Bk mod?

I'm new to the site and new to this valve thing but can someone explain this mod and if so does it work on the 520 MXC? Forgive the newbee with lots 'o questions.


It seems the bk mod is only for yamaha FCR carbs, although the ktm and yamaha both have a FCR carb, the linkage is somewhat different. That mod effectively shortens (or limits) the stroke of the pump linkage by using a screw and spring, our linkage will not work for this mod, however, if you feel that your pump is spraying too much gas in. You can get the p-38 pump housing from factory R&D which also shortens the stroke, but is not adjustable ($80)

one thing to check though, my 01 400/EXC came with a pump diaphram with a "stop" on the gas side to shorten the stroke, when the diaphram failed, I ordered a replacement from KTM, the new one had the same part number, however it did not have the "stop", I figured it must have been an updated part, but now it is spraying a constant stream of gas, as it goes completely through it's stroke with nothing to stop it. I am waiting to here back from holeshot ktm about this.diaphram.jpg

[ November 06, 2001: Message edited by: katoom300 ]

Hey katoom300 could you please post those results on this page or email them to me.

I am very interested in this because my 2000 400 has the same stopper.

Have you tried the new diaphram yet?

If so, How did it work?

Did it make a differance?


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