Octane Question

GoldenMotor.com

marioaz

New Member
Dec 15, 2008
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Prescott, Arizona
Breaking in a new GT-4. NGK B6HS. Smaller plug gap, .020-.025 had the top end clanging and rattling. Predetonation? Re-gapped to .030 to retard the timing, and most of metallic rattling has ceased but bike a little slower on run up. Using Shell 87 octane. Does higher octane affect these engines as far as predetonation goes?
Grubee instructions plug gap is .036?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,837
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up north now
Octane will have little to no effect on these. They have around 6.5 to 1 compression. I would look to the wrist pin for the clatter.