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  1. #1

    Yamaha wave raider 700 carb jetting issue

    The first issue is when I accelerate from anywhere below about 1/4 throttle to above 1/4 throttle as soon as i hit about 1/4 throttle the engine almost stalls but once the engine gets over 1/4 throttle it runs fine. It seems like it would run all day either at idle or above that 1/4 throttle area. I want to rebuild the carbs but not sure what to re-jet it too. which brings me to my second issue it has 2 different size main jet on carb has a #120 the other has a #130 pilots is a 67.5 why would someone put different main jets. I'm at about 4000 ft of elevation my engine doesn't have any mods that i can tell but was thinking about doing an oil pump block off


  2. #2
    Welcome to the Forum. You would do well to research the How To and FAQ section of this forum to answer a lot of common questions. No disrespect meant by that comment, but there is a wealth of knowledge that is available if you take the time to read it.

    According to the parts listing for your ski, they are supposed to have different jets depending on the front or rear. 120 and 130 is correct. To diagnose your problem, do the following in order.

    1. Check the compression of both cylinders with one spark plug in and throttle wide open. (If the carbs are off, as it sounds like they are, you can still do the compression test) Should be in the 120-130 range but not that important as long as they are both within 10% of each other and above 100. If good, go to step 2. Low compression on one cylinder will give you a significant bogging at lower speeds.

    2. Make sure you have fresh fuel in the ski. (less than a month old) If there is old fuel, siphon it out and start fresh. Bad fuel will give you a bogging in the low end.
    3. Make sure your fuel lines are pulling fuel from the tank. Leave the gas cap off to test. Try the reserve setting to see if you notice any difference.
    4. 4k is about the limit of not needing to rejet so I doubt if the elevation has much to do with the problem.
    If the above tests are non-conclusive, then take the carbs off and

    5. Rebuild the carbs with genuine mikuni parts and check the popoff pressure to make sure the needle and seat are performing properly. Research this site for numerous discussions on pop off testing and where to get or build a tester.

    To save you some time here is a link to a step by step guide to rebuilding a carb.http://www.greenhulk.net/forums/showthread.php?t=11134

    Many recommend removing your oil pump. In 40 years of operating Yamaha engines of all types, motorcycle, golf cart, 4 wheeler, outboards, pwc I have not had an oil pump failure on my equipment, ever. I have heard of oil pump failures in watercraft that get submerged and the 97ish to 2005ish pwc's had issues with the lines coming loose due to shortness of the lines and crappy wire ties but generally, if you make sure your lines are good and have quality clamps on them, having too much oil (premix) at lower speeds to compensate for high speed operation doesn't strike me as the best way to handle lubrication. Just my 2 cents but others disagree vehemently on this subject and point out that you can guarantee that you will not have an oil related failure by going with premix. Your choice.

    Take your time, get factory parts and read up on the subject and your ski will be back to like new when you are done. Best of luck.

  3. #3
    Quote Originally Posted by cnyman View Post
    Welcome to the Forum. You would do well to research the How To and FAQ section of this forum to answer a lot of common questions. No disrespect meant by that comment, but there is a wealth of knowledge that is available if you take the time to read it.

    According to the parts listing for your ski, they are supposed to have different jets depending on the front or rear. 120 and 130 is correct. To diagnose your problem, do the following in order.

    1. Check the compression of both cylinders with one spark plug in and throttle wide open. (If the carbs are off, as it sounds like they are, you can still do the compression test) Should be in the 120-130 range but not that important as long as they are both within 10% of each other and above 100. If good, go to step 2. Low compression on one cylinder will give you a significant bogging at lower speeds.

    2. Make sure you have fresh fuel in the ski. (less than a month old) If there is old fuel, siphon it out and start fresh. Bad fuel will give you a bogging in the low end.
    3. Make sure your fuel lines are pulling fuel from the tank. Leave the gas cap off to test. Try the reserve setting to see if you notice any difference.
    4. 4k is about the limit of not needing to rejet so I doubt if the elevation has much to do with the problem.
    If the above tests are non-conclusive, then take the carbs off and

    5. Rebuild the carbs with genuine mikuni parts and check the popoff pressure to make sure the needle and seat are performing properly. Research this site for numerous discussions on pop off testing and where to get or build a tester.

    To save you some time here is a link to a step by step guide to rebuilding a carb.http://www.greenhulk.net/forums/showthread.php?t=11134

    Many recommend removing your oil pump. In 40 years of operating Yamaha engines of all types, motorcycle, golf cart, 4 wheeler, outboards, pwc I have not had an oil pump failure on my equipment, ever. I have heard of oil pump failures in watercraft that get submerged and the 97ish to 2005ish pwc's had issues with the lines coming loose due to shortness of the lines and crappy wire ties but generally, if you make sure your lines are good and have quality clamps on them, having too much oil (premix) at lower speeds to compensate for high speed operation doesn't strike me as the best way to handle lubrication. Just my 2 cents but others disagree vehemently on this subject and point out that you can guarantee that you will not have an oil related failure by going with premix. Your choice.

    Take your time, get factory parts and read up on the subject and your ski will be back to like new when you are done. Best of luck.
    thank you for your reply

    what would you suggest for above 4000 feet our lowest lake is 3800 feet but the other lake we like is at 5600 feet. is there a reason for the 2 different jet sizes
    Last edited by mwmiller1983; 02-18-2014 at 02:53 PM.

  4. #4
    The reason for the two jet sizes is that one cylinder tends to run leaner on the 700-760 engines. I guess it is part of the design or the act of accelerating causes something to be out of balance. Again, I really don't think that ~1k feet will make that much difference if the machine was tuned for the lower altitude. Setting the mixture screws so that it runs perfectly at the lower altitude would just mean that you would be slightly richer (air is less dense at altitude so that would mean more fuel compared to the air) at the higher altitude but still safe. Make sure you start with the screws adjusted like it was before you had the problem, then adjust them from there. Be sure to read the massive amount of info available on how to adjust the carbs in the FAQ section. If you find that your plugs are fine at lower altitude but load up at higher ones, tweak the mixture screws in 1/4 of a turn at a time until the issue goes away. You should have enough play to cover the change in level but my experience is that while machines run less strong at altitude, it rarely requires a jetting change.

  5. #5
    a little update i took a look at the other side of the carbs off. i now understand why they are jetted differently one carb has the fuel pump mounted directly to it and the other is feed off of that. after pulling apart the fuel pump i found corrosion build upon the pump side that might of caused low fuel pressure do you think this could cause the issue? I'm going to pressure check the cylinders tomorrow night.

  6. #6
    pressure check was good tested 3 times 130psi both cylinders

  7. #7

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    the reason for the different jet sizes is to compensate for torsional twist of the crank while under load. Group K has a good article that explains it. Think of the crank like a piece of garden hose and try to twist the ends in different directions. The mag side piston stays in time while the pto side piston twists slightly out of time. The richer jet gives the pto side piston a richer mixture, preventing a seizure of the piston. If you change the jets and run the same jet on both carbs, you would seize the pto side piston in just a few minutes of run time.

  8. #8
    Yes! crud inside a carb can cause a flat spot in acceleration. Make sure to check and clean your fuel selector switch. Take it off, run carb cleaner through it and blow it out with compressed air. Thanks butterbean, for the explanation on the lean cylinder. I knew of the symptom but never heard of the cause.

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