Carb jetting issues SXI Pro? Carb size?

[johnmx854]

I currently have a 1998 Kawasaki 750sxi pro that I bought used and really hasn't been running correct since I got it.. So here what the skis has for aftermarket parts and what I've come across since trying to tune it.. 750 big pin motor to start, factory wet pipe, V-force 3 reeds and what at the time I thought was a mikuni 46mm sbn... Did some research and got the getting correct so I thought and still ran like crap.. Took the flywheel off the find out it had a vilder flywheel with a different timing and a stock ignition which didn't work.. Put a stock flywheel on which made it rin much better which brought me back to carb issues.. Like I said before I thought it was a 46 untill on a whim I measured it and measures 48mm... I can't seem to find one online like it and would imagine it changes the jettin info.. Right now I have a 155 main and a 122.5 low speed and runs ok but not to the potential that I believe it has.. Below are pics of the carb disassembled and hopefully someone has tuned a carb like this before.

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[Magyar68]

I guess start with being more descriptive with the way it behaves. If it is out of the Water, Does it idle on its own? What happens when you go from idle to WFO does it stumble then Take off, or does it just Die? If you haven't already, use the Mikuni Tuning manual to help get the jetting sorted out. Find a friend with alot of jets to try. http://www.mikuni.com/pdf/sbn_manual.pdf Good Luck

 

[johnmx854]

Out of the water it runs perfect and crisp with almost perfect throttle response. In the water is a different story.. Mid to top end is great.. Bottom end is my main problem now.. From idle to 1/4 throttle in the water it pretty much falls on it face and does not want to pull out of the water.. I've tried from 117.5 to 127.5 pilot sizes without getting it perfect.. Like in I'm trying to jump a wake and let off the throttle to roll the first wake before hammering down it falls on its face and I almost eat poop but I can hold it wide open and it rips across the water.. Not sure I'm
My air filter is too big and lettin to much air in off the bottom? Not sure been screwing around with this thing for months and haven't got it right


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[Magyar68]

Is this a stock Engine? like no porting, or over bore?

 

[johnmx854]

Stock engine.. Just purchased a stock used one out of a zxi because the motor I had in it was over ported and pretty much ruined by the guy before me.. Has v force3 reeds, factory pipe and this carb which is all that is done with motor modifications... And as well as playing around with the carb I have been playin around with the water screws on the pipe too.. I went to factory's website and set the screws to their settings and the pipe its self wasn't to hot but the bolts that hole the pipe into the manifold were hot to the point where when I dripped water onto it, it sizzles a lot as if those bolts are red hot and I know that can effect the power curve as well..


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[johnmx854]

This is what it sounds like out of the water which I thought sounded pretty good but no the same under a load


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[Magyar68]

Ok your pumping it. needs to idle for like 5 seconds and then you reach up to the throttle Pin it and hold it for a Few seconds.
What Seat size are you using in that carb?

 

[SXIPro]

Dump the AM flame arrestor and put a stocker back on. You're welcome.

 

[Magyar68]

The Stocker will not work on that Carb. And it doesn't sound like he has one.

 

[johnmx854]

I'm not sure what needle and seat size I don't know if it's worn off or what I can't see it anywhere but I'll look again.. I have the stock carbs that come on the zxi750 which are dual keihns...those are on deck if this carb keeps breakin my balls.. Some people have told me that this single 48 is too big and others says its the best for bottom end. At this point I'll try anything.. I'll def take the carb back apart and try to find out what needle and seat are in there.. I put the black spring in for the pop off pressure and that helped a lot as well....


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[Magyar68]

If you try the Duels from the Zxi you should start with 125/75/40 or 45's can work it may have a slight bog in the midrange. depends on the boat.. That carb appears to haven Modified, the top has been ground off and replaced with an aluminum Ring where they mounted the Primer nipple, still has the atomizer in the throat so I do not think it has been bored. You may have 2 problems to large a low jet and to small a High Jet. Do you know what pop-off you have? is there fuel dribbling down the throat during idle?

 

[johnmx854]

I reluctantly say I do not have a pop off pressure gauge but looks like I need to buy one.. Off hand I can't remember if there was any gas dribbling down the throat but I think there was but will double check to make sure.. It does look modified but in my searches I see that blowsion sells what looks like the same carb... Not sure if this is that one or modified to match..


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