if youve got a fcr, and a bog, check your ap timing screw!

ok, just put a 39mm FCR on my 400 ex, and it ran good unless you nailed it, would pop and choke and die like none other. so I went to do the BK mod, and noticed that I couldnt even manually push the pump linkage, so I started playing wtih it and noticed that I had to pull it the other way to draw the linkage out and then when I let go it would spray, because the timing screw was so far out it would let the accelerator pump be depressed almost fully at idle. so I turned in the screw in all the way so that with the slide closed the pump would actually be primed and reay to fire. also drilled and tapped it for my bk mod screw. left this all the way out. put the carb back on the quad, started it up and revved it a few times to make sure the ap circuit was full of fuel. then shut it off, looked down the throat and nailed it and the timing was too quick, barely sprayed the beginning of the slide, so i backed the screw back out til it missed the slide. started it back up and just messed with my duration adj. screw I added and got it to run SO much better. I can nail it now no problem. still every now and then it I stab it from idle as fast as I can it coughs, but not usually. and if I BARELY bring it above idle and nail it its perfect every time. before it would run liek crap even if I nailed it form about 1/4 throttle.

the jetting is still off at 50/170 but I am tuning the carb tomorrow when I go riding for real.

would you mind posting some pics of how you did this? and do you need the BK mod to do it?

heres a good thing to read.

Tuning the Keihin Accelerator Pump, Part 1
http://www.thumpertalk.com/forum/sho...or+pump+tuning

Tuning the Keihin Accelerator Pump, Part 2
http://www.thumpertalk.com/forum/sho...or+pump+tuning

Tuning the Keihin Accelerator Pump, Part 3
http://www.thumpertalk.com/forum/sho...or+pump+tuning

and just to make sure the pump sprays at all or misses the slide then no the mod isnt required, its helpful if your pump sprays too much when you nail it, of course larger leak jets let it spray less. to do it though take the access cover off to get toyour throttle rotor, and watch it as you push the thumb throttle, and see the other 2 little levers that turn also, theres the metal one which is in direct contact with the throttle rotor, and the black plastic one is spring loaded to the metal one, so when you nail it you should watch the metal one pull away from the plastic one and then the plastic one slowly catch up to it. the screw with the spring on it is the timng screw, more in makes the pump spray sooner, mine was so far out that when idling with no throttle the black linkage was already jjust about fully depressed so when i nailed it it had no travle left and sprayed no fuel.

thanks for the info, i'd been wanting to adjust the a/p for a whil, but couldnt get some straight answers. thanks a bunch!

Quote:

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Originally Posted by maddmatt02

the screw with the spring on it is the timng screw, more in makes the pump spray sooner, mine was so far out that when idling with no throttle the black linkage was already jjust about fully depressed so when i nailed it it had no travle left and sprayed no fuel.

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Excellent! Exactly what I needed to know. I have a little play in my throttle cables, should there be zero play?