4th character would be A - 'SH 267 A5' corresponds to a 1985-86 'Tiger High Arch' model.
Which isn't consistent with the LHS snorkel fitment.
For a definitive answer, we need the actual engine number. Which is stamped on the side of the crankcase, on the carby side. So you'll likely need to squirt a bit of degreaser around to see it.
Cheers,
Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
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