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Post by trippleduce on Feb 27, 2005 9:06:36 GMT -5
I have a 1978 sr500 that was not running for about 5 years, helpfull people worked on the carb and of course messed with the pump rod on the accel pump. when I got the bike it would start but then immediately die. I replaced all jets with stock and then replaced the diaphrams. no change in starting. found the the pump rod had been adjusted. after 15 to 20 kicks the bike would run, pushing up on the accel. lever caused the bike to idle smoothly, and I adjusted the pump accordingly. the bike now starts with 1 to 2 kicks. My question is "How is the correct adjustment determined?" I see that the fuel switch is controled by carb vaccum, would I use the vaccum to set the pump rod like I would if I was tuning the carb on a older auto.
Thanks for your help.
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Post by batmanron on Mar 3, 2005 16:32:32 GMT -5
Hi Trippleduce
The Pump rod should not be involved in the starting process on the minuki carb. You will find once you have set your pilot jet idle screw to 1 1/4 to 1 3/4 from closed and the float level is set right it should start with one or two kicks. 20 kicks is way too many to be kicking a high compression 500 single, hope your saving up for that knee replacement surgery.
The Pump Rod, and I like the name, is only there to give an initial squirt of fuel into the engine when opening the throtle from the idle position, to assist in not stalling the bike with an initial large rush of air. The xt and tt500 run a carby with no fuel pump as such and it is not really needed - just another way for yamaha to sell spare parts when the diaframs wear out.
On newer large singles this "stalling, air rush problem" is reduced by the addition of a boost bottle. This is a non crushable bottle, not unlike a kids drink bottle that is attached to the intake manifold. this bottle remains under vacume on idle and sucks air in to become at near atmospheric conditions when the bike is under throttle.
Thumping Downunder
Batmanron
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