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Discussion Starter #1
Hi guys, I bought a Kawasaki 650sx last week and got it running. I rebuilt the carburetor, replaced all fuel lines and filter, and replaced the check valve on the tank vent because it was stuck open. I believe the carburetor is a mikuni 44mm or maybe a 46mm. It has a 110 low jet and 140 high. The settings were initially set at for the high speed at like 2.5 out and low speed like 2 turns. I kinda forgot but that is about what they were at. Before the rebuild at those carb settings it would start up very well. Only a couple cranks cold. But it would bog when revved up. So that is why I did all that work. I heard that those original carb settings were way too rich so I am 2 turns out on high and 1 ½ on low speed. Now it is very hard to start without starting fluid and when I get it running I have to keep on the throttle and it still bogs. What do you guys think? Thanks, John.
 

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Carb should be a 44. That's the common carb to use.
Did you check pop off ? 2 turns out on most mixtures screw is high and needs rejetting or pop off adjusted. How is full throttle ? That is what the high speed screw affects. Inaccurate pop off can contribute to a lean or rich condition on start up, at idle, and off idle acceleration. Ideally the butterflies should be open appx .030-.040 at idle.
What aftermarket parts does the ski have ? what compression ?
Both screws at 1 turn out should be a good starting point.
decent starting point for jetting a stock setup would be 100-105 pilot, 130-145 main, 2.0 n/s at 20psi pop off (black spring).

Low speed screw handles starting and idle quality, pop off starting, off idle acceleration and some of first 1/4 throttle. Low speed jet up to 1/4 throttle. High speed jet up to 3/4 throttle. High speed screw 3/4 to full throttle. Do not use the mixture screws to adjust idle speed. The best low speed mixture setting is highest smooth idle. If idle rpm goes to high, use the idle screw to drop it, and readjust the mixture screws until a smooth idle at designated rpm is achieved. Shut it off, wait 10 min, and start it back up. Should fire off almost instantly, hot or cold.
Pop off also affects starting and idle. Pop off can be somewhat compensated for with changes in low speed jets, ie low pop off would take a smaller jet to lean it out.
 

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Discussion Starter #3
I don’t know pop off pressure or compression. Compression sounds pretty good but I haven’t checked. In the rebuild kit I got 2 springs. I just reused my old one. I will try to tune it at 1 turn out. It seems like it is running rich to me and flooding out. Are my jets fine or do I need to get different ones? When I first got the ski it was at like 2 turns out on both screws. It started and idled good then. Why would that be?
 

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Discussion Starter #4 (Edited)
UPDATE:


I just ran it on the hose and ended up turning out both screws 2 turns. I messed with it a little and I am about 1 ½ on low and 1 ½ on high. When I rev it past half throttle it revs down and makes like an “BAwwww” sound and when I rev it all the way at full throttle it cuts in and out. Is that lean or rich? And high speed or low speed? Thanks again
 

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Discussion Starter #7
I turned out both screws 1.5 turns and it seems to run better. I was talking to some other people and they said that it might be a spark issue because of the cutting in and out. It almost backfires so that makes sense. What do you think?
 

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High rpm surging that bad could be a lean issue. Need to know what the compression is (this is just to verify that it is good, and they are the same) and verify pop off. Any more than 1.5 out, or any less than 3/4 out on the low speed screw requires pop off adjustment, and if on the high speed screw it requires rejetting. A high pop off will make a lean starting and idle issue, and a low pop off will make a rich issue. Best setting for low speed screw is max smooth idle idle speed, then just a tad more out (less than 1/16 turn), but should still be smooth. Test it by shutting it off, waiting 10 min, then fire it up with out touching the throttle. Should start instantly.
Have you pulled the plugs to see what they look like ?
 
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