Help me diagnose my black sparkplugs

[estcstm3]

Hi all,

Still new to wrenching on my bike. I pulled my sparkplugs and they are pretty black. From reading the manual it looks like I need to run a "hotter" sparkplug, but I dont know that means. Anyways here are some pics of my sparkplug, hopefully you all can tell me whats going on. The bike runs, but my battery is being wonky, I just had to refill the cell with distilled water as they were drying out....but other than the low voltage on my batter I can kick it over. Bendix gear is worn so its kick only at the moment.

1975 xs650b

 

[5twins]

You don't run a hotter than specified spark plug. You find the cause of the black plugs and fix it. You should be running BP7ES spark plugs. If you're running 8's then yes, that's a step too cold and would run darker in color. Get some 7's.

 

[webbrs]

Read through the carb guide and check your floats to make sure they are spec., after you know what plugs your running. I think your carb is +/- .5 mm. that is very touchy and too rich is easy to be. (yoda impression)

 

[wherearewe]

Have a good read of the carb guide in the tech section. Get a handle on your setup (what plugs you have, how old, carb type, jet sizes, float setting, air filter and exhaust mods. If its all according to spec and there a still problems, you will at least have the information needed to help members of the forum help you. Or something to that effect.

 

[estcstm3]

So to take this up a level, the issue with my plugs would be from my carb? Im assuming my bike is running rich. Hoping there were some "low" hanging fruit items to review without taking apart my carbs.

 

[webbrs]

Unfortunately correct me if I am wrong, but, your carb set doesn't have the drain nipples that the bs34's have. You could use the clear tube to check fuel level if you did. I hate to assume but your not complaining of any running/leaking issues as of yet and your machine looks stock if your avatar is of your machine. So jetting doesn't really come to mind unless you bought the machine recently from a much different altitude or climate. In that vein would float height change? if the float needle has worn or the pin is loose maybe. .5 mm isn't much room for error. your air filters are clear and clean? Your spark plug gaps are correct? if all is true then maybe a worn jet needle or float valve tip. You might be able to adjust the mix but that's really only a fine tune. Varnish or trapped gunk would lean it out seems to me. I am knee deep in carbs right now myself and if you have to go into them, I can only say this, read read read... ask ask ask and do only one change at a time. maybe do some idle plug chops then some mid-range and full throttle chops to see if you can narrow down which circuit is the richest. you will need to mark your throttle for a more consistent read, and need new plugs, best to have new ones for all the ranges. good luck and let us know.