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Discussion Starter · #1 ·
Hey all

Got some rebuild kits through for the SL350 K0 and set about putting them on. Unfortunately, neither they, nor a different set of coils helped bring the bike to life - lots of coughing and pre-ignition type popping, but no joy. Anyways, in trying to diagnose the problem, I found there was a load of fuel in one of the cylinder bores and none in the other. The subsequent carb strip revealed a couple of things - first, the choke synch lever doesn't (it's fitted at the wrong angle, leaving one gate closed and the other partially open); and second, there's something funny about at least one of the diaphragms.

Here's a photo of the diaphragm/slide from the bottom. As you can see, there are two holes; I'm not sure what they're purpose is (they're not mentioned in the manuals), and this is where I'm hoping you folks can dive in and enlighten me. You'll also notice one of the causes of my problems so far - there's a tear towards the top left corner.



So, from the inside, the diaphragm/slide looks like this:



The plastic plate in the bottom of the diaphragm/slide has four holes in it - all the same size. It's kinda hard to see but I've lined up two of those holes with the two in the top photo (you can see my finger through one of them). Trouble is, I can't find any sort of explanation as to what those holes are for - or whether they should be lined up, or covered up. I doubt they would be there if they didn't have some specific purpose, but I'm lost as to what that might be. The only thing I can think of is they could help the diaphragm/slide to behave in the same way as if the needles were raised (there's no obvious way to change the needle height), but that doesn't really seem right, either.

So can any of you tech heads give me a clue as to what the holes are for - and whether they should be opened, partially or fully closed?

Thanks in advance. And BTW, I'm looking into getting the tear fixed. I think I may know a guy who can replace the diaphragm . . .
 

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Sensei
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The holes allow the "throat" vacuum to be transferred to the area atop the diaphragm. This vacuum is essentially what lifts the slide.... The hole sizes and placement act as a differential orifice, controlling the speed/smoothness of that transfer.... Larger holes would allow "faster" slide response to throttle changes, but make it more susceptable to minor variances (slide would be more prone to "flutter").....Ideally, they should be aligned with two of the holes in the needle plate.... There is a bit more involved, but that's the basics.....
 

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Discussion Starter · #3 ·
Thanks 66.

Both of mine were lined up, probably more by luck than judgement. I'll keep an eye on that when I get the repaired diaphragm back.
 
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