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  1. #1

    Smile GP1200 sparkplugs update!!!!!!!

    Hi Everyone,

    I don't post here often but here is a tip that i think everyone who owns a yamaha 2 stroke ski should have, specifically the gp1200 but any non powervalve yamaha 2 stroke waverunner could potentially use this.

    I've never been happy with the lumpy shakey idle my gp1200 has had, some of you know this. And it's been known that the yamaha non powervalve 3 cylinders are "shakers" at idle.

    well I think its cured!

    Everyone knows that indexing your sparkplugs improve the top end slightly and make a slighly smoother idle, but not by much.

    I noticed this on my blaster and more recently my gp1200. I was using my GUNSON'S COLORTUNE ( http://www.autoexpertproducts.com/colortune-14mm.htm ) to set the mid range mixtures and noticed that the colortune glass plug wouldnt fire very often, asif the exhaust gasses were trapped in it preventing ignition. Thats exactly what WAS happening. The loop scavange was not able to clean away all the burned gasses and the plug would spark, but not ignite the new air fuel mixture.

    I got to thinking and wondered if the same thing was happening with the factory plugs, and hence the crappy idle with my 760 converted blaster, and the same thing with my gp1200. (they both suffer from crappy shakey unstable idles, and are both inherently the same design engine, just plus or minus a cylinder.)

    Well I do remember seeing some marine plugs that used a surface discharge ring ground electrode, and had no internal volume for exhaust gasses to hide in. Specifically I'm talking about the BUHW sparkplug from NGK... champion makes a similar offering, i beleive the L77 or L78 or something along those lines.
    The heatrange while not listed i researched does fall into the range needed. It has no crap sticking out of it to cause pre-ignition or detonation, and has no internal volume for exhaust gasses to hide in. ON TOP OF THAT, Since there is no ground electrode to block intake charge from sweeping the plug clean!!

    I installed in the middle of the week but did not have a chance to test run the machine until yesterday evening.

    LOL at first i had completely forgotten i had changed the new NGK BR8ES plugs to these, NGK BUHW plugs... I started it up idled it out through the no wake all the while itching to take advantage of the weather.... (6pm and the sunset was coming fast). I do remember turning around and looking at the exhaust.... usually half way out of the nowake zone id smell my exhaust and it would irritate me... but i noticed nothing but a little smoke... i thought nothing of it because of my urge to get the hell out there and enjoy what little time i had.

    I get out there run around and I did not notice any speed lost or anything... again I had forgotten about the plug change.

    I come back in... I hit the no wake zone and idle the rest of the way in to the ramp... This is where I always used to notice how horrible the idle was. But I didnt take heed of it until half way through the no wake zone I realized the idle was superbly smooth, clean and crisp.

    I got back in and was not sure if i had just test fitted the plugs and put the originals back in, or if i left the new surface discharge plugs in... I got home, popped the seat and low and behold, NGK BUHW's on all three cylinders!

    At 2.50 to 4.50 a pop, I really suggest someone else try them... I was amazed at the idle performance, and that it was an all win modification. I pulled the plugs and all three are burning properly and very easy to identify the mixture ratio.
    These plugs are also used by a large variety of marine 2 stroke engines... probably for the very same reason they improved my idle so much, i know they are used on mariner and mercury engines.

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    Last edited by the_natrix; 08-28-2010 at 11:02 AM. Reason: added info again


  2. #2
    found your post on the plugs that is weird my Mercury on the bench now ran the same plugs I will give them a shot in the gp1200 because I end up doing a lot of no wake crap on Lake St. Claire thanks again

  3. #3
    zx11rider's Avatar
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    My merc 200 outboard used those plugs and it was a 2-stroke.

  4. #4

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    Very interesting post!

    i would be intrested in wether you lost (or gained) any rpms. This would be the biggest selling point.

  5. #5
    fatrat's Avatar
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    this might be a little over the top for this thread but if you were trying to add in several degrees of timing wouldn't it be hard to read using these plugs? there isn't a strap to be able to see the timing mark made on it.
    My brothers boat uses this style of plug and for some reason i am sure they are better in some ways than those conventional style plugs 99% of us are using, in marine applications.

  6. #6
    while i am after performance, this was not directed for performance modifications it was directed basically for a quality improvement. The idle quality and fuel economy has both been improved now on my gp1200, and im quite pleased about it.

    I assume, if someone were after performance and needed to utilize the sparkplugs for traditional reading purposes, then it would be smart to continue using the slightly cheaper regular br8es plugs. Once tuning was completed then it might be wise to try these out and get the benefits of the reduced misfires and smoother low speed performance.

    I have no reliable tach to use so I cannot come back with rpm numbers, and I will be stuck in japan for the next 3 months come tuesday... But i feel at 12 bux its worth it for someone who has said equipment to try them out.

    Like i said, my idle quality has greatly improved, and my fuel economy has improved. That's 2 stones in the bucket that i even feel is worth a slight hit in performance if these plugs even have a drop in performance. I feel my machine runs and responds the same as it did with traditional plugs.

  7. #7
    fatrat's Avatar
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    where did u find those plugs at for 2.50 to 4.50 in price????

  8. #8
    txgp1300r's Avatar
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    FYI....great post...... I have been side gapping my plugs for years.....its a solid 20 rpm's. I may try some surface gap plugs just out of curiosity.

  9. #9
    agsbill's Avatar
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    I got three in Gainesville, Ga.....O'Rilleys...for $1.99 each......

    I have a PV engine and didn't see that part of the original post....

    The NGK BUHW don't have as much thread as the BR8ES-11...and therefore don't reach as far into the cylinder as the dash 11s

    I am going back to the store and see if they have anything like BUHW but with the same thread as the BR8ES-11..

    I am impressed so far...starts quickly without choking!

    Bill

  10. #10
    Bill here`s the spec on the -11`s

    http://www.sparkplugs.com/more_info.asp?AAIA=&pid=3720

    and the BUHW

    http://www.sparkplugs.com/more_info.asp?AAIA=&pid=2634


    these are 1/2 reach, they are indeed to short...

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