SOHC.co.uk Forums > CB750

Running rich

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adrian58:
Sorry meant to say 1and 4 share the same coil. :P

adrian58:
Sorry screwed  todays  first post up. It's 1+4 plugs wet and sooty 2+3 ok and as they use the same coil thinking that could be cause. Brain fried after the started gear saga. :-*

hairygit:
Okay, so it probably IS ignition related. I have no experience of boyer ignitions other than taking them off and binning them and refitting points plates, but you may want to have a look at your coils/leads before blaming the boyer.

adrian58:
Wondering if maybe it's the plug caps. The No4 one has been changed at some time. Anyone else had probs with the coils or plug caps ? Am I right in guessing they are resistor caps ?

hairygit:
If you suspect the ht caps, (unlikely 2 would fail together) try replacing them, but I'm more inclined to suspect the coil, or the wiring to it. Pop the tank off and have a good look at the coils themselves (looking for cracks or anything leaking from them) the security of the ht leads into the coils, and particularly the low tension wiring to the coil (corrosion in the bullet connectors can cause a lot of difficult to trace hassle, and check the connection is tight) If you don't see anything obvious, try swapping the low tension leads to the opposie coils (the blue wire to the yellow and vice versa, and use the ht leads that are currently on cyl 2+3 on 1+4 and vice versa. If the problem moves to cyls 2+3 it's got to be an ignition system fault,so put the wiring back to how you started, then you need to think about borrowing a coil to try, if the problem goes away, happy days, you need a replacement coil, if not, then start to suspect the boyer :( (I'm assuming you've already checked the wiring fron the points cover to the coils for continuity, particularly the join at the back of the motor, that joint is well known for being a pain in the arse!)

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