1998 ZXI 1100 Carb Adjustment - Page 3 - PWC Forum: The best hang-out for Personal WaterCraft enthusiasts
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post #21 of 34 (permalink) Old 08-15-2019, 11:34 PM Thread Starter
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Found the oil leak in the ultra 150. It was a hairline crack in the main line from the oil tank right at the oil pump. Fixed that then changed all the oil lines. Then I found a water leak at the bottom of the big bell housing gasket of the jet. The big rubber hose to the housing doesn’t leak. Going to take it apart and check that out. Ski runs really good considering small water leak inside on jet.

Now about the zxi1100. Replaced rubber air intakes and took it out. It Still has the hesitation and loading up at low end. I can’t tell if it’s a lean stumble or rich bog? I guess I need to try lower end 45 jets from 50 and try leaner? I don’t have any higher than 50. Remember the stock ones were 35’s.

Also would you recommend the temp sensor bypass mod?

Anyway going to fix water leak on 150 and scratch my head on zxi1100. Any other ideas on 1100 low end problem? Once it clears the low end top end is great. Thanks.
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post #22 of 34 (permalink) Old 08-16-2019, 06:23 AM
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Try jetting it down. Usually applying the choke a small amount will help tell if it's a lean or rich issue. Are you talking about the water or air temp sensor ?
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post #23 of 34 (permalink) Old 08-16-2019, 12:40 PM Thread Starter
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Would you try 45 or 35 first? It is the air temp short out mod. I understand it advances the timing?
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post #24 of 34 (permalink) Old 08-16-2019, 07:10 PM
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I would try the 35's and see what happens. If it clears up, try the 45's.
Yes the mod for the air temp advances the timing, but just at lower rpms. Helps with hole shot some, but that's about it from what I've heard. If memory serves me, timing is all in around 3 or 4000 rpm anyway. The way the sensor works is to advance the timing at low rpm when the air temp in the hull gets to hot.
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post #25 of 34 (permalink) Old 09-03-2019, 09:05 AM Thread Starter
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I put the 35’s in with new plugs in the ZXI 1100 and thing got much worse. Put 50’s back in and hole-shot improved a lot but still has intermittent stumble. Idle screws are all set at 1 1/2 turns out. Idles good and starts up good. When I choke a little when it stumbles it pulls out of it. Going to pull reeds this winter as top end runs at 7000 but has a slight variation. Might go back from 165 from 160’s on top end? Do you have any other ideas? I guess 55’s would out of the question? Compression is 95-100 on all 3.

The Ultra has a cracked bell/stinger housing on bottom of exhaust chamber. Searching EBay for a good used on that.
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post #26 of 34 (permalink) Old 09-04-2019, 06:23 AM
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Compression should be around 120. If top end is good, and plugs are not fouling, leave the 165 mains. The only reason 55's would be out of the question is if they make it run rich. Best jetting is go big until it runs rich, then drop it until it just cleans up. Surging is usually a fuel starvation issue.
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post #27 of 34 (permalink) Old 09-04-2019, 10:08 AM Thread Starter
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Any idea what the part number is or where I can find a 55 slow jet for the 98 ZXi1100? I have scoured the internet and come up empty.

I forgot to hold the throttle wide open when testing compression. Would that give a lower reading?

I will change the high jet back to 165 as you recommended and change the old fuel filter.

Thanks!!
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post #28 of 34 (permalink) Old 09-05-2019, 06:34 AM
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50 was the largest I saw. If it's intermittent, than I would suspect something else going on also. Could be fuel pump related, and that would explain the high speed surging.
Without me going back through the thread, have you checked pop off ?
Yes, that can make the compression test low.
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post #29 of 34 (permalink) Old 09-23-2019, 10:56 AM Thread Starter
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Finally got around to riding and wrenching on skis. Water temp at Bull Shoals Lake is an amazing 84 degrees in the late September! Never ending summer.

I bought an entire used expansion chamber for the Ultra 150 and everything works perfect now!

On to my problem child 98 ZXI 1100. I took the ski out and the intermittent stumble out of the hole continues. Using 50 slow jets and 160 mains. Pulling on choke quickly fixes stumble every time. I measured compression again with WOT and cylinders warm. 100, 100 and 105. Reading the new plugs was a telling tale. (see pic) The #1 plug (front of ski) was very dark and carboned. #2 and 3 were clean and identical. From these pictures would you think I have a carb problem with #1? I then took the carbs and reeds out. The reeds look very good and tolerance is good. (see pic) I am going to completely tear down carb 1 and look for issues. Also pondering a complete carb rebuild kit. Any words of wisdom? THANK YOU for all your help along the way!!
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post #30 of 34 (permalink) Old 10-07-2019, 04:53 AM
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What was the pop off on the carbs ? Might look and making sure they are still synced. This can be done with some .001 appx 1/4 wide shim stock or any thin, narrow feeler gauge to check the distance between the butterflies and venturies, or use the instructions in the manual with a depth gauge. Can get a cheep one at harbor freight. Pilot/low speed screws should be at 1 3/4 out. Main jets should be 165's for altitudes up to 6600ft. If you noticed a power loss in mid to upper throttle with the 165, then leave the 160's, but if now power loss was evident, use the 165's. You don't want to go lean.
Check and make sure the pick tubes in the tank are clear, all fuel lines are in good shape and tight (might be getting a slight air leak), might just go ahead and replace them. Using the manual, make sure all the needle arms are at the right height and are at the same height. Make sure the pulse line is good and not leaking. Might put new zip ties on it to be safe. Make sure the inlet filters in the carbs are clean. When was the last time you put new gaskets and regulator diaphragms in the carbs ? Again, it still might be the fuel pump, but need to eliminate everything else first.
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