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Thread: loosing rpms

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    southernstateofmind's Avatar
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    loosing rpms

    ok, i'm new, i've searched all the forums and can't find what i'm looking for. checked plugs, fuel filter and compression. bought an 01 gp1200r, already modified. it was running 7100 rpm, over the course of running it for 4 to 5 hours, i've lost 1000 rpms. what do i need to start looking for/ inspect/replace? not afraid to tear into it just need to know which way to go, just not aimlessly disassembling. thanks.


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    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by southernstateofmind View Post
    ok, i'm new, i've searched all the forums and can't find what i'm looking for. checked plugs, fuel filter and compression. bought an 01 gp1200r, already modified. it was running 7100 rpm, over the course of running it for 4 to 5 hours, i've lost 1000 rpms. what do i need to start looking for/ inspect/replace? not afraid to tear into it just need to know which way to go, just not aimlessly disassembling. thanks.
    make sure the power valve servo motor is working, When you shut the motor off you should hear it cycle. Or you dropped a power valve and is resting on the bottom of the exhaust port, or a power valve pin came out.

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    southernstateofmind's Avatar
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    awesome, thank you. i'll look there tomorrow after work and let you know what i find.

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    southernstateofmind's Avatar
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    need a little advice on which way to go... dropped a PV, 3rd cylinder was severely starved, there was rust in the PV box, barely any oil. should i 1) piston, jug, new PVs and have carbs done, or 2) whole engine, lock, stock and barrel?

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    southernstateofmind's Avatar
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    this is what was left of the #3 PV.Click image for larger version. 

Name:	IMAG0663.jpg 
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    Almost's Avatar
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    Sorry to hear that, I'm going to go out on a limb and guess that Wave Eaters have not been installed? How many hours are on the motor? At the very least you are going to want to get the crank inspected. Depending on how many hours are on it you might only need to get that one cylinder re-plated. Carbs are a must, the last thing you want to do is rebuild it and have it blow up because you thought the carbs were good. Take as much guess work out as possible and make sure everything is within spec. Don't just assume it is.

    Find a service manual it will help tremendously.

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    mudslanger's Avatar
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    Quote Originally Posted by southernstateofmind View Post
    this is what was left of the #3 PV.Click image for larger version. 

Name:	IMAG0663.jpg 
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ID:	299194
    That looks like an R&D power valve from the pin lever. I've had a couple skis lately that had an R&D valve along with stock ones and the R&D one failed. The stop on the power valve shaft were battered up from the valves closing and pushing against the stops. Just wandering if the distance from the pin to the stop could be a little longer on the &d than stock. Got to order some so I guess I'll be checking that before I install them.
    Another thought could be they are just not as good a quality metal as stock.

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