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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Looking down into the plug the porcelain looks good at part throttle and color change in the ground strap indicates good timing.. What I don't like it's how lean it is at idle. Where I marked up the white ring should have some soot/carbon build up not white..
unleaded fuel can burn with little deposits
not uncommon on computer controlled systems
if you look at the gm system, at idle, it leans it out till the point of miss fire and then the computer adjusts, reason why the engine has a miss that you cannot find. it is a little trick they use to pass epa since most emissions are at idle and speeds below 40 mph.
engine condition also plays a part as miles add up. not like the old carbs.
if work has been done and no compensation and the computer cannot adjust then the issue becomes ugly. also failing sensors.
Looking down into the plug the porcelain looks good at part throttle and color change in the ground strap indicates good timing.. What I don't like it's how lean it is at idle. Where I marked up the white ring should have some soot/carbon build up not white..
Hey 98hotrod,
Thanks for sharing.
Can you still read plugs effectively with today's premium unleaded fuel?
I know there is a sticky thread on plugs, but could you point out which parts of the plug itself refers to how the bike is running and also what they should ideally look like?
I have a carby bike and will be attempting to tune it myself by reading the plugs once the build is done.
Thanks.
Hey, this is one of the plugs I cut away to check the burn.. As the rpms go up so does the depth of the burn trace on the plug.. Usually at idle you will see carbon deposits on the ring of the thread section of the spark plug.. As heat builds in the combustion chamber it will leave deposits on the porcelain.. The tip of the porcelain would be the lower rpm range, the middle would be above 3000 rpm, mid, and all the way up would be higher temps/higher rpm's.. wot.. The plug shown I thought was a very good example of good AFR'S..
Hey, this is one of the plugs I cut away to check the burn.. As the rpms go up so does the depth of the burn trace on the plug.. Usually at idle you will see carbon deposits on the ring of the thread section of the spark plug.. As heat builds in the combustion chamber it will leave deposits on the porcelain.. The tip of the porcelain would be the lower rpm range, the middle would be above 3000 rpm, mid, and all the way up would be higher temps/higher rpm's.. wot.. The plug shown I thought was a very good example of good AFR'S..
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