Bk Mod Question

How are you guys getting the Bk mod timed to 0.5 sec. Could you tell me the procedure or lead me in the right direction. Thanks Fella's


I was wandering the same. I guess maybe there is some hardware to do it, but my idea is if you have digital video camera, you can film it, playback frame by frame, divide 1 sec to 24 ot 25 frames per second (depends on the camera) and calculate the time...

A stopwatch and good coordination.

Make sure you point the squirt away from your face, twist the throttle open rapidly while pushing the stopwatch button then when the squirt stops stop the watch. Do it a few times and take the most consistent time. It will most likely require some fine tuning when you ride, so as long as you get it in the general area of .5sec it should be alright.

Adjust the screw on your BK mod for a short quick pulse of fuel. From closed to wide open throttle look for the pulse.

Hey guys, Do I have to take the sub-frame off off or any other part of the rear bike? Am I looking in the back side of the carb?(The opening to the aairbox) And finally are you doing this with the bike running or off? Sorry for all the questions just want to do it right the first time :)

You can do it with the carb on (set the spray length) and the subframe off, or with the carb off (and fuel in the float bowl).

Go to motoman393.thumpertalk.com for details.

Thanks skthom2320, I went to motoman393 website and it wasnt very clear if the bike was running while I was doing the test or off. If the bike is off and I whack the throttle wont it be a b@*tch to start again? :)

Pull the carb away from the motor when you do the spray tests. Loosen the clamp where the carb fits into the rubber boot on the head and pull the carb back out of the boot. Let it hang there. It should hang there with the bottom opening of the carb slightly below the bottom of the boot. Place a rag on your motor to catch the fuel that the carb will spray . This will avoid you filling your motor up with fuel as you twist the throttle to check spray duration. Stand behind the carb and look down the throat. Twist the throttle and check spray duration.

Also be sure to adjust your spray timing screw so that the spray just misses your slide when opened. Be aware that everytime you adjust the timing screw, it will affect the spray duration. You may have to readjust the screw you installed to achieve your desired spray duration.

Thanks Wyatt, Much better sense now. Does anybody lock the screw down with glue or locktite so it doesnt move while your riding?

I put teflon tape on the threads of the screw so that it would have resistance to turning. (the same type of teflon you use on plumbing joints.etc.) This will keep it from moving due to vibration.

glad to help...

Ya know I find it extremely hard to believe that anyone has actually time the thing using a stop watch. If the have then they are 99.9999% faster in reaction time then anyone in the world.

The average reaction time is .5 seconds on average (I think)

So if you are holding a stop watch, Looking at the pump at the same time, Turn the excel pump to time. It is virtually impossible to set this at .03 seconds.

I laugh everytime I see that post "I got mine at .05 or .03 or .01

Gimme a break.

So you hold the watch in your left or right hand most likely your non dominant hand. You are using your dominant hand to twist the throttle or turn the pump cam.

At the same time eyeballing the slide.

Yup I can see the exact measurement there of .03 Yup I can. makes perfect sense to me...

Yet another dribbling none informative post by ego

LOL. You got that right EGO, I don't even know what mine is timed to. I just messed with the srew when I was riding until I had the best results. :)

It is virtually impossible to set this at .03 seconds.

I would agree. But you are getting the decimal point in the wrong place. See motoman's website - BK's quote is:

. Then set the duration of the spray to .3 seconds with the adjustment screw you just installed.

That's about a third of a second. 10 times more than 3 hundredths of a second.

Does anyone have any other idea, different from digital video camera?

eyeball the thing, see this post on suggeted method I use and it works


.0 here a .00 there here a dot there a dot nothing more then dot dot Old mcdotted had a bk e i e i o :D

But still it is virtually impossible to set this with a stop watch or any other means at .3 or .5, If you can I want to see a video, this means you have reflexes like a cyborg

Thanks for pointing out my blunder, glad dont work on the space shuttle :)

Setting up the GBmod

I just performed the BK mod today. After I had E.G.O.**** adjust the timing of the "squirt," the bike fired right up, did not have the off idle bog, even when still cold. Normally when cold it would have stalled a couple of times if I gave it some gas. Rolling the throttle seemed to have a smoother transition from part-mid-full throttle. I still have to give it a test ride up in the "hills." My Vortip fell apart, so I'm running with my stock exhaust plug for now.

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