Plug, or mixture problem

Hi John,

An easy way to check you`r plugs/mixture is to swap the plugsround, or try a different make. e.g. Champion.

Ken Routledge.

Previously wrote:

I recently did a "head job" (no obscene comments please!) on my '54 Dommy 88. After a brisk run, I checked the plugs (NGK B6 HS). The r/h plug was a healthy light brown colour, but the l/h light grey. Since there is no way, with a single carb, to adjust the fuel mixture exactly to each cylinder, what do I try next? Should I run slightly rich, which might soot up the r/h plug, or try a different grade plug on the l/h side?

P.S. I DON'T want to change the bike for a Manxman! John.

hello. John No you do not, It will pull your arms out! And it will be to powerfull for you , Only trouble is, You have a hard job finding one too ,As for your Spark plug why not try Tim Green , at greensparkplug.co.uk or phone 01477 532317 ask of tim ! hope this may help you john .And check your timing 30% btdc fully advanced , and check of air leaks in the manifold !

Mixture bias in manifolds is common,or used to be before mpefi.Matching both branches of the intake might cure it,check for casting flashes or roughness.Running rich is the classic cure,mixture adjusted to suit the weakest cylinder.Regards John.

BSA used to list an angled spacer for the carb which would turn it a few degrees left or right to cure bias problems. If all else fail, you could make one. I presume Norton never produced one because Nortons would never get mixture bias...

Gordon.