Big Mother Version
Medium Size Standard Version
Legend: Check = check valve (one way flow); Jet = metered device causing restriction of flow, VTV= vacuum transmitting valve like a jet and check valve in parallel.
The secondary throttle on the CB60/61 will not open unless a secondary throttle release dashpot is engaged. The dashpot moves a linkage that engages the secondary throttle and ties it to the main accelerator quad arm.
This diagram shows the basic CB60/61 secondary throttle release schematic. The VTV allows restricted pressure buildup from the carby hat (surge tank), but rapid release of pressure from the line back to the hat when coming off boost or the pressure momentarily drops because the secondary has just opened. The check valve and series jet allow pressure from the manifold to also act slowly on the release, but will not allow line pressure to relieve back to the manifold when it goes into vacuum, once again this is the job of the VTV ( you want the release to hold between gear changes).
Because the action is only to release the secondary throttle to the accelerator there is no regulation in the secondary throttle opening. This will cause the throttle plate to snap open if the accelerator is already floored and the boost pressure is available in the carby hat or in the manifold. This will in turn cause a hesitation, as excessive air is pushed into the manifold before the fuel jet can supply necessary fueling; the engine bogs for a moment. The sudden rush of air will also cause the carby hat pressure to drop suddenly and the dashpot may disengage momentarily.
One way around this is to experiment with the jet, by either removing it or upsizing, so that build pressure in the manifold (via the primary carby barrel) is allowed to also build in the throttle release line at lower revs. However this will still result in throttle snap if the accelerator is floored when driving in race mode, the hesitation nuisance value is up to you.
Another way is to replace the VTV with a check valve, also allowing rapid engagement of the release. Or replace with a check valve and series jet, so that sudden opening of the secondary throttle doesn't cause sudden closing due to momentary loss of carby hat pressure.
So what else to do? Hard question really. You could try rerouting the line from the carby hat back to the discharge of the turbocharger compressor so that the release opens sooner and be less suscepitible to carby hat surges. You could wire the release open, but you may have poor low end performance and certainly heavy fuel consumption.Watch this space for a cure all