Topic: Accelerator Pump Question

[Rosinante]

Still working on tuning this bike, which is getting better, but right now the throttle is REALLY sensitive at slow engine speeds.  That is, when starting from a stop, or when going very slow in first, the slightest twist of the throttle increases power dramatically.  It takes some skill to drive in this condition because it does not want to deliver a smooth increase in power in these conditions.  Power comes ON at the slightest twist.  So here is my question:

When the accelerator pump arm linkage mechanism is adjusted correctly, is it designed to NOT pump fuel at these low speeds and near-closed throttle positions?  Yes, I know i should remove the carbs and clean them and follow all the adjustment specs and reinstall but first, should I suspect accelerator pump linkage adjustment problems given these conditions?

[Don R]

 That sounds like a race throttle tube may have been installed. They react quickly.

[Tracksnblades1]

Do you know what rpm your mechanical advance comes in at?
Sometimes an accelerator pump can mask a lean mixture resulting in an erratic throttle transition. Similar to a stumble followed by a surge.