83 Yamaha XS 650 Misfiring in low rpm.

[locomoto]

Hi:
I have a 1983 Yamaha XS650 Heritage Special. The motorcycle ran perfectly for years, and after being stopped for a month it began to fail, producing misfiring in low RPM, in the left exhaust pipe only. This is when the motorcycle is stopping at a traffic light for example. Once at speed the problem disappears. I have replaced the spark plugs and their cables, the coil, the fuel petcock, and I have cleaned the carburator with Seafoam motor treatment, several times, without disassembling it. The problem continues. Any advice to solve this problem? Thanks.

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[Jan_P]

I believe you have a electronic stock ignition
I believe this is a waste spark system firing both cylinders at the same time.
I would look into switching the left to right and right to left ignition Wires

Se if the misfiring follows the shift getting misfire on right side afterwards.

 

[Adamc]

Sounds like the same problem I have been having:
https://www.xs650.com/threads/what-have-you-done-to-your-xs-today.32082/page-636
Post No: 12,705 onwards

Been chasing the solution to this for months!
If I find it before you I will let you know.
Good luck!

 

[jetmechmarty]

Remove and clean the pilot jet in the carburetor that is misfiring. That should fix it.

 

[Adamc]

Also read my build thread from here:
https://www.xs650.com/threads/welsh-flat-track-revival.60449/page-13

 

[Halftwist]

Sounds like your pilot jet/circuit. Sea foam won’t make a difference on that tiny rascal. Gotta get in there, happy hunting.

 

[locomoto]

Sounds like the same problem I have been having:
https://www.xs650.com/threads/what-have-you-done-to-your-xs-today.32082/page-636
Post No: 12,705 onwards

Been chasing the solution to this for months!
If I find it before you I will let you know.
Good luck!

I can't believe it!!! There are now two of us at least with the same problem...ja I will let you know. Thanks

 

[locomoto]

Thanks for all the answers, I'll work on the problem.

 

[Kevin Werner]

I believe you can adress this without removing the carbs. Drop the float bowls for access. Be very carefull removing your pilots so as not to narf them up.

 

[Roy]

Hi:
I have a 1983 Yamaha XS650 Heritage Special. The motorcycle ran perfectly for years, and after being stopped for a month it began to fail, producing misfiring in low RPM, in the left exhaust pipe only. This is when the motorcycle is stopping at a traffic light for example. Once at speed the problem disappears. I have replaced the spark plugs and their cables, the coil, the fuel petcock, and I have cleaned the carburator with Seafoam motor treatment, several times, without disassembling it. The problem continues. Any advice to solve this problem? Thanks.

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Sounds like you have a tiny speck of something in the pilot jet. Clean the pilot circuit thoroughly with carb cleaner and compressed air.