hi folks. i have been putting off lubing the final drive and clutch splines and after watching the related how to on u tube i am wondering about a statement on the video about " the engine rear main seal is not leaking!" , at the point where they had removed enough parts to lube the clutch splines . so if i get in there and notice there is oil leaking what will i have to do at that point and how much more involved will it be? i do have a small leak, a drop a week?, under the transmission/gearbox but i have not pin pointed exactly where it is coming from, it does appear to be engine oil. it is not gear oil from the tear prone rubber boot, one of the first repairs i did to the bike.

Not sure how you are on foreign languages but a quick look at the video HERE will give you an idea

Take a drop of the leaking oil and rub it between your thumb and forefinger. the smell will quickly tell you if it is engine oil or gear oil. The gear oil will have a sulphur odor; engine oil will not. If it is engine oil, it is possible that either the O-ring on the engine output shaft is gone or the main seal is gone. The only way to determine that is to remove the transmission and clutch assembly to take a look. The O-ring does tend to age and shrink, allowing oil to slip by. It is an easy replacement, well documented on this site. Most people replace the main seal once they've gone to the trouble of getting that far into disassembling the drivetrain. The replacement procedure is not very hard, just detailed.

I've just done this. I had engine oil inside the bell housing so something was leaking. I pulled the clutch out and found the clutch plate was almost worn out and behind that the rubber o ring around the main shaft was hard and brittle. It broke into pieces when I tried to get it out. I replaced the main seal, o ring, main nut, clutch plate and clutch bolts and washers. I got a pair of 8mm x 100mm bolts, cut the heads off and used them as locating rods to get the gearbox out/in.

The whole clutch assembly is balanced. The various parts of the clutch must go back in the same way they came out.  
It wasn't that difficult although the clutch assembly needed some persuasion to come out.

ok, thanks ,mates. although i 'm not really looking to taking more things apart after getting the bike back together and riding it some it is nice to know what one might run into on the next mechanical adventure . hah
as soon as i get some lube ordered i'll take a deep breath and give it a go.