I bought a non-running 1980 Yamaha XS400 in showroom condition for $600, and have gotten new sparkplugs, fresh gas, did a once over on the carbs, and sprayed starting fluid into the carbs. The bike still won't start. So, after buying a compression kit, I checked both cylinders with the throttle open. Left cylinder had 90 PSI, right cylinder had 80 PSI. In addition, when I was testing the right cylinder, I heard a weird noise from I believe the right cylinder, like a tch, tch, tch sound, possibly air escaping? Now onto my question.
What components on these bikes are more susceptible to failure that would cause low compression? As far as I know, the previous owner didn't adjust the valve timing or complete a ring job before I bought it. Also, I've read about putting oil or atf into the cylinder and letting it sit for a few hours to improve the compression, has anyone had luck with that on these bikes? Again, it was ridden last year then stopped running and started backfiring, and has been sitting in an enclosed storage unit for the past 9 months.
What components on these bikes are more susceptible to failure that would cause low compression? As far as I know, the previous owner didn't adjust the valve timing or complete a ring job before I bought it. Also, I've read about putting oil or atf into the cylinder and letting it sit for a few hours to improve the compression, has anyone had luck with that on these bikes? Again, it was ridden last year then stopped running and started backfiring, and has been sitting in an enclosed storage unit for the past 9 months.
