Motorcycle Forum / General / Yamaha / May 2007

Hi all,

I have a 1980 XS 650 sidecar rig in need of some diagnostic expertise.
Cutting to the case.....it runs at idle, but will not rev beyond idle.  It
just falls flat on its face.  Burbles, pops, spits.  The problem started
about 5 miles after filling the tank. Cleared up briefly, than reverted back
to the not running above idle.  I drained the tank and put in fresh gas.  I
pulled the carbs X2 and cleaned them to no avail.  I replaced the CDI unit
suspecting there was a problem with the ignition not advancing. I have had a
CDI unit puke before causing intermittent problems. .  I can pull either
plug wire and the revs drop, from idle, the same amount.  What ever the
problem is, it effects both cylinders equally.  I see a strong spark at the
plug at idle, and it weakens as I attempt to rev the engine.  I have cleaned
the plugs and tried a fresh battery.  Actually, I run it off a car battery
in the sidecar trunk. Coil, perhaps?  Also, I do not think there is a
problem with the tank petcock.  I tried running the bike with the petcock
set in the prime position.  Any help much appreciated.  I cannot afford to
take it to a shop, but I really would like to get the beast running again.
FYI,  here is a link to pictures of the rig.
http://webpages.charter.net/clickfam/pictures.htm

Thanks,

Ron
www.mondo-ron.com