what could be wrong here lads

5 replies to this topic
  • madmanuk

Posted October 05, 2002 - 12:15 AM


when i pull my throttal back quick it don't respond fast enough, infact somtimes the bike just dies, its ok when the revs are high, So :) could it be lack of fuel or somthin like that.

  • MN_Kevin

Posted October 05, 2002 - 01:42 AM


accelerator pump sending excessive amount of fuel into your carb throat >> floods out your engine with fuel.

Do the "BK" mod to it.

  • yamaha.dude

Posted October 05, 2002 - 10:55 AM


If you don't want to or can't do the BK mod, then learn to roll the throttle on not snap it open... you can play will all sorts of jetting combinations, but like Kevin says, the Accelerator Pump is temporarily flooding your engine...


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  • madmanuk

Posted October 06, 2002 - 09:33 PM


Thanks but whats the BK mod :)

  • sabin

Posted October 06, 2002 - 10:46 PM


Use the SEARCH function, it's your best friend
Check out Motoman393 (God speed him) web site. It helped me with my BK mod.

  • yamaha.dude

Posted October 06, 2002 - 11:04 PM


The BK mod is basically a simple modification of your carb to reduce the fuel pump squirt to less than 1 second, Some bikes have a squirt duration of 3 seconds or more... and when you pump the throttle, the engine has to swallow all this fuel, and as engines like to have lean conditions to increase their revs, this is not good.

Having the pumper carb is good for throttle response, if it is set correctly. Do not twist the throttle when the engine is not running, you will flood the bike - do not let kids get on your bike and twist the throttle, you will have a hard time starting the bike... if you 'need' a competitive advantage in a race, twist the other guys throttle a few times...

Look at the motoman website for some hints on doing the mod. There have been a couple of variations, Taffy did a nice version...

Good luck,



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