Bk mod problems

Seems like the BK mod is the thing to do to fix bog problems and make the 426 start easier. I have a 2000 yz426 and i have added the bk mod adustment screw to the carb, when i looked for the so called spray there is nothing in sight(while cracking the throttle)???? both while the bikes running and while it is off. Seems like a very doumb question but i'm out of ideas, the carbs been all cleaned out.

if anyone can give me better directions on where to be looking for the spary and when(bike on? choked? bike off?), i would greatly appricate it!! or maybe that is my problem no spary? i seem to be running very lean aswell.

Thanks for the help.


Check out thumperfaq.com this web site, it should help. If you remove the air box and boot you should be able to see it when opening up the throttle. The accelerator pump squirts the gas from the right side of the carb throat (the side where throttle cables attach) of the carb towards the engine intake. Hope that helps

The amount of spray is almost invisible unless the carb is off and in your hand. Do not look into the carb throat while turning the linkage. If it doesnt spray, there are a couple of things to look for, cracked or torn accel pump diapragm. linkage jammed or still dirt in a passage. Check them all. It will help if the carb is in your hand and make sure the bowl is full of fuel.


I did the BK mod to my 426. If you take off the sub frame and look into the carb (from where the air box connects) there is a small yellowish/goldish thing sticking up and that is where the squirt comes from. If there is nothing coming from there then your line may be plugged. But I doubt it is. I think your just having trouble finding where it comes from. If you have more questions let me know.


Well thanks for the help guys, that little yellowish jet sticking up was plugged, works great now and man you can really feel the difference with adjusting the new bk mod screw! great improvment, its like a whole new bike. It started good before but even better now!

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