Another BK mod complete

I just did the BK mod - The gas sprayed from 3.5 seconds to about .4 seconds now ... The timing of the spray with the slide was perfect. Stock jetting, fuel screw is out

1 3/4 turns - My bike started up easy but after a ride, it felt no different than before the modification.

Maybe I'm missing something or my bike was good before ... What's your take?

(2001 YZ426)

You really only notice a difference in sudden throttle changes. Like coming out of a corner hard. It's not a night and day thing and you do not get more HP out of it. Just a crisper throttle response.

I rode my freinds bike that does not have the mod and mine back to back and the hit out of the corner was the thing I noticed. Mine hit harder and he had a 50 sprocket on the rear.



01 YZ426F #85 Vet C

Don't be discouraged - My 2001 426 also ran good before the BK mod but generally seems a slight bit "cleaner" on low end response. I believe this mod helps more for the bikes that experience the "bog" on the bottom end. I'm at 1/34 on the fuel screw and have also moved to a 168 Main which seemed to liven up the top end.

Thanks for the responses ...

I posted here a couple of weeks ago about how my bike fouled like 8 plugs - would run good one day on a new plug and would run like crap the next ... I played with the jetting a bit to lean up the bottom but have since went back to stock and for whatever reason, my bike has run awesome for 4-5 rides and counting.

The only difference is that I am running my idle pretty high - and I did the BK mod yesterday.

Make sure you increase the main jet. Remember that the APJ was squirting fuel for 2-4 seconds before, even at WOT. You need to replace that lost fuel or the bike will run lean and lose power. At least the bike wont go lean on you after the 2-4 second squirt is up.

Mike, I have the stock main jet in (162?)

My bike didn't feel lean but I'll check the plug also ... What main jet is everyone else using?

I run the 162. But, I was running a 158 with the BK mod. I use 50/50 race fuel(Sunco 110) and pump gas(chevron 93) and I am at sea level. So, I can run leanner on the jets.

I would say try larger jets and see what happens.



01 YZ426F #85 Vet C

I read that Brian Kinney (BK) says to run a 168 (he must mean at standard conditions). This equates to a 162 for me at 5K ft ASL.

Sea level runs bigger jets than those at higher altitude.

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