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  1. #1
    ride-blue's Avatar
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    Please Help, detonation RXPX 260.

    Iíve lost my 2nd top end since making it a stock class. The rear piston got toasted and bent its valves. Boats history: all stock with 60hrs. Then made it stock class. R&D intake, R&D fuel pressure regulator, Riva fresh water cooling, valve retainers, new clutch washers, Less Cook ECU, Less Cook scat prop. Runs 74mph at 8700rpm on the skis gauges. Then the fly wheel bolts broke pretty quickly. Tore down motor and installed new main bearings, rings and the better fly bolts. The mechanic also retarded the cam 4 degrees, or one tooth back, says he does it all the time works great for more compression. Well it lasted about 2hrs and rear piston detonated. Took it all apart, got 1 new piston, rings, valves, and hone. Cam still at 4 retarded. Blew up again in about 1 or 2hrs. The first time I figured not enough octane gas probably in the low 90ís. This time I was using 100octane AV gas. Same thing happened again so what do you think Cam, ECU, or ??? Thanks.
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  2. #2
    quiddo15's Avatar
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    Have you been monitoriting Afr's? Les cookes ecu run very lean on his recommended 58psi.


  3. #3
    dpracing's Avatar
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    Cam one tooth back runs better is wrong. What are your afrs?

  4. #4
    ride-blue's Avatar
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    No never checked them. Thanks.

  5. #5
    dpracing's Avatar
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    Quote Originally Posted by ride-blue View Post
    No never checked them. Thanks.
    This could be the cause, you need to monitor AFR's


  6. #6
    Water4fire's Avatar
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    My Les Cook ECu for my conversion was way lean. I had to bump up fuel pressure.
    And I am sorry to be abrupt, but moding a ski with out monitoring was not a good idea. A $160 dollar set up could have saved lots of cash.


  7. #7
    I would never consider tuning one of these motors without data logging. CMD, Vtech, Motec, Megasquirt... it really does not matter much on the fuel side. They are all way better than the other options. Regarding catching detonation, some of these options are much better than others.

    Andy

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  9. #8
    ride-blue's Avatar
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    Yea, apparently I am learning the hard way. (my first 4stroke) Thank you all keep them coming.

  10. #9
    boost junkie skidoochris's Avatar
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    no afr.... . wtf
    you can not run a boosted motor on a "tune"
    every motor is different, different altitude, different fuel, different mods
    you learned a good lesson..... get a real data logger

    four strokes are very forgiving compared to a 2 stroke
    but a boosted 4 stroke with a race ecu and no data =

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  12. #10
    I would change the mechanical, you can not go wrong for 4 times, the friend says as many variations exist between the operation of the bike, altitude, humidity, temperature, gasoline, etc. Then the thing I do not understand, because if you want to get more compression must delay of 1 tooth distribution? doing this will not improve your performance on 4 tech but you'll only problems. we constructed modified engines that run at 9100 rpm with all stock also phase motor, and in any case if my friend Andy gives you advice subbito take them on the fly, he and a great motor for eletrŰnica.

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