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  1. #1
    sjorge3442's Avatar
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    Wave Raider 760 Quit Running. Suspected Fuel Problem

    Whats going on everyone. I grabbed a 760 wave raider a few weekends ago that was in pieces. I put the whole engine back together and she fired right up. After having issues with the starter switch (it was getting water in it, causing it to short, I pulled the switch apart and it fired back up. nothing like being left in the water 2 miles in the open bay with no power. I plan to elimate that switch and to only make a tether and power button switch out of dirt bike parts

    Any way, my friend jumped on it to ride 2 hours after being docked and it was bogging real bad. He was riding up to me in open water and it stalled out on him, and it wouldnt start. We towed it home again and tested for spark and it was getting it. We gave her a quick shot of ether and it started, pointing up to a fuel problem. Now it will only run with ether.

    I pulled the carb (yeah, I have one of those 2 to 1 carb conversions) and gutted it, but found nothing wrong. Put it back together and i still had no luck. She just cranks and cranks and cranks.

    I plan to pull the fuel filter tonight and run a direct line to see if thats the problem, but I feel like its not. What would cause this? I should mention I had a slight stutter from idle that I could not eliminate adjusting the pilot screw.


  2. #2

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    Why eliminate the switch? New ones are fairly inexpensive, I just installed one today. As for the engine....did you use new seals? Gaskets? Properly seal the cases? Pressure test the engine upon reassembly? Find out WHY it was in pieces? I am not dogging you out....but I had a feeling that motor wouldn't last long. Never trust that someone else measured everything correctly. First of all....NEVER USE ETHER ON A 2 STROKE! It cannot be overemphasized! Now.....start by a compression test. Report back. Got a feeling your motor is trashed.

  3. #3
    sjorge3442's Avatar
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    The entire engine was installed with new gasket. Compression is a Solid 130 on the front and 125 on the rear cylinder. Those numbers haven't changed since the engine quit running. I did a leak down test this afternoon and she held pressure fine. This is 100% a fuel issue.

    In regards to the ether. I'm not crazy about it, but a quick little shot isn't going to kill the engine. Plus it gives a little hope into eliminating other issues.

    I talked to the other owner and he said he tore the engine down just got replace the leaky base gasket.

  4. #4

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    What type of compression gage are you using? Those numbers if accurate are very low. The rear cylinder should be slightly lower than the front.....A few psi. Yamaha manufactured the 760 that way. If those numbers are accurate, 125 is too low to let it run.

  5. #5
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    Quote Originally Posted by butterbean_29512 View Post
    What type of compression gage are you using? Those numbers if accurate are very low. The rear cylinder should be slightly lower than the front.....A few psi. Yamaha manufactured the 760 that way. If those numbers are accurate, 125 is too low to let it run.
    130 on the front and 125 on the rear cylinder, that is a slightly lower number. These are the same numbers that I got when I tested the engine after the first start up. The engine pulled great, it was keeping up with all of the other skis we had out there until it decided to not work.

    I've been reading up on the SBN carb so I will be playing with that quite a bit tonight. Im goign to thrown new plugs in, start with a fresh baseline on the carb and dismantle the handling bar switch again. I think there is something seriously wrong in the switch. You know how much is sucks to get stranded just because the switch wont work? Thats why I want to remove it. It is happened once, its bound to happen again. its not water tight. There is no gasket around it, which makes no sense to me.

  6. #6

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    Each individual switch in the box is waterproof. They do wear out, best option is to replace it. Honda East Toledo has the switch for 128.99, free shipping. They are an eBay store. As for those compression numbers.....The engine is way down on compression. Are you doing it properly? Throttle must be held wide open during test. Check one cylinder at a time. Leave the other plug in. If those are good numbers
    ...you are gonna have to pull the engine and resolve the compression. Normal compression is 150-160 front, 150-155 rear....give or take a couple of psi. Also, read OsideBill's sticky on how to properly build an engine. Its For A Triple Cylinder, but it is the same for the twins. Follow it and you will build a good strong motor.

