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Old 10-12-2009, 07:10 PM   #33
The Jerk OP
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Joined: Mar 2006
Location: Brooklyn, NY
Oddometer: 2,658
More Jetting ?'s

OK so besides the snap/crackle/pop on decel I've noted in my previous posts (due to lean mix) I've noticed that sometimes, pretty much always on a long, throttle-completely closed decel (like going down a steep hill or coming off the highway), in addition to the usual crackles and pops I will occasionally also get a big BANG! proper backfire through the exhaust. Like the kind that makes people duck because they think someone's shooting.

My question is this: even if I shim the needle and that really helps with the flat spot/lean surge at steady throttle/low throttle openings, when the throttle is completely closed, my understanding is that at that point, the main jet is not in play and everything is going through the pilot/idle circuit. If that's the case, will shimming the needle do anything to address the popping through the exhaust on closed throttle decel or will I still need to replace the pilot jets with something larger?

And if so, where's a good place to shop for replacement Keihin jets?

EDIT: this reminds me: when I drilled out the pilot screw plugs, I found that one screw was factory set a full turn in compared to the other. I later read on a web site somewhere that this was done because the air path to that carb was a bit more tortured in the W650 -- all the air comes into the airbox from the right side and then does not have a very clear path to the left side of the airbox and into the carb. Perhaps I should be sure to take that into account when setting up the carbs so I don't wind up with too rich an idle mixture on the left cylinder.
2000 Kawasaki W650

The Jerk screwed with this post 10-12-2009 at 08:33 PM
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