[HUGE puddle of oil under my 78 YZ80E!]

I put the bike away for the winter about a month ago, was rooting around in the garage this afternoon and happened see a big puddle of oil had spread out from underneath the dropcloth beneath my old 1978 YZ80. The entire contents of the transmission/clutch seem to have leaked out.

I haven't disassembled anything yet but it looks like the oil seal for the driving sprocket has failed (or possibly the gear shift oil seal). Is the oil seal something I can replace from the outside (by removing the sprocket) or will this entail splitting the case? Does anyone have a DIY guide for this? I'm mechanically competent but don't like to get into something without at least some knowledge of how to tackle the problem. Ideally if anyone can point me to a PDF service manual that would be the best.

The bike has been in the family since new, the seals are all original so I guess I can't complain they lasted as long as they did. It looks like I have myself a winter project!

Thanks in advance.

Cheers,

Daryl

i have the same bike and it does the same thing its my shift fork seal, but i have next to zip for compressiona and hae to split the case and do a full rebuild anyway so im just going to replace it when im doing that

[1978 Yz 80E Full Rebuild]

Im starting a rebuild in acouple of weeks of my 78 Yz and i was woundering if there was any percautions or things i should watch out for or make sure i do, or get for it