My spark plugs were always turning black (slightly wet) even on a lean-ish carb. After new piston rings, crank seals, clean air filter and carb and electrical inspection it still fouled plugs, the bike still started first kick with choke and ran fine. Then when i checked the plug once i measured the gap and it was 0.032", after gapping it to the recommended 0.020" the bike sounded leaner without actually adjusting the carb. Can a incorrect spark plug gap rich foul plugs?, i have always thought that the larger the gap the hotter the plug will run so why would it rich foul???

Edited December 27, 201312 yr by toman21

Yes . Learned that lesson age 17 after my brand new RD 250 E broke down on the way home from picking it up from the bike shop . Supposed to have had PDI (at a cost of £17) and the plug's hadn't been set . If the gaps to wide the spark can't ignite the fuel because it's smothering the electrode .

Edited December 27, 201312 yr by shyted