BK-Mod, Dirty Carb, Rebuild Kit?

I finally decided to take advantage of the nasty cold weather and do some "winter maintenance" on my bike [00 426]. Actually decided to finally do the BK-Mod. Very simple... and it went without a hitch. Right up until the point I was to "observe the squirt" from the accel pump. Well... it appears that there is nothing coming from my accel pump. So... I pulled the pump off and inspected... a little "worn" but still seems to be pushing. Then I realized the carb was pretty dirty. No problem... clean it right?! Well... I've now been "cleaning" it for 3 days and still can't get a squirt out of the nozzle from the accel pump. Actually can't even get carb cleaner nor compressed air out of the nozzle. Must be all gunked up. Not sure how to get the darn nozzle cleared so the accellerator pump can do its job. Contemplating a soaking in a parts cleaner for a while. I suspect this will damage the rubber parts so I will need a rebuild kit.

Anyone experience similar situation? I know... my fault for letting the carb get this messy... but it was used bike! :cry:

The really cool part... the bike seemed to run pretty darn well. I can't wait to see what it runs like when the carb is actually working like it is supposed to!:cry:

my recommendation is to get a rebuild kit (never bought one so I have no idea what they cost). You are correct...if you soak the parts in carb cleaner it will damage the rubber parts.

My only warning is DO NOT remove the plate that goes between the float bowl and the body of the carb. It's held on by some funny (torx type) screws, they may be painted. I've never done it myself, but from what I have read on here the gasget that goes in there is unobtainable and you'll therefore not be able to get it back together correctly. Maybe someone else can back me up on this.

Not sure how to unclog that thing... actually I'm surprised it ran decent without it! I would have expected major bog (or cut out) when you open the throttle if it wasn't working at all. I'll have to defer to the experts on that one, haven't had to unclog one myself (yet?).

only thing I can see is you placed the diaphram in wrong or it is not seated correctly or you did not put the spring back in.

My question is did you adjust the timeing and squirt duration on the carb?

if you did then most likly you have shut the squirt off completly.

here is a link to the GBmod and a How to write up


Goto http://www.thumperfaq.com/ap.htm and checkout Rick's Tuning the AP Squirt in his jetting guide.

I had the same problem and this helped me dial-in the BK Mod.



If it turns out that I need a rebuild kit... I'll be sure to post where and how much. I've used them on cars [way back when my cars used to have carbs!]


Nope... it's not in backwards, nor parts left out... actually before I started touching anything I wanted to witness the initial squirt of fuel. So all I did was twist the throttle a little... then a lot! Nothing. I pulled the accel pump off to see if it was damaged... nothing visible.

So up to this point... no adjustments... just drilled and tapped.

Thanks for the link... it's actually the exact procedure that I have been using for the mod. Thanks for the response.


Thanks for the warning about the gasket. Last thing I want in my garage is carb that isn't of any use to me!

As for the running... I'm new to the bike [8 months]... so it might run like crap for all I know.. but it's a HUGE improvement over my CR125! :cry: Actually it has a little bog... but while I was learning to ride it... I was willing to put up with things. Didn't want to tinker too much with my new toy... now.. however... it's time to make things better. Actually I'm looking forward to the improvements that clean carb will bring.


Thanks for the link! It is very informative. I will definately add it to my library of documentation.

Now if the clock would just tick a little faster so I can go home and try to get my bike back to life!

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