stuartross109 wrote on 12/31/69 at 16:00:07:Hi
Could be a build up of carbon in the engine. The heat retained in this can continue to ignite the petrol even when there is no spark.
May be worth a quick look inside the exhaust outlet to see what it looks like. Also is plug looking sooty, this would indicate a rich mixture.
I have an 86 model which is runnning very rich possibly die to a worn needle jet. See my post for the details.
If the mixture looks OK a good blast at high revs with a good qaulity, high octane petrol may burn off the coke.
Stu
o-ring around the needle valve's valve BODY. not the float needle, just the o-ring around the brass that inserts into the carb's body.
Part number 19's o-ring is worn smooth with the brass into which it's set.
If you don't replace that o-ring, in 2-4 months your carb will start overflowing. You will, shortly thereafter, drain 9 quarts of oil out of your engine. Then you'll get really, really p1ssed the f8ck off. And scratch your head and swear. A lot.
Just replace that o-ring. The needle float is the same as the one for a Harley's bs40, or at least close enough that it works.