My brother has a 1985 YFM 200 and within the last month it has been using an excessive amount of oil (oil is down to the bottom line on the dipstick within 25-30 miles since we changed it). Otherwise it works great, no smoke, no fouled plug, no oil dripping on the ground. I have no idea where it's going. The only oily spot I see on the motor is the left side of the cylinder. Any ideas what could be going on?

 

If its not leaking out of the motor, and not going out of the exhaust, then it could be going down into the shaft drive. Check your rear differential level and make sure the fluid is not too runny, engine oil is thinner than the rearend fluid.

 

Thanks. I'll check that this afternoon. I did find a piece of what looked like gasket material in the screen when I changed the oil.

 

I'm quite sure now that the head gasket is the problem. After driving it last night there is a lot of oil on the left side and the front of the motor below the seam between the head and cylinder. Hopefully that is all it is.
Also, does anyone know what that black thing is sticking out of the back of the cylinder? I assume it's a vent of some kind but the manual doesn't mention it anywhere.

 

Just keep this in mind, from full on the dipstick to the 1st line would be around 1/2 quart of oil, and it only takes a few ounces of oil to make a BIG mess. The oil could be going several places. Hopefully the leaking gaskets is all it is.

The black thing on the back of the engine is your cam chain tensioner. It has a sping in it to automatically keep your cam chain tight as the chain stretches.

 

That black thing is your timing chain hole, dont mess with it unless it needs to be, and the lever on the right side of the cylinder, which i found out recently, is a decrompression lever. Works wounders when you font have eletrical start working lol

 

I just picked up a head gasket for it and hope to change it this week. I was really surprised that a genuine Yamaha gasket was still available. Does anyone know what the head bolts should be torqued to?