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  1. #1
    Steveard's Avatar
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    2004 XLT 1200r power valve not giving power

    I just rebuilt my 1200r engine because of a failed piston. It looked like the ring caugt on the exhaust. Anyway after replacing all the pistons, having the cylinder redone and having the carb rebuilt I am still struggling with low power across the board and a reduced top end. it peeks out on the tach at about 6300 RPM and 51 MPH per speedo. I did the setup and tests from the maual for the PV and it apears to be fine. I took a ride with the fron seat off and notice that the PV was not moving very much (mostly starting to shutter) when at full speed. I pulled the PV cables off the motor and rode pulling them manually. I found that the engine worked best at all RPMs with the PV in the down position. When I would pull it open at full RPMs it would bog and dropped to about 4500 RPM and 35 MPH. I checked the valves are still connected and I do have the waveeater clips/couplers. My best gues is that the carbs are not working right or that the reed valves are leaking by. I am not certain if these would cause the issue. I did not replace the reeds during the rebuild so I am leaning that way.

    Any thoughts on why the engine does not run well at high RPMs with the PV pulled up?


  2. #2

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    Need more info.

    Start with carbs:
    jetting, high and low speed and how much the adjustment screws are turned out
    pop off
    needle and seat

    compression

  3. #3
    Steveard's Avatar
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    The carbs were sent to Oside for rebuild. I did not ask to have the tamper caps removed so it should be stock. Comp is 120 on all cylinders. The only changes from stock I have done are the D-Plate and wave eaters

  4. #4
    Steveard's Avatar
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    I was looking to buy new reeds to see if that fixes this issue. I was told by a friend who races to get Boyesen reeds. The problem is I cant find any of their or others that say they fit my XLT1200. Any recomendations as to where to find the ones for this PWC. The ones I did find were part of a kit they were the "Boyesen Reed Valve Stuffer Kit - Yamaha PV 1200/1300". Any thoughts on these? BTW I am not looking for race performance. I just want a solid boat with good bottom/Mid end performance.

  5. #5
    Steveard's Avatar
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    Any ideas on this one?

  6. #6
    Steveard's Avatar
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    Ok I pulled the reed valves today and took a good look at them. 2 sets looked perfect and the one from the blown cylinder had a little wear right at the end (maybe 1/4mm at most) but did not look not look like it would cause any leaking or issues. I replaced all three sets with new OEM ones. When I pulled them out there was a lot of oil on them that I had to clean off. Still not sure if this can cause the PV issue I noted above.????? BTW if anyone is interested I have 2 good sets of reeds and one that is so so.

  7. #7
    Steveard's Avatar
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    I took it out for a ride today and it did have a lot more power with the new reed valves installed but it still is not back to where it should be. It stutters a little bit when first hitting the accelerator and is topping at about 6200 RPM and 53 MPH per the speedo. When I pull the plugs they look prety dark and it while out my oil alarm went off when I was riding for being low when I know it should have lasted longer. I am guessing that the oil pump setup was messed up when I was messing with the idle.

  8. #8
    Steveard's Avatar
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    I did have to adjust the oil pump setup quite a bit to get it back to the correct position. I took it out after and it worked about the same as the last time out but with quite a bit less smoke coming out the exhaust. After about 5 minutes one of the cylinders stopped firing. After getting it back I found that the front cylinder spark plug had melted down. :< (. When I got home I checked the comp and it is still reading good across all cylinders. I have removed the plugs several times to pull the exhaust in and out and may have bumped this one closed is my best guess. I have new plugs now.

    With this I still have 2 things that I cant figure out. the WOT RPMs top out at about 6200 when I believe they should be around 7200 and when I manually move the PVs for the WOT condition the engine chokes out. Any ideas? I am starting to think there may be an issue with the rebuilt carbs.

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