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Thread: CAMs ???

  1. #1

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    CAMs ???

    Has anyone tried cams without changing pistons? The RIVA offshore kit involves cams, pistons, and an ECU but runs on race gas 109 or better. This mod by itself, let alone the fuel costs, is not an option. My quest is to find cams that allow use of pump gas that wil produce more RPM thus more speed. I have not seen any street bike posts on this ( this is just a street motor in a watercraft) BUT will this mod require an update to the ecu? Kawi is very protective of their ECU's. Aftermarket ecu's not readily available.


  2. #2
    cams im guessing no on those. riva custom grinds rewelded stockers and wont give out the spcs on them. as for valve lift the pockets on the stock psitons dont allow for much more and still have safe clearences. unless you pulled your pistons and had them pocketed to allow more clearence but then you loose compression. thus hindering a bit of power.i dont think you would need a reprogrammed ecu and if you did they cost a bit of $$. you probably could get away with a powershot fuel tuner or just letting the fuel system recalibrate. to gain the most from this you would also need a good ram air,intake,ported intake runners,ported head,and honed exhaust manifold. when building a high power n/a small displacement engine the key is to keep air velocity high. so with this in mind the need for a tuned length intake tract,proper placement of a velocity stack and HV porting would be required. your porter would need to know what hes doing as just flogging the port(making them larger) will not show the performance you want. it could infact hurt performance by lowering air velocity.

    do i think you could do this? ya i do,it would just take some time and having the motor ripped down more then once.not to mention with a topend grind you could loose quite a bit on the bottom end. would it be worth it? i think it could make a 200hp n/a engine. is 200hp worth it? by the way stock cams to buy out are 500-600 a piece+welding and regrinding

  3. #3
    AaronC's Avatar
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    I was strongly considering doing cams but everything is a guess at this point and without tuning it's all worthless. First you'd need to know the stock specs or send the cams out and have them put on a cam dr. or degree them to find the specs. Then you can do the same with the Riva's to find the specs on them or what I was gonna do is look into making my own customs from comp cams. I designed several of my own for my mustang. Lift won't be the issue with P/V clearance because the valve's are no where near the piston at peak lift, but choice of lobes (ramp rate), LSA, ICL, etc will affect it and doing your own custom cams you can figure this out. After you get all this sorted out you need to make sure the valvetrain is strong and stable and that you can properly tune the motor or it's not gonna show the gains it should. In the end, it seems like a lot of money for the gain.

  4. #4

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    I was wondering about this just a few days ago. Forgive an RXP guys' ignorance, but it seems to me like it wouldn't be terribly difficult to retrofit some of the ZX-12 or ZX-14 stuff to the STX12 or STX15R.

    A few months ago, we swapped a set of Ninja 500 cams into an otherwise stock Vulcan 500 and the difference was astounding. The difference in the quarter mile was nearly 2 seconds and 13 mph, while top speed went up by about 25 mph.

    I wonder if you can swap a set of ZX-12 cams and throttle bodies onto the STX motor. You could even swap the ECU and harness over to enable the 10,000 rpm needed to reach peak power. The bike ECU doesn't know it's not in a bike. It may even work with the jet ski harness with a few wiring adjustments. Of course, a "special" prop would be needed.

    For comparison, the ZX-12 makes about 180 hp @ 10,000 rpm at the crank, while the ZX-14 does about 195 hp @ 9250 rpm. I think the STX12 and 15r make 140 and 160 hp, respectively. A 40 hp boost is nothing to sneeze at. The ZX-12 cams are probably more aggressive than the 14's, so it would be most interesting to see a set of ZX-12 cams in an STX15r.

    You'd also be surprised how cheap you can find that stuff on e-bay. I scored the Ninja 500 cams for $10.

    Mike

  5. #5
    I was also wondering about itb's and cams a few weeks ago but figured it was too crazy of an idea. I guess not.

    There are some things to remember though, motorcycles thrive on high compression that the 12 and 15F's don't have. Alot of cam and itb setups rely on the high compression to allow for maximum power potential. When you spin a motor to 14k+ rpms that puts alot of stress on the rods and more specifically the rod bolts. The question is can the rod bolts on the 12 and 15F rods take that kind of rpm? Also, how is the oiling system in the skis?

    Not sure if I made some valid points, but I just thought I would throw that out there.

  6. #6
    the guy thats been helping me with my turbo said the cams from the 12 might not fit. due to journal differences and different cooling passages(a defferent head). he also said after looking through specs and the internals said that he would not allow me to spin past 9k. he said safer but still dangerous on stock internals would be around 8.6k. spinning these motors high just doesnt seem like the way to get more power.

  7. #7

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    Quote Originally Posted by racingtrx450 View Post
    ...he also said after looking through specs and the internals said that he would not allow me to spin past 9k. he said safer but still dangerous on stock internals would be around 8.6k. spinning these motors high just doesnt seem like the way to get more power.
    That's weird because the ZX-14 makes peak power at 9250 and redlines at 11,000. The bore x stroke is 84 mm x 61 mm. The STX15F is 83 mm x 69.2 mm. In keeping the same piston speed of the ZX-14, the rpm limit of the STX15 would have to be about 9.7 krpm.

    Hmmm. . . wonder what exactly he's worried about.

    Mike

  8. #8
    i have no clue. maybe the stock 15f internals arent designed to be spun to what the 14 is designed to. not to mention the jetski holds its top rpm constantly for as long as the throttles opened. the bike has gears meaning your not constantly reved out. if you want to spin it to 10k do it. let me know how it goes and how it all holds up. if everythings fine then we have an new way of creating power from these skis. im just gonna stay safe and not use high rpms to squeeze out power. more rpms= less reliability. im no newb to motors. and ive seen plenty of failures when you spin motors too high or even to where the factory says its safe.
    Last edited by racingtrx450; 08-07-2007 at 03:41 PM.

  9. #9

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    Quote Originally Posted by racingtrx450 View Post
    ... if you want to spin it to 10k do it. let me know how it goes and how it all holds up...
    I would, but I don't think those ZX-12 cams are going to fit my 4-tec.

  10. #10
    that a valid reason lol...well if someones willing to pay me labor and parts ect. i will gladly do testing and tuning for a good cam set up.

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