How does the accelerator pump...
Posted February 04, 2002 - 07:24 AM
Posted February 04, 2002 - 07:58 AM
If you are at constant throttle, the AP does nothing.
The BK mod reduces the amount of fuel sprayed into the throat of the carb. Why is this necessary you ask? > The amount of spray is excessive causing an overly rich, flooding condiition.
The APJ makes up for the lack of response that the lower vacuum causes. It gives an immediate surge of fuel into the engine, so engine RPM's & vacuum can increase and draw the fuel into the carb.
Posted February 04, 2002 - 10:06 PM
The pump consists, more or less, of the following parts: two springs, an arm, a rod, a diaphragm, pump housing and pump jet.
When you open the throttle the slide pulley releases the first spring which pushes the arm, which is connected to the rod, which depresses the diaphragm, which forces fuel through the pump jet (which is located inside the carb throat just behind the slide). The BK mod acts as a stop on the aforementioned arm, cutting the pump’s operation short. W/out the mod the pump’s capacity is limited by the volume of the housing, once you open the throttle it will deliver fuel only until it runs out. The pump will not refill until the throttle is released.
When you close the throttle the slide pulley rotates the arm and rewinds the first spring, lifting the rod and allowing the second spring, sitting underneath the diaphragm, to push it back up, refilling the pump via a circuit into the fuel bowl (this circuit has a check valve in it permitting fuel to flow in only).
Hope this helps.
Posted February 04, 2002 - 03:05 PM
The jury is still out re:BK on 2002 bikes, even Mr. BK say's the 02's don't need it. So I'm watching this subject very closely. I don't seem to have any low speed bog since going YZ timing, at this point I think I will pass. But it is nice to have a detailed explanation.
Posted February 04, 2002 - 04:19 PM
I think I am going to go for it.