My 77 400/4 was running erratically and showed black plugs. I removed crabs cleaned thoroughly and replaced all jets and needle valves I got it running but still erratic I balanced the carbs still not running well. I checked inlet rubbers replaced Air filter still no good a local bike mechanic told me to back out the Air screws 1 turn but at that they appear too loose it was also suggested I use a hotter plug. Any ideas or suggestions appreciated.
