DarylS

Thanks Khunangkaro, well said. I was going to post something similar but you beat me to it. So... Does anybody know where I can view the PDF version of the Factory Service Manual? I know there is a Clymer manual available (Clymer Yamaha YZ50-80 Monoshock 1978-1990, ISBN: 9780892874958) but I've never much cared for Clymer or Haynes as they are never as good as what the factory issues. I suppose in a pinch though the Clymer manual is better than nothing! Can anybody help? Thanks folks. Daryl

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

Hi Paul, Thanks for the advice. It IS a rubber Inlet Manifold so I took the carb off today to get a good look, the inlet manifold seemed fine. On re-assembly I used silicone grease to help seal the carb-to-manifold junction in case there was a flaw that I didn't see. Unfortunately I have the same behaviour. The "WD40 trick" didn't work either. The only way to reduce revs is to use the kill switch as before. Any suggestions what else I can look into? Is there anything in the carb itself that could be stuck or clogged? I haven't taken it apart yet but am thinking on giving it a good deep clean to see if that will fix the problem. Also, with 20+ years of storage there may be some internal seals and such that may have dried out. Wish me luck finding parts if that's the case! Cheers, Daryl

Hi All, I'm fixing up my old 1978 YZ-80 for my son. It will make a great new-to-him ride just as soon as I get it back into running trim. The fork oil is 31+ years old and I have a sneaky hunch that it probably could use a change. I don't have the service manual so am hoping somebody can advise me on the following: - What is the recommended change procedure? - What's the recommended viscosity fork oil to use? - What's the oil capacity of each fork? The fork seals seem OK, they are not leaking despite their age. TIA for the replies! Daryl

Hi All, By hook, crook, and otherwise I managed to hang onto my first ever bike. It's a 1978 YZ-80 that I bought brand new when I was 12. After spending 20+ years hiding in the garage I pulled the bike out of hibernation, put some gas/oil in the tank and after about 20 kicks it fired up, beautiful! My 9-year old son is now anxious to try "Dad's old bike" out for himself. It will make a great restoration project. There's some obvious parts the bike needs (tires, chain & sprockets, brake pads, rear swingarm bushing etc.) but need some advice from the group, hence this posting. I put the bike away properly way back when I stored it (drained tank & float bowl, fogged the cylinder through the spark plug hole etc). that's why it started OK for me. I did say I fired it up, but the idle isn't stable. It starts up fine but the revs never "drop" when you lift off the throttle. So if you blip the throttle to say 5000 RPM the engine STAYS at 5000 RPM till you hit the kill switch. When you restart it the revs are normal until you rev the engine again. What's really weird is that if you press the kill switch only long enough till the revs drop, then flick the switch back over before the engine stops the engine will maintain the revs at whatever speed the engine was spinning when the spark came back on. Any idea's what the problem could be? TIA! Daryl