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Discussion Starter #1
New here, figured this would be as good a spot as any to post. Just got the creme de la crème of Craigslist specials, a 750 with no papers that the PO couldn't get to run right for a measley $250. Up to ~¼ throttle the bike runs beautifully, idles smoothly, and throttle is snappy and responsive. However, if I hold the throttle between ¼ and ¾, it splutters and bogs and sometimes just stalls out completely. If I hold it wide open, it'll splutter its way past the dead spot and hit redline. Riding it is like the worst case of turbo lag to ever exist. I have tried adjusting the pilot screws, cleaning the carbs (including the emulsion tubes, which helped ever so slightly), checked float needles (not hard or worn), and putting the needles in every single position. I don't know what's been done in the carbs but it's evident that I'm not the first one in there, the outside of the emulsion tubes are slightly marred and I highly doubt the needles are stock. I've looked at what feels like every single forum and every single site to no avail. TIA, and if this post is in the wrong section or if there's a better place for it just lmk.
 

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You are indeed in the correct section and congrats on the find. Air, fuel, and spark are your three options. A teardown and rebuild kit with all matching parts may solve it but it sounds like you have pretty much gone through them already. I apologize, I am new to carbs but are the slides opening correctly? I am wondering if they are opening late and choking it in mid range.
 

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From your description of your symptoms, I would check the slides to be sure they are in good condition. Check the diaphragms, and be sure that both holes are clear. I am wondering if a previous owner may have drilled the holes in the slides for faster lift. If they look bigger than they should be, you could try to block one off on each slide, and see if your condition gets better. The second thing I would be looking at are the emulsion tubes. They get worn and the needles will not seat properly. Commonly causing idle issues, but I have seen a couple cases like yours. Keep us posted...
 

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I just throw this out there, but I had an GL1000 years ago with a similar bogging issue. One carb had a hole in the diaphragm and the slides were a bit dirty and sticky. A new diaphragm and cleaning fixed it.
 

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Emulsion tubes aren't ovalled, but the needles have some pretty evident wear, so I'll go over that again today. Diaphragms look good, slides operate smoothly, doesn't *look* like the holes were drilled out but I'll play around with that too.
 

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One other thing. A friend had a mid range running issue on a 1st gen SV650 (carbureted). He finally found that a spring on the diaphragm was missing.

Otherwise, you might check against the parts list and service manual to make sure everything that should be there, is.
 

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Emulsion tubes aren't ovalled, but the needles have some pretty evident wear, so I'll go over that again today. Diaphragms look good, slides operate smoothly, doesn't *look* like the holes were drilled out but I'll play around with that too.
+1
 

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So after some googling, I've discovered that *none* of the carbs you see when you look up "86 gsxr750 carbs" look like mine. Can anyone confirm? If so, what are they from? They're still Mikunis, but the inlet side and float bowl look different. Wouldn't wanna start ordering parts for the wrong carbs
 

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It's hard for me to tell much at all from that picture. You might have more luck with more and better quality pictures.

There have to be some numbers on the carbs somewhere.
 

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Difficult to tell from that picture, but they at least look like the correct STYLE of carbs. Nicknamed "Slingshot carbs", I believe they are technically RS series carbs. For the most part they are the same up until (I think) 1987. They went semi electronic then. As John suggested, there should be numbers on them you can run to get the exact model.

Where are you located? There may be somebody near (enough) willing to give you a hand getting them sorted out. I must say it, these are the most sensitive carburetors I have EVER dealt with. They are very picky, and difficult to fine tune.

On a side note: what kind of overall shape is this bike in? We like pictures here. We are especially fond of bike pictures, lol...
 

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whats the condition of air box/air cleaner? For it to idle nice and not get full throttle means it’s not getting enough gas.
Check the main jets as well. What was the condition of the needle valves/ float height?
 
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