AC pump timing


I do not have a ’99, but I believe the tab controls the timing of the pump relative to throttle position, but does not change the total stroke.

The rod is now further along at closed throttle, but I believe the total amount it will travel as you open the throttle should be the same. So you have advanced the timing of the squirt but not shortened the stroke.

This was covered by JD in an older post that I guess dropped off into the abyss, because I couldn’t find it...

...but I do remember talking to Sudco about the tab, the standard gap is a known quantity and is something that road bike tuners (big customers of Sudco’s) manipulate to improve throttle response. Point being they are a good source of information about this setting on your carb (Sudco 800-998-3529).

I have been experimenting with the bendable metal stopper / tab on my '99's throttle disc ( where the cables attach and touch the black plastic lever for the AC pump ) I recently pryed it closed about .015'' which is half way. This in turn reduces the AC diaphram push rod to about 3/32'' travel. Throttle response seems better and I may even go with 1/16'' stroke. Is this set-up in line with the very popular BK mod on the '00 models on up?


I've been messing with the same thing on my 99yz. It seems to help alot. I've also made a bracket that restricts the length of the throw of the AC pump rod. Basically it does the same thing as the BK mod. It bolts on to the bottom of the pump itself and extends up to the AC pump arm where a screw limits the travel. The response is much better so far. I need to try a different needle. Its deffinately worth doing.


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