johne67
XS650 Enthusiast
Some Background: I have a 1980 650, which came with Mikuni VM 34's and straight pipes. I replaced the TCI ignition with a Hughs Handbuilt complete PMA/CDI Ignition. I adjusted the cam chain tensioner, then the valves. I followed the Carb Guide with respect to jetting my carbs including the above steps and set the ignition timing with a timing light.
The HHB ignition worked great, and my bike would start with a single kick every time, even when cold. Only problem was that the chokes needed to be on for the bike to start and idle. Switched to a 27.5 pilot and the bike started and idled nicely. Once the bike idled nice, I set the mixture screws using the dead cylinder method. I then put some brand new plugs in and let it idle for a while. Then I shut it down and read the plugs, left side plug was brown, maybe slightly lean but close. The right plug was pure white, as if it was a brand new plug, no discoloration at all, none.
I figured the right cylinder must be running way too lean so I really richened it with the mixture screw and let it run to see if the plug would show a rich condition. But, it was still white like brand new.
While fiddling with the carbs I put my finger next the exhaust to see if the amount/pressure coming out was the same, and it was. Except, I noticed that my finger would get sucked into/toward the exhaust in intervals that make me think it was happening on the intake strokes. The exhaust that's taking in air is the right side cylinder, same cylinder that is persistently lean.
I guess its worth revisiting the valves, but I'm 99% sure I adjusted them properly. Am I correct in assuming that this sounds like a top end job with new valves and/or seats?
The HHB ignition worked great, and my bike would start with a single kick every time, even when cold. Only problem was that the chokes needed to be on for the bike to start and idle. Switched to a 27.5 pilot and the bike started and idled nicely. Once the bike idled nice, I set the mixture screws using the dead cylinder method. I then put some brand new plugs in and let it idle for a while. Then I shut it down and read the plugs, left side plug was brown, maybe slightly lean but close. The right plug was pure white, as if it was a brand new plug, no discoloration at all, none.
I figured the right cylinder must be running way too lean so I really richened it with the mixture screw and let it run to see if the plug would show a rich condition. But, it was still white like brand new.
While fiddling with the carbs I put my finger next the exhaust to see if the amount/pressure coming out was the same, and it was. Except, I noticed that my finger would get sucked into/toward the exhaust in intervals that make me think it was happening on the intake strokes. The exhaust that's taking in air is the right side cylinder, same cylinder that is persistently lean.
I guess its worth revisiting the valves, but I'm 99% sure I adjusted them properly. Am I correct in assuming that this sounds like a top end job with new valves and/or seats?