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  1. #1
    urugol's Avatar
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    GP1200R Fresh Build Need Some Advice

    Hi all,

    I finished my 1200r rebuild a few days ago, and went out to the lake to run the engine in today. I have done a couple of Polaris' this is my first Yami. I have a few things going on, I will describe the symptoms and attach pics if anyone has any ideas please advise.

    I'm running an ADA head with high octane (9 premix, using Torco synthetic blend. I cut the first tank at 32:1 for the breakin procedure. I spent most of the day in the 3,000-5,000 rpm range and as high as 6,000 a couple of times.

    The first strange thing came on about 20 mins into my ride. The engine revs would drop to 4,000 rpm max and stay there. If I switched off the motor and back on (after 10 seconds or so) it was going great again. 5 minutes later, drop to 4,000 max. This continued throughout the day. I'm unsure of a limp mode, there were no warnings on the display all day but I did notice the ADA head runs a little hot (is this normal?). Only 5 seconds touch before it gets too hot. Cyls not as hot, they are about a 15 second touch before it gets too hot. The water temp sender from the stiger is hooked up, I am running a D-Plate but cannot locate the exhaust sender plug Is this limp mode, 4k rpm? I should add when I shut it off and start back up it runs excellent super responsive no bogging anywhere in the rev range.

    The other odd thing that happened was that at one point the engine seemed to be dieseling. It was stuck on 5,000rpm with no throttle - the throttle cable is perfect. This only happened once and I had to hiut the lanyard to shut it off.

    I ran the engine for about 1.5 hours today, I tested my comp and got 152/160/155 MAG-PTO. I also pulled the head to observe the wash, as you will see it is from one extreme to the other. I'm thinking 1 turn in on MAG, 0.5 turn in on CEN and 1 turn out on PTO on the highs. Since most of the day was spent around the 4k rpm range should I address the lows also?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    1200Jet's Avatar
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    Not sure if it has anything to do which your problem but your exhaust to stinger connector is mounted wrong, you need to rotate it inwards until the rubber piece is between the two tangs. If that makes sense!!

  3. #3
    Happily Self-Employed WFO's Avatar
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    there is no limp mode

    looks like you need to go back thru the fuel system

  4. #4
    urugol's Avatar
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    1200jet - thanks for picking that up looks like I got that wrong! Maybe that explains the engine running a little hot.....could it be related to the rpm issue I wonder as well. Fuel delivery is fine, like I mentioned it is very responsive and hits high rpm for 5-10 minutes then it drops to 4k rpm unless I stop and start the engine which led me to believe it was a cdi limited rpm. I mentioned that I can't trace the exhaust temp sensor from the CDI (supposed to be OB/O cable) so I thought the problem may be there but I have no warnings or buzzer which I assume would materialze should it be a problem. In terms of adjusters, any comments on the approach above?

  5. #5
    urugol's Avatar
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    Forgot to mention, I'm running BR8ES plugs with my comp numbers from 150-160 would I be better off running BR9ES plugs?

  6. #6
    1200Jet's Avatar
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    What octane fuel are you running?
    Did you pressure test the motor after the build?
    The BR9ES won't be any different for your issue but will probably be worth the change once its running well. They are slightly longer
    I haven't read any good things about the head your running and I would be thinking about changing it out for a stock machined or R&D if you can't find anything else wrong with the build.

    Looking at the difference in compression 152-160 I would think you have a leak somewhere.

  7. #7
    urugol's Avatar
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    Comp test would not show a leak, after all you are testing the ring seal in the combustion chamber only not the case. Engine has only been running for 1.5 hours so far so still need to complete the run in. I'm running 98 octane, highest I can get in Australia. I haven't heard anything bad about ADA heads so far. It does seem to run a little hot though which is interesting.

  8. #8
    A child of five would understand this. Go get one. pierowman's Avatar
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    Did you preform the leak down test? from what ive read when there are wierd throttle issues there is usually air leaking in some where. Common places are at the reeds and the crank.

  9. #9
    Every adventure comes to an end........ Not Today! wreckingball's Avatar
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    Quote Originally Posted by WFO View Post
    there is no limp mode

    looks like you need to go back thru the fuel system
    If you rebuilt the motor, don't skimp out now by not rebuilding your carbs... I'd even recomend sending them to OSB to get a little more performance out of them.

    Quote Originally Posted by pierowman View Post
    Did you preform the leak down test? from what ive read when there are wierd throttle issues there is usually air leaking in some where. Common places are at the reeds and the crank.
    This would be my guess as well. Do a leakdown with 2 or 3 pounds of air. Get a soapy water mix in a spray bottle and watch your gauge.

  10. #10
    urugol's Avatar
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    Quote Originally Posted by wreckingball View Post
    If you rebuilt the motor, don't skimp out now by not rebuilding your carbs... I'd even recomend sending them to OSB to get a little more performance out of them.



    This would be my guess as well. Do a leakdown with 2 or 3 pounds of air. Get a soapy water mix in a spray bottle and watch your gauge.
    Carbs have been rebuilt, all new mikuni original kits run through them. Forgot to mention I am running 44 blackjacks also. Leakdown test was done held 8 psi for a good 10 minutes during the rebuild phase. I put in new plugs and opened the high adjuster on the mag 2 turns out and have replaced the ADA head with the stock unit running at an even 125 lbs on each cyl. I'm thinking during run-in I will go with the stock head before going for big compression an make sure everything is spot on. I am also running riva gas valves, not sure if they would contribute to the 4,000 rpm limit I am seeing.

    Also thinking about it, even if I had a leak it shouldn't stop me from hitting above 4,000 rpm at full throttle since the mix is getting maximum fuel at the time.

    I did put in an aftermarket fuel filter also on the intake line, there could be a problem there as well

    The big one though, is that I have been running the wrong plugs for the first hour. Big mistake. I was using the polaris BPR8ES plugs instead of the BR8ES Yamaha spec I put the plugs in a tired night and have brand new of both as I have Polaris skis as well

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