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POWER POWER???

Discussion in 'The Garage' started by mitchxc700, Apr 9, 2012.

  1. mitchxc700

    mitchxc700 mitchxc700

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    Lookin for the best all around power set up. Single carb, 2 into 1 exhaust? dual carbs twin pipes? not sure where to go. im lookin to rephase and do some porting work. Anyone out there know anything about making power?
     
  2. Poverty

    Poverty XS650 Addict

    sell your xs to me....buy a bigger bike .... best power upgrade on the market Guaranteed!!
     
  3. You have no idea how much you're asking for, or how much nonsense you're going to have to wade through when you get responses! For sound information, follow the link at 650 Central and get yourself a copy of Craig Weeks' performance manual.

    First, there is no "best" setup. You don't try to run a drag motor on a short track, for example. What's best is what meets your goals, which are not defined in your post.

    To address specifics, single carb conversion is not the way to make power on these motors, and off-the-shelf 2-1 systems will not deliver a power increase until close to redline. For the street, the optimal exhaust system with the old twin, whether at stock displacement or punched to 750, is 1-1/2" dual exhausts of 32" to 36" length (at the center line, as measured from the valve face) with good free-flowing mufflers. Straight pipes will deliver an increase only in a narrow rpm range; on the street they're effective for getting attention (of the wrong kind, IMO), but not for making power. The venerable Shell #1 grind cam is a good choice, and Megacycle has a new grind out that's been getting some fine reviews. Avoid that XS Performance cam from Mike's like the plague; been there, done that, and will be reinstalling the trusty Shell #1 as soon as time and energy permit. Re. porting, Jack and Craig have some fine work posted, and a little looking will turn it up.

    PM if you have specific questions, Mitch; it's gonna get piled pretty deep on this thread, so I'm getting out of the way!
     
  4. Classic

    Classic rackin' up the miles

    No replacement for displacement.
     
  5. Poverty

    Poverty XS650 Addict

    Sure there is ...and its generally cheaper ..

    [​IMG]
     
  6. The replacement for displacement is newer technology. There are only two good reasons for hopping up the old twin motor--racing and personal satisfaction. If you do it right you'll be out more money in a hotrod XS than you'd pay for a good used SV650 Suzuki twin that delivers as much out of the box as the XS650 cases will take with full race mods. Pov, that turbocharger may be cheap, but as you're probably well aware, it'll shred the rods and separate the flywheels in an XS650 if the buyer actually uses it, unless race rods and welded crank are in place.
     
  7. Marvelicious

    Marvelicious Naturally Aggravated

    I suppose if we're looking for the cheapest ticking time bomb to make some numbers, the blue bottle would make you go like a SOB, right up until it came apart. To actually make it stand up to that; well, you'd have to spend just as much money as it would take to make a motor stand up to boost or bump up the displacement.

    I get the feeling that we're overshooting the OP's goals here though. I think maybe he's asking about the best bang for his buck on a basic rephase/rebuild...
     
  8. We brag power but drive torque - for typical street/highway use, mod's that fatten the torque curve in its midrange are what you are most likely to actually "feel" when riding. Grizld1's description of the optimal exhaust system is one example. Somewhere a long time ago I read that measuring exhaust pipe length around the "outside" of the curve from the flange is a good approximation of a centerline measurement from the valve face - can anyone else verify this?
     
  9. Michael Morse suggests that formula for length from the valve face, Aldo. It gets you as close as you need to be.
     
  10. bradshaw106

    bradshaw106 XS650 Addict

    I always thought a good running xs with stock gearing went pretty good
     
  11. gggGary

    gggGary Old guy, NO expert.

    We need a picture of YOU. Often the best way to improve performance is obvious.:D
     
  12. Classic

    Classic rackin' up the miles

    I have to agree.
     
  13. See what I mean, Mitch? You ask for information, and the Peanut Gallery tells you why THEY don't need it. Come on, guys, let's have some more useless, uninformative noise.
     
  14. mitchxc700

    mitchxc700 mitchxc700

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    hahaha ya i can see that, im not putin NOS on my bike, (all ready done on my sled) im not going to turbo a xs650. where i live i never see these bikes, so im building a bad ass bike thats not going to cost me 80 grand. Now having said that i wanted to give fourms one last try but grizld has a point and i dont know anyone here that knows anything about these.
     
  15. racerdave

    racerdave V Gone not forgotten V

    Mitch, what year XC7 do you have?
     
  16. Marvelicious

    Marvelicious Naturally Aggravated

    Well its a pretty loaded question. If you go onto a Chevy forum and ask what the "best all around power setup" is for a 350 is you'll get a shit-storm that'll make this look tame. If the answer was simple, we'd all have the same setup and this forum could be entirely replaced by a simple wiki page. I'm no expert on these motors and am firmly in the "peanut gallery" as far as that goes, but this isn't my first rodeo as far as modifying a vehicle or sorting through internet forums to get what I want.

    Since there is no "one size fits all" answer, you have to ask yourself first:
    1 how much are you prepared to spend?
    2 what kind of riding do you plan to do?

    Answer those questions for everyone and you will probably get a lot more useful answers, but there is simply no substitute for spending some time reading.
     
  17. I could not agree with you more grizld1 well said. Better than power fix the short falls of the bike get it to handle and stop lighten it up remove excess weight. Better to do before the monster motor. :thumbsup:
     
  18. xjwmx

    xjwmx XS650 Guru

    Are you aware that there's a bolt on 750 kit? I think Mike's sells a version that people are happy with. Regarding all the porting and polishing and tuning and swapping parts, and the more radical strategies, I've yet to see one dyno result from it posted here, and that can only be because it would be embarrassing considering the time and or money invested.

    It occurs to me that personal satisfaction and "racing" are the only two reasons people do just about anything :) The actual general consensus is if power for its own sake is the thing you're after, consider a bike that fits your style better. I ride an XS650 because it's easy and cheap to keep it running. And good-looking, to me. And interesting to other riders who see it. And...
     
  19. Searching for max power with this mill will result in broken engine parts and, like the man said, a stock SV650 puts out as much power off the shelf as an XS650 tuned just this side of a hand-gernade.

    But, in a nutshell ( and repeating somewhat) the "best" power for this twin is broad (rather than peak) power. The tried and true basic formula is: hotter coils, VM34's* with set-back intakes and long K&N filters, Shell #1 cam with stiff springs, 750 cc's (compressed to taste), exhaust headers with max ID of 1.5" and clean up the ports (just clean the casting flaws - don't remove much material)**.

    You can do all that with out splitting the cases and you'll be ok if you don't exceed stock redline.

    If you are going to spin it you need to weld the crank.

    If you are going into the bottom, swap in the extra tooth fifth gear so you can run a bit lower ratio sprocket set and still have reasonable cruising.



    *The CV type 38's on the early models are OK too and a minority of people prefer VM 36 in racing situations

    ** a FEW people can improve the breathing of this head (e.g. Jack) but most will make it worse.
     
  20. uebe

    uebe XS Goober

    Burns - Excellent, well written post. Is there some way to save or "bookmark" posts on this forum?

    xjwmx - Always appreciate your opinions..................

    ........altough we may have lost mitch..........mitch?.....you out there?
     

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