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  1. #1
    jstanfi1's Avatar
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    2000 Yamaha XL 800 looking for some advice

    This seems like the most honest group of folks on the web...I'm expecting some brutal honesty here! I'll caveat and say that this is the family waverunner and we will frequently have inexperienced riders using it, so I'm not looking to put much cash into it beyond what it takes to keep it working right.

    I've got a 2000 Yamaha XL 800 with about 200 hours on it. I rebuilt the top end but did not have the cylinders replated or sleeved, and after the rebuild have compression of 120 in the front and 115 in the back. In addition, I had the carbs rebuilt, installed, and set by the dealer. I also replaced the power valve servo motor and cleaned the valves and installed the waveeater clips while I had the engine apart. Replaced plugs, etc. Dealer inspected the exhaust from the manifold all the way back and found no obstructions. Runs great and takes off reasonably well, minimal cavitation for a waverunner this big and relatively underpowered for its weight.

    My question is...the ski is revving up close to 7000 no problem, but my top speed is about 40 mph, whereas I gather this ski should break 50 pretty easily. The only odd thing I notice is that as I hold the throttle, it seems that the waverunner doesn't respond any different from 3/4 throttle to full throttle. I would think this means that the throttle cable is adjusted too tight, but I'd appreciate some thoughts as to how to check if the throttle is in fact opening all the way.

    Attached are pics of my jet pump and impeller. The impeller has a few dings but very little on the trailing edges, and the clearance looks very tight. I can get little more than a business card between the impeller and the wear ring. I wouldn't think the pics attached suggest the unit should be running 10 mph slow on the top end.

    So I guess what I'm asking...if everything is working properly, what kind of top speed should this unit produce with 250# of weight and the compression numbers above? Maybe everything is fine? If not, does the jet pump look ok? I inherited a R&D Intake Grate with the purchase that I haven't installed as from what I've read it seems like that benefit is mostly produced when matched with a different pitched impeller. Should I install it without a new impeller? If I do, is it installing a pump shoe filler kit if I'm not doing any other mods?

    Thanks in advance...I know you guys want to talk performance, but in my other hobbies I've found the performance oriented guys also are in the best position to say what works and what doesn't.
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  2. #2
    surferd15's Avatar
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    My buddy had one, 2001, but same ski, he put in a Solas impeller that made a huge difference, his speed was 53-54 GPS, rider weight around 180lbs. I would think you should be able to hit 50+. When you did the work on the motor did you replace the oil lines and check flow? His blew up 3 times..1st from water getting in the gas tank from a small crack in the seal, 2nd-not too sure on cause but think it was the oil line or not letting the pistons heat up-Wiesco--(never replaced oil lines but rebuilt again) and 3rd time blew lack of oil. They fixed it one more time and traded it in! Impeller looks a little banged up from the rear like something went through it, not sure how the leading edges are get up under it and take some pics from the front area. Tolerances look tight.

  3. #3
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by jstanfi1 View Post
    Attached are pics of my jet pump and impeller. The impeller has a few dings but very little on the trailing edges, and the clearance looks very tight. I can get little more than a business card between the impeller and the wear ring. I wouldn't think the pics attached suggest the unit should be running 10 mph slow on the top end.
    If your impeller/wear ring clearance is more then one business card then its out of ideal spec. Of course using a feeler gauge is far more accurate.

  4. #4
    jstanfi1's Avatar
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    Quote Originally Posted by surferd15 View Post
    My buddy had one, 2001, but same ski, he put in a Solas impeller that made a huge difference, his speed was 53-54 GPS, rider weight around 180lbs. I would think you should be able to hit 50+. When you did the work on the motor did you replace the oil lines and check flow? His blew up 3 times..1st from water getting in the gas tank from a small crack in the seal, 2nd-not too sure on cause but think it was the oil line or not letting the pistons heat up-Wiesco--(never replaced oil lines but rebuilt again) and 3rd time blew lack of oil. They fixed it one more time and traded it in! Impeller looks a little banged up from the rear like something went through it, not sure how the leading edges are get up under it and take some pics from the front area. Tolerances look tight.
    The oil lines were recently replaced. Too many horror stories like your buddy's out there!

    I think I'll go ahead and pull the intake this week and take some pics from the other side as you suggest. But assuming the leading edges are ok, would a dinged up impeller cost 10 mph, or is this just a 120 psi motor giving all it can?

  5. #5
    jstanfi1's Avatar
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    Quote Originally Posted by Cutlass View Post
    If your impeller/wear ring clearance is more then one business card then its out of ideal spec. Of course using a feeler gauge is far more accurate.
    I got a feeler gauge on it today and the biggest gap is .02. That won't cost 10 mph will it?

  6. #6
    Myself's Avatar
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    Feel both cylinders after a ride. Maybe you're losing spark in 1 cylinder?

  7. #7
    RipNSki's Avatar
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    It won't do much over 50 stock... I had one and it did high 40's... The 1200 does about 50+

    Ripper

  8. #8
    jstanfi1's Avatar
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    Quote Originally Posted by Myself View Post
    Feel both cylinders after a ride. Maybe you're losing spark in 1 cylinder?
    Actually had one cylinder not firing on this thing in the past and it would get up past 3000 rpm so I think I'm good there. Thanks though!

  9. #9
    jstanfi1's Avatar
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    Quote Originally Posted by RipNSki View Post
    It won't do much over 50 stock... I had one and it did high 40's... The 1200 does about 50+

    Ripper
    Thanks, that's kind of what I thought. Since I can barely hit 40 I'm trying to figure out if that's to be expected with my engine at 120 or if there's another culprit. Frankly I can live with it as-is if its just a motor issue.

  10. #10
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by jstanfi1 View Post
    I got a feeler gauge on it today and the biggest gap is .02. That won't cost 10 mph will it?
    The spec is generally .010 to .014 inches. There is also a max clearance limit of .024inches listed in the service manual. So I think your impeller clearance is definitely costing you some cavitation off idle and a loss of some top speed, but probably not all of that 10mph.
    Look under the ski for things that could cause drag as it glides through the water. Is the pump shoe/intake grate hanging down low or the ride plate shimmed or hanging down? or maybe you need a pump plug kit. just throwing some thoughts out there

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