What is this "BK Mod" I've read about here...

Just curious... What is it? I'm a new guy to this forum. Thanks.

Your best bet is to go up to the upper right hand corner of this page and click on search. When the box pops open type BK and hit enter. There are volumes of information in the archives. It'll tell you everything you need to know. There are even some good pictures of it on motoman393's ? Webpage. I think that's his handle.

Here's a link with pictures.

BK modification

Rusty is right - getting to know the search function is real useful. However, I have found that sometimes you get information overload.

Someone needs to make a nice detailed write up and post it in the technical section (in case motoman393's web site goes bye-bye).

Basically you just drill and tap a hole on a tab that is external to the carb. By placing a screw in this tapped hole you can limit the stroke of the accelerator pump and reduce the amount of gas sent through the carb. Evidently the amount is really too much at low revs and causes a bit of a bog when the throttle is wacked. Doing the mod (with proper tuning of the set screw and timing of the stream as described in the volumes of previous threads) will give you instant throttle response like a two-smoke.

It is only possible to do it on the 2000-2002 426s.


Steve T

[ December 26, 2001: Message edited by: YZF426ER ]


My site wont go "bye bye" unless a hacker deletes my account! But I have it all double backed up and it would only take about 30mins to transfer it back if the event ever happened! I dont plan on leaving the MX sport until 50-60 years down the road...so my site will be there awhile.

If you ever see that my site doesnt work the old version is still "intact" on a different server! Here is the link to the old BK mod page (but still has the same info and pics) http://www.scorpius.spaceports.com/~mx393/carb.html Hope this helps,


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