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Thread: mild cams

  1. #1
    timkellogg
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    I wonder if anyone could give me an idea as to the rpm range you get out of a stock z1 with drop-in cams like a web #118. Also, I'd like to know how much that range moves down for a given amount of overboring. I'm new to tinkering with bikes and can't afford a lot of trial-and-error in my engine building. so I could use someinsight as to what qualifies as mid-range and top-end for certain z1-based engines. Thanks in advance for any help.

  2. #2
    Tony O
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    11000 rpm no problem. Bike will still rev. with the bigger bore.However larger bore meens more low end power.

  3. #3
    Member S2LR's Avatar
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    You may get 11000rpm out of the motor but the motor will nose over long before that if you're using a stock head with these cams. The #118 cams are pretty small (.365" lift) so you would have to get some larger cams and more head work to push the power all the way to that rpm.


    The cylinder head setupreally determines the rev range of your motor. Putting in a larger (lift & duration) cam will raise your rev range, but only to the extend that your valve and port size will support. In other words, a huge cam will only take you to a certain point before the valve/port size becomes the choke point in your flow.


    Increasing bore size willreally only change your power curve if you don't modify the head to compensate. It won't have an appreciable effect on rev range. The increased bore sizewill move the torque down so that you have more low end and midrange.


    As far as motor combinations, I know some that might work for you but you need to provide more information on your current motor setup as a whole and what you want to achieve...



  4. #4
    timkellogg
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    Right now I'm limited ($$$$$) to putting my stock 900 back together with fresh rings, cam chain and tensioner and a clutch to replace the one that shattered a plate and filled the pan with chunks. The bike was a garage sale find that ran good but may nickle and dime me to death with all the non-motor stuff it needs. I thought I might be able to spring for getting the crank welded in preparation for later, possibly the #118 cams, but I'm mostly trying to learn some things to apply after I ride the stock (or slightly over) 900 a while and save up money for more.


    As far as how much they'll rev, I'm more concerned with how far up or down the tach the hp and torque peaks move (8500 and 7000 rpm to...) than actual max rpm. I'm a recent convert from Fords and Chevys, and cam makers for those usually give at least a rough idea of rpm range for a given displacement, while the bike cam makers saythings like "strong midrange and top-end". For a guy who's only ridden stock bikes, where the redline on the tach actually relates to the engine under you, that's a little vague. I'm looking to eventually go to a 1200, with head work and all. Right now I'm riding a 400 Yamaha (when it's not so cold out)and getting my Kaw back together for spring (I hope).

  5. #5
    Member S2LR's Avatar
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    If it's a choice between the cams and the crank, I would invest in the crank. At this level, reliability is more important than performance.


    The cam makers for bikes are vague because of the plethora of motor combinations and cam timings that are used with their cams. Cam timing alone can have dramatic effects on your power curve. Unlike the typical Ford or Chevy V-8, you can mix and match cam grinds on bikes on both the intake and exhaust which muddies the water even further. I've seen guys run some pretty strange cam combos.


    If you change nothing to your motor except your cams, you'll get maximum power around 9500rpm using a standard cam timing setting. Sometimes the only way to find out where the powerpeak is, is to ring the bike until the power drops off. Then you will know...[img]smileys/smiley14.gif[/img]

  6. #6
    timkellogg
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    Thanks! Yeah, I was ranking the crank as a first improvement, beyond the big oil cooler (with fan) I already have. Reliability is my big concern, since I get very little time on the bike beyond my 30-mile commute to work, and would like to travel on it a bit when my wife and I both have bikes we can trust to get us places. If I ever can get to the 1200 level with it, I'd like to keep that sort (1000 over stock) of powerband, with the best setup I can put together for a daily-highway-rider/ antique sport-tourer. I'd appreciate any advice along those lines regarding head work, cams, and other upgrades, so I know better what to plan andsave up money for. Since I can't afford to do much yet, I figure I should spend my time studying the subject to avoid wasting money when I have it to spend. Thanks again for the help!

  7. #7
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    For what you want to do and your budget, here's what I wouldbuild if it were me...
    <UL>
    <LI>Bore stock block to 1197cc and use 10.25:1 pistons.</LI>
    <LI>APE manual cam chain tensioner.</LI>
    <LI>Street/strip port on the head with 3-angle valve job. Stock valves should be fine with this, but if you can afford it, go 0.5mm oversized stainless valves on intake and exhaust. Use the #118 WEB cams with this combo with shim under bucket setup. Use the recommended cam timing. (The cylinder head is the key to good performance so investing here isa wise move).</LI>
    <LI>Welded crank</LI>
    <LI>Aftermarket exhaust with 1.5" primary tubes.</LI>
    <LI>If you can get them, I nice set of 29mm smoothbore carbs with K&amp;N filters.</LI>
    <LI>A good aftermarket ignition if the budget allows...</LI>[/list]


    This setup will be very streetable, reliable, and need very little maintenance (other than an oil change). It will also give you a little kick when you want to twist the throttle...[img]smileys/smiley1.gif[/img]

  8. #8
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    Forget the oil cooler,it will do more damage than it helps. These bikes only have 6 to 10 psi oil pressure and reducing flow through the cooler does not help. Just use heavier oil if it bothers you,like 20W50. I have never seen what could be called oil related failure in any of these bikes,stock.

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