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obxnc

BK Mod theory??

7 posts in this topic

Alright, I did the BK Mod to my 01 426. Turned it down to a split second dribble instead of the 15 foot, 3 second long stream. Now, how exactly is this supposed to get rid of the bog? Basically all I did was turn off the accelerator pump, or seriously turn it down. What is the theory behind turning down the duration of the AP?

I did the mod, and went out and rode. I did notice a slight difference in throttle response :thumbsup: , but nothing major :thumbsup: . I did not adjust it any further than the initial adjustment though. Should it get rid of the bog on a throttle blip or just help out in the acceleration around corners?

I guess I was expecting a mind boggling difference.

A little insight please... :bonk:

The light blue wire mod is next.. Or should I just leave it alone??

Thanks all... 70-75 this Thursday (perfect riding day) :bonk:

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http://m.bobbitt.home.comcast.net/yz426fm/tech/ap1.jpg

Now that is also dealing with leak jets that you do NOT have in the 426. So the BK mod is kind of doing the same thing as the leak jets, just in a different way.

Now since you have the BK mod done, you need to finish jetting the carb. Get a longer fuel screw and JD Jet kit. Do that an you will have no bog at all.

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The imfamous "bog" can be caused by either too much fuel being injected by the accelerator pump, too little fuel, or improper timing (too early or too late). When you have too much, you get kind of a stumble when you crack the throttle, too little and it just starves for fuel with a dead spot. It seems the 250F's mostly suffered from too little squirt and a lot of 426's suffered from too much.

It sounds like it did the job for you. You are not going to see a mind boggling difference on a 426. Some folks think that if they can twist the throttle from zero to full throttle without hesitation while the bike sits on the stand, they have it tuned properly. This is not always achievable and certainly not required.

There is mountains of discussion in the TT archives on the merits of proper accelerator pump action. I personally have tuned my son's and my 250F with smaller leak jets and have achieved good results.

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The imfamous "bog" can be caused by either too much fuel being injected by the accelerator pump, too little fuel, or improper timing (too early or too late). When you have too much, you get kind of a stumble when you crack the throttle, too little and it just starves for fuel with a dead spot. It seems the 250F's mostly suffered from too little squirt and a lot of 426's suffered from too much.

It sounds like it did the job for you. You are not going to see a mind boggling difference on a 426. Some folks think that if they can twist the throttle from zero to full throttle without hesitation while the bike sits on the stand, they have it tuned properly. This is not always achievable and certainly not required.

There is mountains of discussion in the TT archives on the merits of proper accelerator pump action. I personally have tuned my son's and my 250F with smaller leak jets and have achieved good results.

That about says it all! Lessening the pump shot also minimizes flooding and starting issues. Who cares about what happens on the stand, can you get it to bog in gear under load while in the correct gear for that speed? If not, ride on.

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That about says it all! Lessening the pump shot also minimizes flooding and starting issues. Who cares about what happens on the stand, can you get it to bog in gear under load while in the correct gear for that speed? If not, ride on.

Finally somone says the obvious ! I was starting to worry that I wasn't riding hard enough because I never experienced "the bog" while actually riding the bike !

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That about says it all! Lessening the pump shot also minimizes flooding and starting issues. Who cares about what happens on the stand, can you get it to bog in gear under load while in the correct gear for that speed? If not, ride on.

Finally someone states the obvious ! I was starting to worry that I wasn't riding hard enough because I never experienced "the bog" while actually riding the bike !

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Thanks for all of the quick responses.. I guess I will try messing with it and see what the difference between no AP shot and a full AP squirt. Then find the happy medium with the best results and go from there.. I do understand the possibilities of the flooding at the factory settings (man that was alot of gas!!)

If nothing else, this is an awesome forum with tons of great information..

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