Fishwwc
XS400 Member
Hey everyone, my name is Michael and this is my first post on the very informative XS400 forum. A buddy of mine recently gave me his 1981 Yamaha XS400 Special II. He was moving away from the LA area and didn't want to take a non operational bike along with him.
I piddled around with the non starting bike for about 6 months doing bits of research, acquiring service manuals and trying to figure out where to begin with this seemingly overwhelming project. I didn't know where to begin, whether to check the spark plug gap, carb cleaning, points gap, battery, charging system, compression, etc.
I decided that I needed professional help so I had a bright idea to get an internship with a classic motorcycle shop so I could learn first hand about motorcycle diagnosis, troubleshooting and maintenance. I scored a summer internship and it's been going great so far. I've learned more in the past two weeks then the last 6 months of idling around.
I brought my bike into the who and we charged the battery, cleaned the carbs, checked the compression, and adjusted the valves. The bike started right up but made a clanking noise in the engine. When we did the compression test, one cylinder had much higher compression than the other. After rechecking the valve clearance, the mechanics concluded that the clanking noise was from a blown out bearing on the crank shaft. Hindering the right pistons full range of motion, resulting in a lower compression and potentially a lot of work.
Given the situation the mechanics advised that swapping out the engine would be the best course of action. They said it would be a bit more economical and would be a faster track to riding the bike. I could then have an extra engine, to swap out parts, disassemble at my leisure and learn about the engine from the ground up.
So my question to the forum is what other XS400 engines will be compatible with an 81 special II engine. I'm currently looking at a nice 78 engine with very good compression. Any help would be greatly appreciated. Thanks!
I piddled around with the non starting bike for about 6 months doing bits of research, acquiring service manuals and trying to figure out where to begin with this seemingly overwhelming project. I didn't know where to begin, whether to check the spark plug gap, carb cleaning, points gap, battery, charging system, compression, etc.
I decided that I needed professional help so I had a bright idea to get an internship with a classic motorcycle shop so I could learn first hand about motorcycle diagnosis, troubleshooting and maintenance. I scored a summer internship and it's been going great so far. I've learned more in the past two weeks then the last 6 months of idling around.
I brought my bike into the who and we charged the battery, cleaned the carbs, checked the compression, and adjusted the valves. The bike started right up but made a clanking noise in the engine. When we did the compression test, one cylinder had much higher compression than the other. After rechecking the valve clearance, the mechanics concluded that the clanking noise was from a blown out bearing on the crank shaft. Hindering the right pistons full range of motion, resulting in a lower compression and potentially a lot of work.
Given the situation the mechanics advised that swapping out the engine would be the best course of action. They said it would be a bit more economical and would be a faster track to riding the bike. I could then have an extra engine, to swap out parts, disassemble at my leisure and learn about the engine from the ground up.
So my question to the forum is what other XS400 engines will be compatible with an 81 special II engine. I'm currently looking at a nice 78 engine with very good compression. Any help would be greatly appreciated. Thanks!
