Correct Spark Plug For '72 Oif T120v

Just had a look on www.triumphrat.net and the general concensus of opinion seems to be that the B8s are too cold and will foul up at any opportunity. B7s are hotter and B6s are hotter still and will therefore both be less prone to fouling. If it was me, I would try the B7s and check the colour of them after a 'spirited' run (cut the motor and coast to a halt before checking). If they still look a bit sooty then try the B6s, which seem to be the plug of choice for most people, but not all - a few seem happy with B8s. Bikes of that age may well by now have different requirements after a lifetime of abuse. Just remember that going to a hotter plug can cause a piston to hole which is why I would just go up one grade at a time. Buying two sets of plugs is a cheaper fix compared to replacing a piston. Please don't ask me how I know this .... and anyway, it was a Norton, m'lud.
Also check that the carbs/air filters are ok and that the ignition system is functioning as it should.

 

Only bike I ever had where I didn't leave home without a spare set of plugs and a plug spanner

 

This might help with the plug grade madness

http://www.briskusa.com/spark_plug_cross_reference_heat_range_chart

 

I have the same problem with my T140 powered Triton and have got Denso 20's (hotter) in at the moment having read somewhere (online) they were a better plug but have also ran a Champion 6 and NGK 8 both colder with varying results HTH it drives me nuts!

 

Very true that @rich, I'd forgotten that bit

 

My first bike, a Suzuki 50cc Sportsman, took great delight in 'whiskering' its one and only spark plug. This was when petrol was leaded and the lead built up on the plug and gradually closed the gap between the electrodes (at least, that's what I have always been lead to believe - lead ... geddit? Oh please yourselves). This was a nuisance, but at the ripe old age of 16 I just didn't care and carried a spare plug or two with me and got the defunct plug(s) sand blasted at the local bike emporium (Ewbanks, Pontefract, mid sixties!) each Saturday ready for the new week. Didn't know any better really. Ah the innocence of youth!! Soon learnt though.

 

Pretty sure it was a B reg i.e. 1964, bought new by my brother who later decided a car was more useful to him for carrying his fishing tackle (he bought an Austin A35 would you believe!!?). I think I paid him £60 for it, about 3 months before my 16th birthday in September '66.
Yorkshire has always been at the cutting edge tha knows.
Yes I know, sorry about that. I don't do jokes, but loonyism comes naturally!

 

Back in the 70s I always went with bs6 for the t120 but that was back in the day with proper petrol

 

http://raskcycle.com/techtip/page139.html
HTH