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  1. #1

    Power Valves Not Kicking In

    I'm having problems with my XR1800 that has two 1200r motors. I am veeeerry frustrated. I spent a week cleaning the power valves and they turned very easy by hand. Tested the servo motor and it worked and cycles after motors turns off. Took the boat out and still only got 5 1/2K rpms and top speed of only 45. The power valves don't kick in like the other engine. Because the other engine runs well, I had to steer far to the right to keep the boat straight and I couldn't make sharp turns to that side. Here are the usual suspects.

    1. The engine - I had the engine rebuilt by the dealer last spring with a new crank, three new pistons and top end. I have not pulled the head this year. The only suspicious sign is the spark plug on cylinder one is very clean compared to the other two. I have even compression and no water leaks.

    2. The Servo Engine - Even though I tested the servo engine, and it seem to be working fine. But, it is not kicking in at higher rpm's like the other engine. Maybe replacing the servo motor would cause it to kick in at higher rpms.

    3. The Carbs - I had the carbs rebuilt in the spring of 2010 by the dealer with Mikuni kits. I replaced the pilot jet to 95's in the spring before I took it out of winterization. I have cleaned the carbs at least four times this year. I have tried various settings on the low and high end screws. I have no bogg and it starts and idles easily. Maybe it's some bad carb voodoo with the needles, diaphrams, or something else that I haven't found yet.

    Obviously I am grasping at straws on why my power valves aren't kicking in. Osidebill told me this in an email "there is nothing to prevent the highs(main jet) from "enagaing" as you say. They simply work on vacuum, pull enough vacuum fuel is drawn from the jets." I am obviously not pulling enough vacuum, but I don't know why.

  2. #2
    By the way, I have Waveeater clips and couplers. I also have D-plates with temp sensors.

  3. #3

    Join Date
    Jan 2006
    Texas City, Texas
    Your engine does not get high rpms while it is pulling a load in the water, but how about when it is out of the water?

    The issue is that you may not actually be generating enough rpms for the valves to open. At what rpm do the valves in the other engine open? If your valves are supposed to open at 5800-6000 rpms, then there would be no reason for them to open at 5500, the rpms that you say you are running. If you pull it out of the water, and then rev the engine, with no load you should be able to get it above 6000 and the valves may open then. If this were the case, then you would know that there were nothing wrong with your valves and you would focus on other things like that suspicious plug..... In other words, the valves may be a symptom of a problem, but not the problem at all.

    About the plug.... under a load you might have a slight cooling water leak that washes your piston and keeps it clean (and plays hell on combustion). If it was running well after the rebuild, it is possible, but unlikely that some bolts loosened up causing a water leak. It may be worth your while to retorque the head and base bolts. This happend to me the first year I had my GPR. Did it ever run well after the rebuild?

    Switch servo motors with the other engine to verify that the "bad one" really is bad.

  4. #4
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas
    How to check servo motor:

  5. #5
    The engine ran well after the rebuild last summer. I am going to pull theh head and look at that cylinder closer.

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