Center Oil seal on T500 - how does it pull oil in?

[Rocket350]

I got my bike running after she's been sleeping for 14 years and was able to take it around the block. In the meantime I've been reading a lot on this site and have learned about the dreaded center seal that sucks in tranny fluid if it goes out. I ordered the two outer seals since I know the left one is leaking. I doubt a leak down will tell me anything until I get the outer seal replaced. But in the meantime I'm trying to understand HOW it would pull in tranny oil if the crankcase is casted seperatly from the gearbox resivour. I keep looking at pictures from eBay to understand the case better but I just can't seem to understand and the few pictures don't tell me much. All I can come up with is it would leak between the horazontal halves of the case. Sorry, I don't want to sound dumb but I like understanding how things work - or malfunction in this case.

[Alan H]

A leaky centre seal won't pull transmission oil, but will affect tbe other cylinder. If your outer seals are shot, it's odds on the inners are too. The problem with old 2 strokes left stood for a long time is that the seals go hard and the face that it runs on goes rusty, so when you run the engine, the seal gets rubbed away, then leaks. The only cure then, is to replace the seals and clean the seal faces on the crankshaft. I filled the crankcases on my gt550 with diesel before I ran it and turned it steadily many times, then flushed the diesel out. Worked ok, and still fine after about 3000 miles.

[Rocket350]

OK that makes complete sense. What would be the symptoms if the center seal is worn? How does it effect the engine and performance?

[Alan H]

Poor starting, poor running, poor power, poor most things really as some of the charge goes into the other crankcase.
If you know anyone with a good engine, try theirs and compare. The difference will be noticeable.

[Rocket350]

So after more research and looking at pictures the oil schematic in the service manual it looks like the tranny oil is what feeds the center bearing on the crank and if the seals go bad it will allow the oil from the transmission to seep into the crankcase. I'm not sure if my seals are bad but it does smoke a lot. But I have not had it nice and hot to burn all the crap out from the leaky needle seats. Still waiting on those and outer seals before she gets ridden hard for a few miles.

[dinogt]

if you have 1 old seal dead, the others seals are also dead, + or - but dead and wrong.
If you are waiting for too much smoke with oil box, it will be surely bad for your gear box, at first the 5°... and the 4°...

[Pete O'Dell]

bit of a late reply.

yes worn centre seals will use gearbox oil as will a r/h outer, it will start and run quite happily if all else is well but will smoke like a battleship laying down smoke.

there are several ways this happens, seals old and hard and as allan says wear away, but usually the seal sticks to the crank and the lips either tear or due to the seals shrinking a little when they get hard either spin in the bearing or the oil actually just leaks past the outer edge between the seal and bearing.