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Discussion Starter #21
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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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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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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Discussion Starter #25
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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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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Discussion Starter #27
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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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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Discussion Starter #29
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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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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Discussion Starter #31
I have never replaced gaskets or diaphragms in the carbs. Visual inspections look good but that can be misleading. I am going to order a full rebuild kit for all carbs in the off season and replace. You have talked about pop off frequently. I know what that is but I have no clue how to measure it? I will check the sync in the carbs as I have them home for the winter with the reed valves too. They will all be measured and set correctly. I am still curious why the # 1 plug reads so differently. You mentioned fuel lines and pick up tubes but they are all common to all three carbs? They carbs have fuel rails. I am wondering if my entire problem is related to carb #1?
 

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Pop off is the pressure it takes to unseat the needle. It is controlled by a spring and is critical to starting and low speed. it is checked with a pop off gauge. Mikuni makes a nice one. 0-100 psi is what I recommend. Pop off for the cv carbs I believe is 18psi. Check sbt for a kit. There really wasn't much of a kit offered for the cv carbs, but I think they had a wsm half kit I'll call it. Get the pop off gauge and test that before installing the kit, and I would NOT use the spring or needles in the kits. Just really use them for the gaskets and diaphragms. You can try the needles if you want, but the pop off must stay the same. Also check to make sure the return lines are not plugged. There should be a restrictor in the #3 carb before it goes to the tank, and make sure the return between carbs and the tank is not plugged. Pick ups in the tank have little filters on them. They can get plugged.
 

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Discussion Starter #33
Thanks for the precise directions on the pop off. I will look at SBT for a gauge.

I still don't understand the fuel intake scenario you talk about. I have ONE fuel hose feeding all three carbs and ONE return line. There is a hard fuel rail between all three. I will run a wire through the intake and return rails to check for obstructions. Attached are pics of the carbs. You can see the one fuel line and return line in the front.

I will look for a "half" carb kit with gaskets and diaphragms only. Thanks again.
 

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