faber
XS400 Enthusiast
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Hey guys,
So I'm very frustrated with this bike. I cannot seem to solve this run away / slow to return to idle issue. I've changed out jetting, restricted airflow, gone through the carbs, verified no leaks, etc, etc.
The only thing I can think of is that the TCI/CDI unit is faulty, have any of you experienced this?
On start up when cold it starts with full choke only, once started it races up to 4500 RPM, if I kill the bike and turn it back on quickly (just a quick blip on the kill switch) the RPM drops as it should, back down to idle and it idles nicely there until you touch the throttle again.
Once the bike warms up it's either slow to rev up, or idle back down. I've gone through 20+ jetting combo's and the only thing I can think at this point is the CDI unit is failing (which I've seen many times on honda's). I'm really getting to the point of where I'm thinking of just ripping the bike (title in hand) apart and parting it out.
Thoughts?
Bike details:
This is the spoked wheel version with the drum front and rear.
1982 xs400 special II with TCI/CDI (not mechanical timing)
BS34 carbs, currently with pods, had the original filters on it, made no difference
Not sure which combo of jetting I've currently got in it, but it's running rich, when it was running right, or lean it still had this run away throttle / slow to idle down problem.
Rebuilt carbs from the ground up, replaced everything except diaphragms which looked fine, and passed leak down test
compression is a little low at ~116 on each side.
Vacuum line is good connecting to rebuilt diaphragm petcock, other side is plugged, carbs are vacuum balanced.
So I'm very frustrated with this bike. I cannot seem to solve this run away / slow to return to idle issue. I've changed out jetting, restricted airflow, gone through the carbs, verified no leaks, etc, etc.
The only thing I can think of is that the TCI/CDI unit is faulty, have any of you experienced this?
On start up when cold it starts with full choke only, once started it races up to 4500 RPM, if I kill the bike and turn it back on quickly (just a quick blip on the kill switch) the RPM drops as it should, back down to idle and it idles nicely there until you touch the throttle again.
Once the bike warms up it's either slow to rev up, or idle back down. I've gone through 20+ jetting combo's and the only thing I can think at this point is the CDI unit is failing (which I've seen many times on honda's). I'm really getting to the point of where I'm thinking of just ripping the bike (title in hand) apart and parting it out.
Thoughts?
Bike details:
This is the spoked wheel version with the drum front and rear.
1982 xs400 special II with TCI/CDI (not mechanical timing)
BS34 carbs, currently with pods, had the original filters on it, made no difference
Not sure which combo of jetting I've currently got in it, but it's running rich, when it was running right, or lean it still had this run away throttle / slow to idle down problem.
Rebuilt carbs from the ground up, replaced everything except diaphragms which looked fine, and passed leak down test
compression is a little low at ~116 on each side.
Vacuum line is good connecting to rebuilt diaphragm petcock, other side is plugged, carbs are vacuum balanced.
Last edited: