When I first got Cyril last year I had him served by the local garage. Just looking at the spark plugs and I see they fitted NGK B5ES plugs. Are these correct? The engine is a 2 lit, T4, CJ engine. The gap is also set at about. 0.85mm which is a bit high looking at Haynes, but Cyril has been starting & generally running fine, approx 21mpg? What is the likely effect of this & do I just leave well alone?
B5ES are absolutely correct for stock motor. NGK are exceedingly reliable and used by just about all the major motorcycle manufacturers.
NGK make excellent plugs. A bigger gap is better as you get a bigger spark, so better ignition. The downside is that you need a higher Voltage to break down the air-fuel mixture between the electrodes as the gap gets bigger, so if the spark is a bit weak it might not be able to jump the gap. If you're running OK at the moment, you've obviously got plenty of juice and so best just to leave it all as it is.
