that's interchangable between the maxi and magnum also the throttle and clutch cable seem to work for both, but the front brake cable is longer for the magnum. The screw barrel at the wheel end is longer than the maxis' the cable casing is longer than the maxis' and the inner cable is also longer than the maxis' it's imposible to fit the maxis' cable to the magnum with the longer magnum mkII forks.I know that the part numers are different the maxi uses cable #910.8.18.003.0 where tha magnum uses #910.8.18.005.0 hth.Jim

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