- Sep 9, 2003
The problem I am having with Norton Commando 850 MK2A interstate 1975 is the plugs seem to be black all the time, I have tried all settings form the manual but am unable to get the rusty brown colour it should be. The bike has peashooter exhausts, no balance pipe between exhausts and the black box air filter behind the Amal MK1 carbs, I also use Castrol Valvemaster additive in the petrol. The throttle needles are set in the top groove so it is in its lowest position. The bike also pops through the exhaust if the mixture is weakened too much to try to get the right colour. I intend to check the compressions incase there is wear on the valve guides and the bike is sucking air, the timing has recently been done and is spot on and the carbs have been stripped with new gaskets and have all the correct jets fitted. Can you tell me if I am following the right lines here?