Topic: Plug Conditions- 2 Rich/2 Not Bad

[Popwood]

It's a stock '75 750K. Wanted to check milage so determined today getting just below 34 mpg. Not great given the kind of riding a do. So tonight I pulled the plugs and find both 1 and 4 black with soot while 2 and 3 seem much closer to normal for about 1000 miles. So if I'm running rich on 1 and 4, where should I start with correcting the problem? I'm thinking maybe timing? I'm pretty sure the valves are set OK. Last summer I did a complete tune-up including carb sync. Air filter replaced last summer too. Here's a photo, not the best but I think you can see the difference. I'm holding them in order.

[eurban]

1-4 and 2-3 are paired in the ignition system.  It is suspicious that your issues are also so paired.  I would suggest that you look to the ignition first.

[Popwood]

So, eurban, start with points/timing and check coils?

[eurban]

Yes.  Coil failure is less likely but possible.  Also, look at the wiring to the coils and points.  You can compare spark output between the 1-4 pairs and the 2-3 pairs by removing the plugs, and holding one at time next to the engine while turning the bike over.  You should notice a difference in the quality of spark between 2-3 and 1-4 if your problem is ignition related.