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  1. #1
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    2016 FX SVHO - cold engine stalling . . . SOLVED!

    This is going to be a long post, as there is some history, and I don't want to skip any details, as they are all important.

    I bought my 2016 fx svho with about 15 hours on it. It has always had problems stalling when cold. These are the situations that it would stall.


    1. start, run for a few seconds then stall.
    2. start, idle, give it some gas, and it would stall when the throttle is released
    3. start, idle, stall when going between forward and reverse and back (typical dock maneuvering)


    My solution was to pull away from the dock as soon as I started it and give it some gas till it warmed up a little, then it would run fine. Of course, around the dock, this wasn't ideal. New plugs, lots of new gas, high octane non-ethanol gas, it really didn't matter, when it was cold, it did not want to stay lit. Some said that a tune would solve this problem. I was doing a few mods, and had the ecu flashed with a Dean's Team tune (great tune btw). That didn't solve the stalling problem. I resolved to live with it.


    About 16 months after I bought the ski, at about 80 hours, discovered water in the oil which was a result of a cracked head. Ordered a new head from Yamaha, swapped valves over, installed it, re-shimmed it put everything back together. It wasn't running great, but I thought maybe the valve clearance needed to be re-adjusted. Took it out a couple more times for a total of about 2 hours, and it was still running a little rough. Of course, the stalling while cold was still there.


    The next time I went to start it, it wouldn't start at all. Figured this was a good time to re-check the valves. Started by taking out the plugs, and discovered that one of the plugs actually had the gap close up. This same plug co-incidentally had an ignition coil that was difficult to put on and take off...like it was sitting a little higher than the other ones when it was first installed, and it seemed like the boot was inserted far deeper onto the spark plug which made it difficult to remove.


    When comparing the plugs, I also noticed that the crush washer on this faulty plug did not look like it had been seated. I went back to check how many turns it took to seat each plug, and the faulty plug had about half the turns that the others did before it was torqued, and again, the washer didn't seat. I thought it was odd, but perhaps the threads hadn't been fully tapped. My good friend who had been helping me then proceeded to use a new plug to slowly tap/clean the spark plug hole an 1/8th turn at a time, and he was able to slowly advance it till the plug was fully seated. After that we installed all new plugs, and this time, the ignition coil was easy to install.


    It started right up, and ran nicely in the shop, but then it always did. It only ever stalled when it was in the water.


    The next time out, I was prepared to do my usual routine of giving the ski some revs right after starting, but noticed that the engine started right up, and idled very nicely. Didn't warm it up, and pulled away from the dock, surprised that it didn't stall. Transitioned between forward and reverse a few times, never stalling. At this point, I was amazed and happy, as this was always an issue that I had with this ski that I had decided I would have to live with. Since then, the ski starts perfectly, idles perfectly, can go between F and R repeatedly and has never stalled again.


    There was a few threads a while back about guys who had skis that stalled when cold. I would suggest that this might be the issue, that a spark plug is not fully seated, and is not in the perfect position in the head. It's fine when warm, but when cold, it just doesn't run properly and would stall. I was surprised that there was an issue with the threads of a spark plug hole in a brand new head, but I guess anything can happen.


    Sorry for the long post, but for anyone that has a stalling issue, and has given up trying to figure it out, give this a try and see if it might be the problem.


    I'm sure that using the spark plug to clean out the threads in the head was probably a dumb thing to do, but it was one of those F**K it moments. It turned out ok for me, but as usual, use caution when working on your own ski. I also realize that this is a new head, but perhaps the spark plug on the original head also wasn't seated all the way. Unfortunately, I threw the head out before I figured this out. Might also have been the valve adjustment on the original head, but the factory has much more range of shims to choose from than we can get, so they should be able to get the valves much closer to the optimal setting than we can (0.01 or 0.02 mm increments vs 0.05 mm increments that are available to us)

    Good luck!


  2. #2
    Great post-thank you!!!

  3. #3
    MSX 150 guy lives on Mr. GP1800's Avatar
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    Quote Originally Posted by seabrook View Post
    Great post-thank you!!!

    And he he didn’t even have to sue Yamaha

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