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Discussion Starter #1
This wave runner runs fine when it is used every day but when it sits for 7-8 days, it is very hard to start . It just cranks and cranks for what seems like more than a minute (in 10-15 second bursts).

Is it possible that fuel is draining back into the tank? If that is the case, is there some kind of fuel check valve that can be inserted into the fuel line?

Not sure that's is, but it seems like that might be the problem.
 

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Discussion Starter #3
They were rebuilt with genuine Mikuni carb kits about 2 months ago in an attempt to solve this problem. Unfortunately it did not fix it.
 

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Discussion Starter #5
I don't have a compression gauge but I can tell you it runs great once you get it going and if you use it every day or every other day there isn't a problem. It is only after sitting for several days or a week.
 

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Sounds more like fuel pump is draining back to the tank or not pumping as well as it should. A fuel pump has two valves both stop return flow. These come in the fuel pump rebuild kit.
Check your fuel filter for blockage as well, this won't cause your problem but will let you know if there is dirt or water in the fuel tank. The fuel in the carbs does evaporate a bit over time and also changes in air temperature pump some fuel into the intake over time.
You can get a manual primer to put into the line. This will let you fill the carbs before trying to start, just like an outboard.
 

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Discussion Starter #7
I agree, but the fuel pumps are part of the Mikuni carbs and those were rebuilt a couple months ago to try to stop this problem. I paid particular attention to the new pump diaphragms because I suspected they may be leaking. I am going to install a ball bump inline so I can force the gas up out of the tank. That should tell me for certain whether the fuel is draining back into the tank.
 

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Discussion Starter #9
Don't know what a pop off is.
Low speed settings appear to be good when it is running. It idles is very smoothly and it is very responsive to acceleration demands.
Some of the fuel supply lines are original and that just might be the problem. I will replace everything from the tank to the carbs and see if that helps. Thanks.
 

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Pop off is the amount of pressure needed to unseat the needle. It is checked with a pop off gauge. When you did a carb rebuild, did you replace the needle and spring or reuse the old ? For someone that is new to these carbs, I always recommend reusing the old needle, and unless the spring is damaged, always reuse it. How quickly does it start when you hit the starter button ? Should be almost instantaneous. How old is the fuel filter ? Check the plugs and make sure it is burning good (should be a med to dark tan), and might do a compression check just so you know what condition the top end is in.
Most ski's I have had were good starting up to about 4 or 5 days, after that, had to be coaxed a bit.
 

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Discussion Starter #11
I saw somewhere online that it is best to reuse the old needle and spring because using the new one might change the fuel pressure. So I used the old ones.
 
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