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Thread: 650 Porting

  1. #1
    I dream skis naticen's Avatar
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    650 Porting

    I'm doing some porting on my 650 and was wondering if anybody had any numbers or patterns to help out. I've got a cylinder that had some done, but everything is raised. I'm going to match for widths but wanted any input I could get.

    My motor has an sbn44, 30cc domes, westcoast pipe, and drilled waterbox. I think the bore is 76.5 with wisecos

    I'm looking for all bottom end power
    Last edited by naticen; 04-24-2012 at 08:44 PM.

  2. #2
    PWCToday.com Is My Home Away From Home jetman624's Avatar
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    Re: 650 Porting

    Best $50 you can spend right here:

    http://www.pwctoday.com/showthread.p...t=#post3487005

    Won't give you the keys to a fire breathing monster, but lots of useful information in those.
    '02 SXi Pro: Factory Limited pipe, ported SXR cyl, SSP stearing system, WORX ride plate, skat trak intake grate, blowsion tubbie II, 3DR SS hull extensions, 3DR trued hull, 3DR pump shoe mod, bored pump nozzle

    '92 X2: Mostly stock, except for the 750

    '91 X2: #718

  3. #3
    I dream skis naticen's Avatar
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    Re: 650 Porting

    Ive read some 2 stroke books and I felt like the keys were in there but they were just too vague or too intense with math that I never feel like doing. I'm gonna try this book out after reading those reviews. Hopefully it'll leave me with more applicable knowledge than the other books I've tried.

    I'd still like some cliff notes (patterns or measurements) to compare what I'm thinking with what others have used.

  4. #4
    PWCToday.com Is My Home Away From Home
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    Re: 650 Porting

    Spark notes ftw
    89 rockerd X2, ported and polished 65 SOLD
    93 waveblaster 701 SOLD
    Fix'd steer 650sx ​SOLD
    100% custom X2 project

    Originally Posted by JonnyX2
    One kick is maintenance....twice is abuse

  5. #5
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: 650 Porting

    ive heard on average to widen the exhaust port to about 70% of the bore size..what you would want to do is get some thicker paper and line it up in the cylinder, then get a pencil and trace out the port shape inside the cylinder.. measure out the desired total port width on your paper then cut it out and scribe the lines out in your cylinder..then grind to your lines.. this is called mapping your cylinder.. im planning to port my 550 reed cylinder and this is how i plan to do it.. heres an artical to look into..http://www.macdizzy.com/cylinder_map2.htm i will say it does get pretty complicated towards the bottom.. it goes into great depth but will give you an idea
    91 440; PJS Viper 7000, jetsport exhaust mani, factory full pipe, coffman waterbox,solas 17*, jetco worked 440 pump, ocean pro nozzles. shredmaster ocean rideplate and grate combo, wide tray, footholds, deep strake mod, driveshaft fill,650sx quick turn

    build thread part 1: http://www.pwctoday.com/showthread.php?t=331343
    build thread part 2: http://www.pwctoday.com/showthread.php?t=364872
    build thread part 3: http://www.pwctoday.com/showthread.php?t=396154

  6. #6
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: 650 Porting

    70% is totally safe. At 76.5mm bore diameter, 70% would be 53.5mm wide. This will increase port time area while raising peak rpm only slightly. if your looking for bottom end power do not raise the exhaust port. If you have the ability to raise the transfers there is more power to be had there as well.



    Home of Newmiller Machine

  7. #7
    I dream skis naticen's Avatar
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    Re: 650 Porting

    Thanks for the input. I read that link. I put that into the category of too much math. I feel like you do all that work and it's still only pointing in the right direction. I guess there is no right answer and it depends on what exactly you want. I just want to get what I can out of it without losing much power anywhere else.

    I can raise transfers as well. Should they be widened or just raised? I can't remember off the top of my head, but I think the ported cylinder's are about 2mm higher than my stock one. I don't think they are much wider if at all, but I haven't thrown a snap gauge at it or mapped it out. I'm gonna do both and see.

  8. #8
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: 650 Porting

    the article goes in depth about degreeing the engine to find when the ports open like you would on a camshaft for a 4 stroke engine.. it also lets someone who understands it know where they can modify the port to change the powerband and such.. but just to make a template, doing the first few procedures will do what you need to do to get a template made...
    91 440; PJS Viper 7000, jetsport exhaust mani, factory full pipe, coffman waterbox,solas 17*, jetco worked 440 pump, ocean pro nozzles. shredmaster ocean rideplate and grate combo, wide tray, footholds, deep strake mod, driveshaft fill,650sx quick turn

    build thread part 1: http://www.pwctoday.com/showthread.php?t=331343
    build thread part 2: http://www.pwctoday.com/showthread.php?t=364872
    build thread part 3: http://www.pwctoday.com/showthread.php?t=396154

  9. #9
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: 650 Porting

    Raise the transfers 1.5mm. Like already said, if you want low rpm power do not raise the exhaust. Raising the transfers will decrease blow down timing and will effect the way the power comes on. The amount of work involved widening the transfers is not worth the small power increase you will get and you can't do much with the fifth ports anyway as the ring ends will be exposed.
    fairlane is correct, it is all about degrees of crankshaft rotation... I am just converting degrees to mm for you, if you want it in degrees I can give that to you also. However, unless you are using a degree wheel degrees will not do you any good.



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  10. #10
    Top Dog Bruce in SB's Avatar
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    Re: 650 Porting

    Just send it to mcn6 ... money well spent! All done on a computer program and beautiful work...
    "Thanks" to Chris Newmiller @ Newmiller Machine

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