I have a 1974 yamaha 250 enduro that fouls plugs every10 miles.?

Question

i've eliminated the autolube and mixed the gas myself so that's not the problem.it has 8000 easy miles on it.besides the rings what else could it be?somebody told me there is a leaky seal in the gearbox and oil is getting in the cylinders.it runs pretty good till it fouls out and yes it's extra smoky too.

Answer 1

Did you check the jetting?  Sounds like you are running rich (more gas and oil entering the combustion chamber than needed, not enough air).

What mix ratio are you using for your gas and oil?

Goosey

Answer 2

Is it for sale ? and how much?

Answer 3

Dirty air filter.

Mix ratio at 32 to 1

Spend 30 minutes to clean carb and jets.

If this does not work, change rings.

Answer 4

Is your choke cable broken with the choke closed?  Check that out.

Answer 5

I had a 73 enduro and fixed a similar problem by rejetting.  If that doesnt help, rings would be my next bet.

Answer 6

Dirty air cleaner.