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Remove the timing inspection cap (smaller forwardmost cap on primary cover) to see if the rotor nut has loosened leading rotor contacting/damaging the timing scale. Had that happen once due to a "pro" shop not using the shake proof washer under rotor nut. Also with primary cover removed, check the three screws holding inner primary to crank case. These should have little tabbed washers to secure them but I have had one let go regardless, leading screw flying around primary, damaging chain rollers. Now I always use locktite on these in addition to tabbed washers. Before pulling clutch apart, also check if chain might be rubbing against inner primary. Can happen if inner primary mounting stud is not properly shimmed, casing sitting askew slightly. Backfire could a number of things, carb tuning/condition of jets/needles are a possibility. I had a main jet starting to unwind from carb body giving backfire that got progressively worse over a matter of days. What is condition of spark plug on side that backfires? Is this points of EI ign? Air leaks are carb to manifold or mani to head?
Remove the timing inspection cap (smaller forwardmost cap on primary cover) to see if the rotor nut has loosened leading rotor contacting/damaging the timing scale. Had that happen once due to a "pro" shop not using the shake proof washer under rotor nut.
Also with primary cover removed, check the three screws holding inner primary to crank case. These should have little tabbed washers to secure them but I have had one let go regardless, leading screw flying around primary, damaging chain rollers. Now I always use locktite on these in addition to tabbed washers.
Before pulling clutch apart, also check if chain might be rubbing against inner primary. Can happen if inner primary mounting stud is not properly shimmed, casing sitting askew slightly.
Backfire could a number of things, carb tuning/condition of jets/needles are a possibility. I had a main jet starting to unwind from carb body giving backfire that got progressively worse over a matter of days. What is condition of spark plug on side that backfires? Is this points of EI ign? Air leaks are carb to manifold or mani to head?
