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Discussion Starter #1
in my experience and reasoning, a larger jet bore means more air flowing through the circuit pushing more fuel with it = jet leaner. I bought katana 750 36mm slingshot carbs and converted them back to GSXR specs with the choke assembly, emulsion tubes and needles, etc. the closest PAJ I could find are 1.45mm, where the GSXR PAJ is 1.55mm. I am currently running huge pilot jets at #47.5, where stock GSXR carbs I believe run #35. I talked to a guy at Sudco and Mikuni only makes these PAJ in 1.5mm and 1.6mm, not 1.55mm. So could 0.05mm difference in jet size really be that effective on these carbs? should I go 1.5 or 1.6?

the Sudco guy only has experience with the aftermarket flat slide carbs, not so much with factory CV units
 

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to answer my own question and possibly help someone else, the purpose of the PAJ is to "emulsify" the fuel mixture, the larger the jet = more air to break up fuel particles = leaner mixture. just like a smaller PAJ means less air and more fuel.

so, with smaller PAJ combined with huge pilot jets to get the bike to run decent, something is definitely wrong. keep in mind these were originally katana 750 carbs, and upon more reading I found that the starter jets (choke) are different on both bikes, with the GSXR having size 45's and the katana having 37.5's. Could this factor into slow-speed drivability?
 

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I replaced all 4 o-rings that go between the intake manifolds and the cylinder head, set my float heights all to 13.5mm, re-checked every o-ring and seal for potential vacuum leaks, blew compressed air through every jet hole, everything checks out fine. I go to start the bike up and its doing the same thing: high idle and hanging revs. it took 4.5 turns out from the mixture screws to somewhat fix the idle

which all leads me to believe that I might just simply need larger pilot jets. currently running 47.5's, gonna go with 52.5's. Sudco lists these jets from size #30 all the way to #60
 

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after about two years of messing with these slingshot carbs trying to figure out my hanging revs and high idle I FINALLY figured out the problem, it wasn't a vacuum leak or jetting that was at fault. the problem was mechanical. Right where the butterfly valves are towards the front, carb #2 throttle plate had too tight of a fit and was rubbing up against the inside of the venturi. if I opened the throttle then closed it slowly, it would stay open slightly along with carb #1. If I flicked the throttle it would slam all the valves shut, dropping my idle. I unbolted and slid it out, sanded down the areas of contact, reinstalled and my problem was solved

another thing I noticed and fixed: the center balancing screw and springs that balance carb banks 1 & 2 with 3 & 4. the individual spring below the screw was too weak, when I cracked open the throttle slightly carb banks #3 (master carb) and 4 would open first before the spring compressed enough to open 1 & 2. the fix? a simple shim/spacer to preload the spring. all carb banks open at the same time now, the way they're supposed to
 

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Good detective work. I wouldn't have had the patience, I may have dumped those for flat slides after awhile.

After about 9,000 miles and 8 years, I exchanged my stock CV carbs for flat sides on my 1989 1100. I am going to put them back on and expect all sorts of quirky problems. I think I'll just do a bottom up rebuild like you and see what happens...
 

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Discussion Starter #6
Good detective work. I wouldn't have had the patience, I may have dumped those for flat slides after awhile.

After about 9,000 miles and 8 years, I exchanged my stock CV carbs for flat sides on my 1989 1100. I am going to put them back on and expect all sorts of quirky problems. I think I'll just do a bottom up rebuild like you and see what happens...
I was very convinced to do that, but my bank account suggested I stick with what I've got and try to work out the problem. the nice thing about these slingshot carbs is that they're very simple and can be taken apart pretty quickly, Ive worked on mine so many times that I can say that
 

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Good detective work. I wouldn't have had the patience, I may have dumped those for flat slides after awhile.

After about 9,000 miles and 8 years, I exchanged my stock CV carbs for flat sides on my 1989 1100. I am going to put them back on and expect all sorts of quirky problems. I think I'll just do a bottom up rebuild like you and see what happens...

Sorry to hijack...

Youre going back to the CVs from the flatslides? if so, whats the reasoning? :cheers
 

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Discussion Starter #8
Sorry to hijack...

Youre going back to the CVs from the flatslides? if so, whats the reasoning? :cheers
I could answer this, the probable reason would be more linearity. CV's are more user-friendly and deliver smoother power delivery if set up properly, also a lighter throttle pull. flat slides are a heavier throttle pull and can be abrupt if you're not careful with your right wrist, not really good for street use or if you're in a corner on a slick surface
 

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how many turns is your Fuel screw out. Standard manual off the top of my head states 1.5 turns but seen various videos on YouTube saying correct jet size is attained when fuel screw sits somewhere between 2 and 3 turns. I'm struggling to get idle setting right with 1/4 throttle bike flies after quarter throttle. Such a pain to adjust fuel screws. How do folk adjust them in situ? Thanks.
 

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how many turns is your Fuel screw out. Standard manual off the top of my head states 1.5 turns but seen various videos on YouTube saying correct jet size is attained when fuel screw sits somewhere between 2 and 3 turns. I'm struggling to get idle setting right with 1/4 throttle bike flies after quarter throttle. Such a pain to adjust fuel screws. How do folk adjust them in situ? Thanks.
my issue had nothing to do with mixture screws :facepalm and you use a small flat head screwdriver or bit to adjust them, how else would you? look at the understanding carbs sticky, do some research and trail-and-error testing, and start your own thread with your problems and they will get answers
 
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Gixxerider86
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