gs650 katana 1983

[hitlerspants]

hello,i have a problem where bike only fires on 3 cylinders,this is the second time its happened .first time it ran on only 3,then 2 so i replaced pirana cdi and pick ups with an assured 2nd hand pair.it ran ok for 500 miles and now its gone the same way-only 2 cylinders working-this is an original nippon denso cdi and pick-ups.the only work done to this bike prior to this problem was an original reg/rect. fitted by my mate soon after i bought it.he says he knows what hes doing and hates to admit he might have done anything incorrectly.the coils are fine and its not the leads plugs or ht caps,maybe both cdi s and pick ups were faulty,but if i buy another one i am worried it will go the same way ,it happens gradually over say 500 ish miles

[tom203]

Which cylinders are now not firing? A clue is that 1 and 4 fire together,while 2 and 3 fire together (#1 cylinder is on left as you sit on bike ). When you say "it happens gradually" over 500 miles , do you mean that the power gets worst in increments, rather than all at once?
Also, do you have a voltage meter to check your charging output since you replaced the r/r?