badly fouled plugs

[marsxs]

After rebuilding the carbs on my '72 xsb, the plugs are fouled with heavy ,black residue after only 25-30 miles. I can't figure out if its low spark or too rich/ lean. I don't want to start randomly replacing coils, voltage regulator, etc..Help!

 

[5twins]

Did you install rebuild kits because many times the included jet sizes are wrong. In particular, the kit for yours contains a generic Y-22 needle that should not be used.

 

[marsxs]

Yea, I used rebuild kits from Mikesxs. I'm going broke buying new plugs. Greatful for any help.

 

[5twins]

If you replaced the needle and seat assemblies then the floats probably need to be reset as well. There's more to rebuilding carbs than just throwing new parts at them, lol. 9 times out of 10, they don't need most of those new parts, just a thorough and proper cleaning, then a proper set-up and adjustment.

 

[XSLeo]

Have you read the carb guide?
Leo

 

[mouser]

Throttle flaps not sealing properly will foul plugs. Worth a check! 1 flap not quite right fouled my left plug forever...till I checked them

 

[CDNTX650]

i agree on the rebuild kit thing....maybe new float valves for a rebuild. Other than that, new Viton orings where needed and throttle shaft seals combined with a complete tear down and cleaning. And getting rid of brass floats on 80 bs34's