X2/650sx stock headpipe differences and modification possibilites - Page 2
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  1. #11
    Top Dog Benflynn's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    And keep in mind that porting a 2 stroke is much more involved than a 4, you almost can't mess up a 4t, but u can ruin the performance and melt one down with a poor port job on a 2t
    Last edited by Benflynn; 02-15-2019 at 01:46 AM.

  2. #12
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    Quote Originally Posted by Witrebel View Post
    I am 100% running dual cooling with separate lines for motor and pipe. Going to enlarge the flow through the manifold gasket and do the Group K mod to the lower passageways as well. I can always choke it down if I have too much flow, but my understanding is keeping that head cool is crucial to avoid detonation in a high power setup. The other advantage I see is being able to tweak cooling flow on the engine without affecting flow rates in the pipe.

    I actually rode a big pin 750 swap in an X2 when I went to buy it, had zero hit and just completely underwhelmed me. I believe it had a coffman pipe too. The more I read the more I realize its ALL in the tune and setup. Granted if I ever get on a properly setup/tuned high displacement motor I am sure it will ruin me. I just feel like I can learn the "tuning" art and get my education cheaper by doing it to a 650 platform where parts are cheap. Once I have it mastered I want to switch to 701 based stuff.

    Yeah I am looking to build on that thread and do a sort of "advanced" pipe mod including dynamic water injection. I will for sure be drilling the stock water box out as well. I have an SBN44 for the carb and a nice intake mani with built in read stuffers. Impellers are a real funny thing to me, no one seems to have a solid explanation for pump dynamics. Seems like this is the meat and potatoes of the equation, I need a good torque/loading curve for various impellers.
    Sounds good about the cooling set up. And yea having the flows independent of each other is really worth it.

    I would venture a guess and say that 750 X2 you rode was set up incorrectly. I'd be interested in hearing the specs on it. With 750 swap skis, it's very easy to do a swap, but harder to set one up that runs well. Especially if that's a big pin cylinder with high port timing and a single carb engine. But even duals if improperly set up will not have good throttle response, especially the oem dual Keihins. If it had a Coffmans pipe the ski was even more poorly set up. If done right, there will be a big difference between a low end / freestyle set up 750 dual carb and a 650. Big, big difference power and torque wise.

    That said, if you're looking for max hit right off the line to about 10mph or so, there might be ways to make a freestyle ported 650 or a yamaha 701 hit harder. But for general rec riding a well set up 750 is not bad.

    In our group of ~25 skis the hardest hitting 750 limited of all is a limited 750sx cylinder / oem dual Keihins / Blaster FP in a X2. We have not tried any Yamaha engines but I am skeptical about a 701 based engine being able to keep up, unless you're talking 0-10mph or a much higher CC engine that uses the 701 bottom end. The port timing will help the Yamaha but the 750 and 800 engines will make more power and torque across the power band.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1995 SJ MINT:
    [TBD]



  3. #13
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    One more thing about the carb to consider. The only reason to choose a single is if you want better fuel range, or want simplified tuning. Duals will produce more power and torque across the entire power band. It's roughly a 10hp jump depending on your set up. Granted this isn't a straight forward on a 650 engine with manifolds being rarer but something to consider.

    One more thing, I'm definitely not a Kawasaki fan boy. My primary riding ski is a stock 2009 SJ and I'm building a 2009 with a Kawasaki 1100 now. My stock SJ has vastly more low end than the factory piped 750s in our group. As in, one time when I went from my ski to my friend's pro with a factory pipe, as I pulled myself out of the water I almost went over the bars on the pro, because I was anticipating the same low end from my SJ which never came. Yamahas do have way more hit 0-10mph even stock. But a big part of that is the 144 pump. Yamaha engines have their place, but a lot of time the big reason guys want to swap is because they're feeling the torque of the yamaha engine matched to the bigger pumps. Yamaha engines have a very flat power band when in a Kawi ski with a smaller pump.

    I have yet to see a good comparison between two similarly set up skis, one with a 701 and one with a 750. Both dual carb, both 140 pumps. A X2 would be a good platform for that comparison. But most people if they're going thru that trouble, will put a much bigger cc yamaha based engine in their ski.
    Last edited by theVetteman3; 02-15-2019 at 08:21 AM.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1995 SJ MINT:
    [TBD]



  4. #14
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    Quote Originally Posted by Benflynn View Post
    And keep in mind that porting a 2 stroke is much more involved than a 4, you almost can't mess up a 4t, but u can ruin the performance and melt one down with a poor port job on a 2t
    Yea absolutely, don't go beyond your capabilities or you'll destroy your engine.

