Triumphrat

quagmire · 06-09-2008

What's a comprable Champion plug for an NGK B8ES?

bendavanza · 06-09-2008

N5 is too hot.
Most likely your fouling problems come from worn out needle jets.
They wear quickly and will contribute to sooty plugs.
Most 650 twins call for N3 and 500's N4 (unit). I forget what the 750's use but N5 is probably too hot. I used to do the same thing to "help out" bikes in need of tuning but I know better now.
I've never liked NGK plugs on old brit bikes, Champions work great for me.
New Bonnevilles are a completely different story.
-Ben

htown16 · 06-10-2008

Quagmire,
NGK and Champion plugs are not directly equivalent. A B8 is slightly cooler than an N3 and a B7 is between a N3 and a N4. N3 is what Triumph recommended for all 650's and 750's up til the mid 1978 model year when the T140E was introduced. The factory then issued a service bulletin recommending that N5 be used in the T140E's. The difference is the head design of the T140E's which do better with a hotter plug. If your bike has splayed intake ports run the N3's. If it has parallel ports run the N5's. As far as NGK 's, if you do a lot of in town riding and short trips, the B7 is probably a better replacement for the N3 than the B8, as it is less prone to fouling. If you do a lot of high speeds or sustained highway work the B8 might be the better choice.
Htown

quagmire · 06-10-2008

I've noticed I've had some fouling issues on the right side. Left side looks good. The Triumph manual says the right side runs richer than the left on the TR6's, but I thought a change in plugs would be worth a try so I'll get some N3's and see.

hobbit · 06-11-2008

Interestingly enough, originally the T140 was rated for B8ES, but I've noticed that even NGK themselves recommend B6ES now. Perhaps something to do with modern fuel formulation?