Okay guys I’m finally getting ready to give up on this bike unless any of y’all can solve this one. It’s a 1980 XS400 special. Sat in a garage for most of its life, only 6,000 miles on it.
Im having a serious left cylinder constantly rich and right cylinder constantly lean problem. Which creates really poor running conditions. At this point I’m fairly confident I’ve gone through every single possible issue...
Starting with:
Carbs - I’ve tried THREE different carbs on the bike now. The original mikuni BS34 I totally cleaned, bought new and set ALL jets and screws to factor settings.
LEAKS -
-I’ve replaced the carb boots on the head, and I’ve made sure the exhaust pipes have been fitted down tightly. I’m confident there is no vacuum leak.
Valves
I have set the valves to factor positions. BOTH chambers get phenomenal compression. Upwards of 150psi.
Timing:
The bike is a SPECIAL 2 - which means it has an electronic ignition system, and is much more difficult to reset. I’ve set the timing the best I can to the point where it seems to run pretty consistently but I don’t think that would be a huge contributor to my problem.
Coils and ignition system
I’m getting good strong spark out both coils, I’ve tested the altornor, rectifier, all in working order. The system includes an “igniter unit” which I don’t know how to test, but I have no reason to believe that is the problem.
I honestly don’t know what else to try. Any help will be greatly appreciated before I finally decide to just pass it on.
Thanks
Im having a serious left cylinder constantly rich and right cylinder constantly lean problem. Which creates really poor running conditions. At this point I’m fairly confident I’ve gone through every single possible issue...
Starting with:
Carbs - I’ve tried THREE different carbs on the bike now. The original mikuni BS34 I totally cleaned, bought new and set ALL jets and screws to factor settings.
- through out the course of these I played with various pilot screw adjustments, float height veriations, including butterfly adjustments.
- I’ve pretty much concluded it’s not the carbs.. this has been a CONSTANT issue no matter how I adjust the carbs - even if I wanted to get right cylinder running rich I can’t.
LEAKS -
-I’ve replaced the carb boots on the head, and I’ve made sure the exhaust pipes have been fitted down tightly. I’m confident there is no vacuum leak.
Valves
I have set the valves to factor positions. BOTH chambers get phenomenal compression. Upwards of 150psi.
Timing:
The bike is a SPECIAL 2 - which means it has an electronic ignition system, and is much more difficult to reset. I’ve set the timing the best I can to the point where it seems to run pretty consistently but I don’t think that would be a huge contributor to my problem.
Coils and ignition system
I’m getting good strong spark out both coils, I’ve tested the altornor, rectifier, all in working order. The system includes an “igniter unit” which I don’t know how to test, but I have no reason to believe that is the problem.
I honestly don’t know what else to try. Any help will be greatly appreciated before I finally decide to just pass it on.
Thanks
Attachments
Last edited: