Mikuni SBN fuel dribble

Ok, I tracked down a set locally.. I also ordered some 66E-24412-00-00 so I will see if that is the same part or not.

Good news is this definitely works. No dribbles with heavy spring and 1.5, 1.8, and 2.0 NS. I did pick up some dribbling (still less than before and kinda intermittent) when I dropped to a softer spring. But I will lower pop off by using heavy spring and larger NS.

I think I'm lean in the mid-range (under 1/4 throttle bog) now, makes sense because of the extra fuel it was getting. But I couldn't fix it with what I had.

Right now I'm at 135 low jet and 32 psi popoff. I got some bigger Lows coming in the mail now.
Here is the Yamaha PN referenced above. It has a pocket milled around the check valve. I think that actually may help even more..

Will try to do some tuning tomorrow with these new ones instled.


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I found this forum doing a Google search, trying to figure my issue with valve bodies.

I'm rebuilding a set of Mikuni 44 I-Series carburetors that go on Yamaha's 66v motor (1200cc power valve), that powers the GP1200R jetski. The screw that holds on the BN34/107 check valve was corroded, and my screw extractor ripped the head off of the screw, leaving the body of the screw stuck inside the valve body. The Mikuni manual identified the valve body as part number BN44/165, so I ordered a new one online. To my surprise, the new one that showed up at my door had the hole directly over top of the BN34/107 check valve, instead of being offset like the OEM one.

I'm not sure I understand the reasoning behind the offset hole in the valve body? How does that help with dribble? What are the effects using the straight thru hole design (6R7-24412-01-00) versus using my OEM style with the hole offset (66E-24412-00-00)? How critical is it that I stick with the offset design?
glad this popped up.

last year i was having the same issue with my dasa 48s. they would dribble at idle, upped the pop off from like 20 to 30 same issue. going to check mine tonight while i set them up for my new motor and compare my valves to the above ones.

maybe mine are completely different than the above posts, but for the 5 min of work could solve a lot of headaches for me or others if it is the case.
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