Hi everyone I am new to the forum. Looks like a great place to learn. I live in Vancouver BC Canada and I just bought a 1981 XS 400 Special II, this will be my first official motorcycle although I also own a 2003 yamaha BWS (zuma) 49cc scooter. I posted some questions about the motorcycle last week after I went to see it and one of the cylinders was dead. The previous owner took it to a shop where they determined that the spark plug wire was all corroded, so they replaced it and when I went back to see it again it was running nice and smooth with lots of exhuast comming out of the tailpipe. I decided to buy it.

The next day I started playing around with the bike and I noticed that the exhuast pipe on the suspect side was still cold after running for a long time. I pulled the plug and it was covered in oil residue. I noticed a small puddle of oil had collected on the inner lip of the muffler so I cleaned it all up. I took the bike for a 15 min spin and when i got back I noticed that their was more oil in the muffler lip. I am assuming now that the cylinder not running strong is from oil getting in to the combustion chamber.

My question is where is the oil possibly comming from? Is it a huge task and expense to rubuild these motors? When I drove the bike around it seemed to have lots of power and idled nice. Any help would be great. Thanks

to the forum

Could be a head gasket that's gone south.......or your valve guides have seen better days......would be my 1st assumption.

Either way, it sounds like a top-end refresh could do wonders.....not too difficult really.....as long as you're familiar with a wrench & have a decent manual.....it should be a reasonably affordable fix.

mmm, if that side isn't firing, maybe oil is getting past the rings?

if its not been run for a while, the oil control ring can gum up letting oil get past into the cylinder

Hi everyone I am new to the forum. Looks like a great place to learn. I live in Vancouver BC Canada and I just bought a 1981 XS 400 Special II, this will be my first official motorcycle although I also own a 2003 yamaha BWS (zuma) 49cc scooter. I posted some questions about the motorcycle last week after I went to see it and one of the cylinders was dead. The previous owner took it to a shop where they determined that the spark plug wire was all corroded, so they replaced it and when I went back to see it again it was running nice and smooth with lots of exhuast comming out of the tailpipe. I decided to buy it.

The next day I started playing around with the bike and I noticed that the exhuast pipe on the suspect side was still cold after running for a long time. I pulled the plug and it was covered in oil residue. I noticed a small puddle of oil had collected on the inner lip of the muffler so I cleaned it all up. I took the bike for a 15 min spin and when i got back I noticed that their was more oil in the muffler lip. I am assuming now that the cylinder not running strong is from oil getting in to the combustion chamber.

My question is where is the oil possibly comming from? Is it a huge task and expense to rubuild these motors? When I drove the bike around it seemed to have lots of power and idled nice. Any help would be great. Thanks

Hi there,

is the residue oil or a shed load of unburnt fuel ? To confim this do a dry compression test followed by a wet one this should give you a good idea to the state of the engine without having to strip it. If this turns out OK then look at the service items i.e. Dwell, timing,tappits & carbs.

Regards Jim