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Old 11-30-2012, 08:41 AM   #10 (permalink)
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A vacuum guge would work fine, but you might have to add a small reservoir to dampen the oscillations in the gauge at lower RPM. Most bikes with vacuum petcocks already have a fitting in the intake manifold that you could use for your vacuum source. My 87 Rebel 450 has one as well as the Vulcan 500. A tee off the petcock hose would give you a vacuum source without any other modification.

On a Rebel 250 the petcock is not vacuum operated, so you would have to drill and tap the maifold for a vacuum fitting. The Rebel 250 uses a single carb for both cylinders, so it would provide a more steady vacuum source, but might still need a small reservoir to prevent gauge flutter at lower speeds. Try it both ways and see whish one works well enough for your preference.

regards
Mech
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