    That said, port matching and polishing the exhaust ports is pretty straight forward. The key is to not change the size or any dimensions. Changing the size of ports is where you get into trouble. Also I need to clarify about that Yamaha 650 I ported. That cylinder is hugely conservative with very small sleeve port windows, and the sleeves have about a 1/4" step that hangs down from the top of the cylinder's exhaust port. Removing that material and polishing everything is how I got my 4mph gains. I would not expect a 650 Kawasaki to yield as much of a gain for just that work.

    Back to the OP, let us know how things go on this. Having a tach and a waterproof GPS are good ways of tracking the performance impacts of mods. I'd also recommend having a couple of impellers and a few nozzle sizes. As you make performance improvements you'll need to adjust those too.
    Last edited by theVetteman3; 02-18-2019 at 08:13 AM.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1995 SJ MINT:
    [TBD]



  5. #15
    PWCToday Newbie X2Onthewater's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    It would be nice if people would respect the request of the original poster and try to grasp what his intentions are. We all know that performance pipes offer...more performance.

    From what I read, he is not looking to have a super fast ski, or an easy way to make power, or to know what parts will work best... he is challenging himself to push a very specific list of modifications, to this specific engine, to see how it will effect power. He is doing this to gain experience and knowledge MORE than he is doing it to gain HP. What he learns from doing this will be priceless in modding 2 cycle engines in the future.

    That may be hard for some people to accept, but this is his journey and if encouraged and guided, it may just turn out to be really helpful to the rest of us. (650 owners) If he just pops an other engine in, we don't learn much from that. There are a million things that people have never tried (or tried and not documented) and it would be cool, if nothing else, to see some actual data.

    If all goes well for me, and it probably won't, I plan on building a dyno to test my engine but monitoring the pump pressure is also an interesting idea. The problem that I see with this, or using a torque sensor, is that there are a lot of variables that are hard to monitor. Just as a simple / quick example. If the resistance against the ski changes (more fuel, heavier rider, wind, waves) would that resistance offer a substantial pump pressure change ?

    We need to remember that from stock to a decently tuned engine, it is easy to "see" increases. When you have something that is working pretty decent / tuned well, the resolution of your tests need to be much higher, as your increases will be very small. Eventually, if you keep making steps in the right direction, then you can make substantial increases.

  6. #16
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    Re: X2/650sx stock headpipe differences and modification possibilites

    Why I doubt your comment was directed at me I will bite on this. Really, this kid needs you to defend his thread. You ever heard the expression you get what you pay for. The advice is free. If you don't like it, skip over it. No one is forcing you to read the drivel on here. With that being said. Yes there are a lot of clowns on here spewing drivel. Like anything on the internet, to get any use out of it one must know enough to know the difference between good advice and bad advice. To be honest I do not come here for advice. Yes, sometimes I am looking for information that will save me time on stuff that might otherwise be trial and error. I come on here to share my knowledge and experience for free. I have over 30 motorized vehicles today and have had plenty more in the past. If you don't like it, don't read it. Or explicitly tell me to get off your thread. I will happily oblige, as I am sure most would. Yes, my grammar is bad. You think I have endless time to discuss your problems. You can bet that it I am On here, I am either playing video games or watching my lathe or mill make passes. I am concerned far more about a carriage crash than whether I spell everything right. Thank you to the people that have helped me and I hope I have helped a least a few. This forum has provided some good entertainment and neighborly quarrals, but I do have to admit some of it is getting old.I

    I sincerely hope the OP continues working on motors. It has been one of the most rewarding hobbies i have had.

  7. #17
    PWCToday Newbie X2Onthewater's Avatar
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    Re: X2/650sx stock headpipe differences and modification possibilites

    I was 100%, for sur,e not talking about you. As far as I remember you were on topic and obviously very knowledgable. Your grammar is also on point and very easy to read, compared to most. Well done.

    You are totally right about the background noise when posting anything online / reading anything online. I realize that it is to be expected. My comment was a desperate attempt to help people stay on topic.

    My real concern is that, the background noise often kills the original topic or make finding useful information impossible. My comments, thus far have probably only added to the noise, and I apologize for that.

    I learn a LOT from reading through posts, but I also give up trying to find information in many threads because I don't have the time to read through irrelevant information.

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