T500 Center Seals Change or Not

[Vintageman]

Hello,
How many people changed the Center seals on their T500 project? Well should I say how many did not and had no issues.
The T500 like the T350/T/GT250 uses the Crankcase oil to lube center bearing. So if the seal is a slight bit week the engine smokes due to crankcase oil leaking through.

Even if you use smokeless oil and engine is warmed etc. it can smoke if bad. I see some youtube videos and these bikes are smoking even running warm and steady. (Maybe not smokeless oil... etc.). I don't want the green police to throw me in jail for life. I use smokeless oil on my other bikes and no issue when warm .

My T350 does not smoke now (I did not change center seal either. I used a more sleazy but reliable solution... made it get lube form mixture like a Yamaha RD)

Maybe the T500 had a more reliable seals then the T350. My T350 I tried two cranks both had a bad center seals (hard to tell by looking for they seem OK, just leak a bit). These were bad and the crankcase oil would get low. Ran well just always smoking

Sure just change them I suppose, but this is not cheap for the crank needs to dissembled. I do think I found someone with the experience, but still expensive and a always risk due to complexity.

My T500 motorcycle has 6800 miles real clean inside no water damage. Maybe there is a way to check. I currently have cases split for had an issue with kick starter pawl. Time to have it changed is now, but not sure if it is necessary and don’t have a money tree.

Thanks

[dinogt]

It is not a km problem, it is a problem of oldy.
Seals are goods 10 Years (without sun), after, you must not put it in a motor.
The stingers in the seal are olds and the "rubber" become more and more hard, with out flexibility.
The diameter became bigger and sealing goes in hollydays.
It is only when the seal diameter too big that the motor smoke too much... but before the motor drink the box oil with out excessive smoke.
A too hard seal used also the crankshaft.
Don't think you can found an old motor with old good seal, it is impossible.

[Vintageman]

dinogt.

I believe you are saying must change. No way it can be good based on age Anyone else have any luck as is?

I think the fact the center bearing uses the gear oil even if it leaks a little it will cause bike to smoke all the time.

Interested to here others on this too.


Thanks

[geck0]

If you have the motor apart and you think there was a seal leak than have the crank rebuilt. Seals are about $80 but the rebuild should be done by a qualified person. There are two that I know of The Crank master is in Connecticut. and Bill Bune in Minnesota.

I have had a motor that sat for 10 years and ran fine when it was called up to the majors. This was back before ethanol was added to the gas. Now a motor that sits may be less apt to run well after sitting for years.

[Vintageman]

gecko,

I don't know if it needs changing. I wish I did. The Right one looks absolutely perfect and is soft. I suppose I could try it as is. But if it smokes, always, then I bet it leaks some. How many use the smokeless JASCO FD rated oils? It really works from what I see once bike is warm. No smoke leaves any of my bikes when cruising, where as before it did. (But the invisible exhaust fumes due to unspent gas can choke anyone following... I pull over and let them pass particularly if the air is heavy.)

I hear Crank master is good and all he does is Suz. Still pricey if not needed. Always a risk too (Have heard horror posts about such work done)

I need to save some $ and suppose just do it.

I was curious how may had not changed (I imagine several people have not) and felt they were OK (low smoking). I had bad luck with T350 (center bearing oiled by gear oil like T500), but all my other bikes have original seals and run perfect as I see it.

[dinogt]

One thing, if externals seal are dead... why central seal must be good ?
If some one change only external after a leak seal... ask him how many km or miles has he do without central seals problem.

[tz375]

On Yamaha twins we used to find that the primary drive side was typically still soft, and the dry alternator side was typically very dry and hard.

I can't extrapolate my small sample of a few motors to suggest that all crank seals that stayed oiled would be OK. They may be OK but I would replace them because if they are dry, then the damage to barrels pistons and crank could be much higher than the cost of replacing them now.

[relic]

Why not pressure test and be certain? I use a comprssion tester adapter, the pump from a blood pressure tester and an old fuel pump pressure guage.
With the motor somewhat assembled, make a block off plate that seals the intake, (held in place with the boot mount nuts/studs. Make similar to seal the exhaust.
Pressurize the motor and watch the guage. If it does not hold 8psi or so then look and listen for the leak. Spray soapy water on the outer seals and watch for bubbles.
If the outers are good, listen at the oil fill hole for leakage from the inners. Check each cylinder individually.
Also check your apparatus for leaks before condemming seals.
You may not be able to "hear" the inners leak but if all else tests ok than that has to be the problem.
Relic
.

[relic]

Here's a pic testing my GT500. Doesn't show my block offs but does give an idea of the pressure tester.





Relic

[tz375]

Good points relic and that's a nice simple tester. We use a Motion Pro unit because I was given it by an ex racer I supported who was also sponsored by Motion Pro. It's really well made but a touch expensive to test just one bike.

Your solution looks good.

[titan performance]

I think I have been really fortunate, as I have never experienced seal failure. I've fired up a couple of motors that have lain dormant for 15 years or so without problems. I have worked on the principal, that, once it's in the frame...if it runs without a problem...then all is well and good. But if it's oily, then to take it back out and pull it down is no major job, and can be done in a couple of hours. No big deal.

[geck0]

You may not be able to "hear" the inners leak but if all else tests ok than that has to be the problem.
Relic
.

I suspected an inner seal leak on a T500 motor back in the 90s. I worked with a local small engine repair guy. We did a leak down test and it wouldn't hold pressure. It would weep very slow. but couldn't prove that it was a seal until I covered the vent with a balloon. as soon as the pressure started to drop the balloon started to fill. I said "Yup a bad seal" I dissembled the motor and saw a spot on the motor halves that separated the gear section from the crank. It looked discolored a bit. I brought it back to that repair guy and he agreed it could be the smoking gun and what the hell rebuild the motor and try it again. I put it back together, did the test and crossed my fingers. This time no drop in pressure. "never jump to conclusions"

[dinogt]

i think we can do with by another way.
Put off the cylinders, put air pressure by the breather and hear near the cranckshaft... or put gazoline... to know if there is air leak

[Vintageman]

The T500, T350 early t/GT250 for example use the crankcase oil to lube center bearings. It even kind of pushes it through via gears gogs so a bit a pressure there as well I imagine pushing oil by any weekness in sealing ability.

If the center seal(s) leaks even a bit you really may not know a performance lean issue but is smokes too much all the time. Had this issue on a GT250. after some time you may note case oil goes down. The other bikes like GT380 or 550 or 185 or later 250 use the oil pump to lube cnters so I think one can get a way with a little leaking stiff seal and not smoke out pipe either if one uses the right pump setting and smokes oil for example (i.e JASCO FD)

Not sure if the T500 center seals was as sensitive.

Don't want to ride a bike always sending smoke when cruising along.

I suppose I need to change to be proactive or do a leaks tests.

It sounds like many 500 owners do not worry and theirs have been fine running, but do they smoke all the time?

Good replies on how to do a leak test.

But still want to here how many "Had" to change center seals and if not do they think their bike smokes too much or not.

I only fixed center seals on my t350/gt250. Did not touch my GT380, 550 or 185, Non smoke when cruising. But fully not until I switched to smokeless oil as stated. They run fine too no lean issues to date and many hard miles to show so far.

[tz375]

Are you asking for facts or for opinions? The question asked appears to be tell me who thought they needed to change the seals and whether you think it smokes too much. That's asking for opinions without a frame of reference. I may think my newly rebuilt bike smokes too much and you may think you old bike with clapped out seals is fine.

My opinion is of zero value to anyone under those circumstances unless there's some sort of frame of reference.

If you don't want to change crank seals, that's your call.