Re: Norton 99

I believe that Norton recommended Champion N5 but many ,including myself,prefer NGK B6ES. For engine oil use a good 20W50 or even better a 15W50. Opie oils web site has lots of helpful information.

How to open a can of worms!. With no info on the year or condition which can have a bearing, I would offer the following. I use vintage plugs made pre 70 actually KLG FE80 because I sometimes suffer fouled plugs and they can be cleaned and re-used on the road not like current manufacture which absorb into the insulator and are made for FI systems. Avoid resistor plugs if a mag is fitted. If the motor wet sumps or burns oil through the valveguides which probably won't have seals then a 40 oil will be easier to live with but will be harder to kickstart cold.I would also say that the only really critical area in a service is the primary case which needs exactly the right amount of non synthetic thin (20)hard to find oil,needs checking for the right amount of slack and has a weird and awkward method of adjustment and needs to be right if you are not going to break chains,ruin bearings and lock up the motor. Welcome to the world of classic Nortons. You could pop into Halfords for a service!!.