Working on the carbs for my 83, I followed the manuals (both Yam '83 and Haynes '82) to perform the test for the accelerator pump nozzles, and am not able to get any fuel to come through the nozzles at all. I know that the passages are clear because I carefully cleaned them and blew compressed air through, observing it coming through. The Yam manual says to 'close the larger diameter hole in the pump body with your finger', which took some figuring out but I am confident I got that right. I put fuel in the bowl of the rear carb as directed, and operated the throttle, which is correctly connected to the accelerator pump (note this is an '83 and the accelerator pump set up is not the same as it is on an '82).
Has anyone been able to get this test to work? Any suggestions about what I am doing wrong or where the problem may be?
I know there is a check ball that if I remember right is under the nozzle. Those can get frozen and not allow fuel to pass. Try doing a search for accelerator check ball and see if I am right.
If I recall correctly there is a check ball and a small cylinder of brass that acts as a weight on the ball to help it seal the orifice under it. I have moved on to other carbs, but original carbs can be made to work well if you get them properly sorted.
Thanks for the replies. The problem was a lot stupider: I had the spring in the accelerator pump on the wrong side of the diaphragm. When I put it together correctly, and plugged the line to the nozzle on the front carb, I was able to get fuel out of the the rear nozzle. I've got a leak in the hose connecting the pump to the nozzle on the front carb, which further complicated the test as the system only works when it is sealed. But I did find the root cause of the problem in my lack of attention to detail when putting the pump back together after cleaning. New hose and I will test again to see if the front nozzle is working.