Hello, this is my first post on this forum, and I’m very sorry for asking this question, but I’m desperate.
Three months ago, I got my Yamaha XJN 600 (1999). The previous owner said that the bike had been sitting unused for about two years. When I started riding it, I noticed it was stuttering and losing power.
At home, I bought a second-hand coil pack that connects to two pistons (if I remember correctly, cylinders 2 and 3), but it didn’t solve the problem.
This is only my second bike and I have no mechanical skills, so I took it to a mechanic. The bike stayed there for three months. They told me they cleaned the carbs, replaced most of the rubbers and O-rings inside the carbs, and changed the fuel pipes that connect to the carbs. But the bike still has the same problem, and they don’t know what the issue is.
The problem consists of 2 middle cylinders don't warm up and bike losses a lot of power (mechanics did a pressure test on the pistons and they said they were all good)
I live on a small group of islands in Portugal, so access to mechanics is very limited. I don’t want to just send the bike to the junkyard, so I decided to take matters into my own hands.
I would really appreciate any help in figuring out what the problem could be. Again, I don’t have much knowledge in this area, but I’m open to learning.
