HI all , I have been looking for a fix to this problem for nearly a year . The problem was , the Number 1 cylinder was fowling the plug , running very Black and sooty , and the other 3 were running fine . I did all the usual checks , but it took a new mechanic [ old school ] to find the cause . I had just got him to fit a Dyna Electronic ignition , check valve clearances , and give the carbs the once over [ digital Vacum Guage ] . He said he couldn't think of any reason for the sooty plug , and I was just wheeling my bike out of his shop and he said hold up a minute and he screwed out the air mixture screw out of carb no 1 . He found that the end of the mixture screw had snapped off , due to being screwed in too far and hard . So I rode home in torrential rain a very very happy man , with the task of getting the broken tip out the carby in front of me . I removed the mixture screw when I got home and I looked down the mixture hole where the screw had been and could see the broken tip in the bottom of the hole . I removed the airbox and found I could get a small flat screw driver in the passage that led to the airscrew hole from the back of the carb . It also gave access to the tip of my high pressure air nozzel . I tried blowing it out , no good , also tried to pry it out carefully with the small screw driver , but where the problem lies here is that the tip sits in a recess that goes past the vent tube that I could get the screw driver in . I them got out my Dremel and used 3 small [ bigger each time ] drill bits and very very carefully drilled the top of the brass broken tip . After a nerve wracking few minutes the broken tip just came loose and I was able to blow it out with compressed air out the Mixture screw hole . No metal fragments can go in your engine as long as you use compressed air to keep blowing the brass fillings out from the back of the carb . I installed a new mixture screw , set it the same as the other carbs and the bike is running better than it ever has . No more plug fowling , hesitating as I throttle on , running great at last . I noticed that there were others here with the same problem and they also were unable to find the cause .
The pics show the broken mixture screw and a complete one , the hole at the back of the carb , where I inserted the air nozel and the airmixture screw in place . Hope this really helps some of you here out , also let me know if you had found the same problem .
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