  7. #7
    sjorge3442's Avatar
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    Quote Originally Posted by butterbean_29512 View Post
    Each individual switch in the box is waterproof. They do wear out, best option is to replace it. Honda East Toledo has the switch for 128.99, free shipping. They are an eBay store. As for those compression numbers.....The engine is way down on compression. Are you doing it properly? Throttle must be held wide open during test. Check one cylinder at a time. Leave the other plug in. If those are good numbers
    ...you are gonna have to pull the engine and resolve the compression. Normal compression is 150-160 front, 150-155 rear....give or take a couple of psi. Also, read OsideBill's sticky on how to properly build an engine. Its For A Triple Cylinder, but it is the same for the twins. Follow it and you will build a good strong motor.
    Gotta remember, I rebuilt the engine with old rings and pistons. These numbers are COLD compression numbers. They will bounce up a bit with a hot engine, which I cant do, since I cant run the engine. I've been building 2 stroke atv race engines for over a decade. I am fully aware of how they work, how to build them, and whats makes them fail. My ATV engines have won numerous state races and championships. used rings are ok. The difference between 150 PSi (Which is a hot engine number) and 125, is not the worst thing in the world. Sure, it could be better, but for reusing old parts its actually really good and again, they are runable numbers. There is no reason why the engine wouldnt run with these numbers. Hell, it ran on the open water at 50 mph with these numbers before it quit running.

    I dont mean to sound like a dick, and I know you've helped me a lot already, but I know my problem is not with the pistons, head or rings. my compression recordings havent changed between the time when the engine was running and when it stopped. Those numbers are consistent. Also, im sure my numbers are incorrect either way as I broke my snap on gauge last week and have been using an autozone gauge since then.

    $128 for a new switch that could easily be eliminated for $35 is ridiculous. I'll just rewire all of those buttons. There is no need to dump that much money into a switch on a 20 year old ski. It makes no sense. Im not looking to restore this thing, just get it running so I can have some fun with it to determine if I would like to buy a newer/nicer ski.

    I'll be pulling the carb again tonight to see if there is anything that I overlooked during my weekend tear down, while on the beach. We'll see.

  8. #8

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    the thing about the switch is it is built for marine duty in a hostile environment. Something else may work, but not for long. And they never break down and quit working while on the trailer. Also, a ski/boat is unlike anything else. They are built to run at WOT for extended periods of time, Dirt bike engines are similar in the way they run, but thats it. A dirt bike engine is not run at WOT for extended periods of time. You just don't get on a bike, rip open the throttle, and run until the tank is dry. It would never last under those conditions. But those are exactly the conditions a ski operates under....often times even worse than that...wave jumping, etc.
    All the advice that has been given is from people who have worked through problems exactly like you are having, and want to help others fix the problems with their skis...and help them get back out on the water for the least amount of money and headache.
    Did you check the ring gap and piston to cylinder clearance when you reassembled it? Can't remember off the top of my head the piston clearance, but the ring gap is .012 +/-.004 I would get a good, reliable compression gauge, and verify those numbers again. I personally use an Innova from OReillys. Has the stainless hose. Very reliable and rugged. Compression should be checked cold. If those numbers hold out when using a good gauge, they are low, and must be corrected. I built my 760 with the wrong size rings, and spun it before I installed it back in the ski. 155 front, 151 rear. Perfect compression....lasted through 2 tanks of gas, ran perfect, then BOOM! A very good learning experience! Don't get caught up in how it ran when you first put it back together. As an FYI, if you do modify the switch, the tether is a requirement, and must remain in working condition. And the 150 psi is a cold compression number. No one cares about the hot numbers. We always check the hot numbers for information only.
    Last edited by butterbean_29512; 08-06-2014 at 03:16 AM. Reason: add technical information

  9. #9
    sjorge3442's Avatar
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    Thanks for sticking with my butterbean.

    When i rebuilt the engine, it was all old pistons and rings. I used NEW gaskets everywhere. The ring gap was .013 (Couldnt be any more perfect) , threw everything together and it fired first try. Ran through about 8 gallons of gas and she pulled awesome. Then that was it. She was barely idling, then it would hesitate, then rip real good if you could keep it running and thats when I trailer-ed it. Compression from rebuild to where I am now, with the same gauge, is still the 125 and 120 i mentioned.

    After tinkering around last night (I pulled the carb apart and checked everything, but I am pretty sure the PO had just rebuilt the carb) everything was spotless and looked great. I started playing around with tryign to get it started when I think I made a realization. I think my spark is so weak that its getting blown out before it even has the chance to ignite the fuel. I gotta borrow a friends multi-meter tonight since I only have a cheapo harbor freight one, but I am going to run some tests on the electrical system. If everything checks out in this department, then the ski will be getting a new top end. In my past experience, weak stators would come out of no where and cause issues just like this.

    Does this sound like a good plan to follow?

  10. #10

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    I always thought the spark looks weak on both of my skis. I'd use a spark tester, one that has an adjustable gap. I don't know if they specify a specific distance the spark should jump but .024 isn't a big distance. Also, your reeds could cause that low compression. I'd check those before pulling the top end. Stock fiberglass ones can crack.

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