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Thread: Power Valve ??

  1. #1
    OLD # 7 IEGPR's Avatar
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    Power Valve ??

    Can someone tell me why my o6 gpr dose not have power valves??


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    Crash Test Dummy Smitty's Avatar
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    They got rid of the powervalves in 2005 or 2006... trust me, you are better off without them. Your are pumping 170 HP vs the 155 of the origional 66v motor, so you have increased reliability along with increased HP.

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    OLD # 7 IEGPR's Avatar
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    Question

    OK, So if you are going to build a bas @#$ motor you would still want carbs but not the power valve. Has anybody stated switching over to non PV cylinders??

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    Crash Test Dummy Smitty's Avatar
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    Not an issue for you, since you don't have powervalves. A little history here; powervalves open and close to change the size of the exhaust port. The large ports in a 2 stroke restrict power at lower RPM's, so the powervalves are closed then. They open up at higher RPM's and increase power. In 2005 Yamaha eliminated them without losing power.

    The problem the powervalves had, especialy in the early years, was that the powervalves would sometimes fail and slip down into the cylinder, where the piston would hit it on the upstroke and self-destruct. There were several fixes for this; waveater clips are an inexpensive, simple fix.

    Some of the big bore kits lock the valves in place, elimitating the possibility of failure. Others keep them. If you are wanting to build a badazz motor, start researching here and talking to the gurus; figure out what your goals are and go from there. When they first came out the the Electronic Fuel Injection (EFI) for the GPR, people were pulling them off and replacing them with carbs; but now people are getting to know the EFI well and how to tune it. There are people with 80mph EFI boats out there now, and rumor has it they are about to make triple pipes for EFI boats.

    So how fast do you want to go and how much are you willing to spend is the only question!

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    My 1400 (ported) had no PV's and let me tell you it was a dog until it the power band and guess what it came on like a frieght train..... The problem is where you want to cruz at is where it wants to come on the power band so it tries to jerk you right off the seat, the power valves would help soften that..... Just my experience and my 2 cents


    Whats up Smitty?????????

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    Hydrotherapy's Avatar
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    Quote Originally Posted by lvnspeed View Post
    My 1400 (ported) had no PV's and let me tell you it was a dog until it the power band and guess what it came on like a frieght train..... The problem is where you want to cruz at is where it wants to come on the power band so it tries to jerk you right off the seat, the power valves would help soften that..... Just my experience and my 2 cents


    Whats up Smitty?????????
    all of above true,its a personal prefrence either power valve or non power valve, for me the choice was easy as i bought a new 05 and had no choice as they came without and i love them..basic rule on a 2 stroke is less moving parts the better,saying that if i would of had a 04 would still be happy but its another possible weak point or a further component that needs maintance,yes the power with a power valve engine is smoother and better to cruise and does seem to give a better low down feeling of pulling a little smoother on bottom but how many gpr riders go for as sunday cruise,if you got valves you will love them if you dont you wont miss them,
    for me its the diffrence between my old RD350LC proddy tuned against my newer RD500LC ypvs motor stan stevens stage 1,the 500 was fast and pulled well all over and was ridebly every day to work or play but if i wanted to go out have fun pull wheelies and rip up some green lanes it had to be the lower power 350 as it came on song fast and when it came on power it was like a switch all on in one go and kept you working it to get the max..
    either way there all fun just pick your weapon

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    OLD # 7 IEGPR's Avatar
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    Thanks guys for all your input. The reason I asked is I have a spare motor with pvs that I plan to build soon.

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