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  1. #1
    cheatin' piston popper addicted's Avatar
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    need help distinguishing piston wash

    I didn't post this in the old school section because i wanted more visibility.

    It's a 99 npv 1200. 1mm over, ported jugs. running a riva cdi mod 1, 93 octane, 150 psi, 50:1 dominator. This is the wash after 13 gallons of mixed riding, but alot of WOT for the last few gallons. I have a feeling that the Dominator is making the wash less discernible than other oils? I got a tip to spray the crowns with some starting fluid to get a better read. pics are before and after. Also, I cleaned the domes before this tank, so this is all fresh wash. It revs out to 7150 ish. loads up at idle and is nowhere near perfect jetting. It was running the stock pilots, n&s and springs when I got it with 160 mains. Right now it has 115 pilots, 160 mains, 1.5 n&s and a gold spring. pops at 55ish. lower than that would dribble. Lows are 1 1/8 out and highs are 1/2 out after tuning for rpm's.main jets are alot bigger than most run with triples, but yet the wash looks lean???

    Please help!
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    Last edited by OsideBill; 08-16-2007 at 12:18 AM.


  2. #2
    Flying Scotsman's Avatar
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    Pics would say #1 is leaner than the other 2
    I think #1 is fine #2 and #3 are rich.
    I would like a little more wash on #1 but its probably right on.

    160 mains still seem huge to me are all the carb manifold gaskets good.

    Has anyone run 160 mains on this platform 44sbn carbs....

  3. #3
    cheatin' piston popper addicted's Avatar
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    Yup. gaskets, plumbing, everythunbg was inspected and replaced if needed before reassembly. 1 looks lean to me too, but I can't seem to tell. the pictures make the transition from carbon to aluminum alot clearer. in person it looks like the whole piston is covered in carbon spots.

    how did that other pic get in there? Mods, could you please delete the pic of the trunk of my jeep. I tried but don't have access.

  4. #4
    Flying Scotsman's Avatar
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    See what the experts have to say pics dont always capture the right colours but your wash looks good.

    Why such big jets porting still seem too big

  5. #5
    Moderator OsideBill's Avatar
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    OK Pic removed I am figuring this chit out little by little

  6. #6
    Moderator OsideBill's Avatar
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    Oh yeah the wash does not look too bad, how many hours?

  7. #7
    cheatin' piston popper addicted's Avatar
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    Thanks bill, you'll be the bestest babysitter in no time

    Hours? Whatever it takes to burn a complete, filled to the cap tank of gas. I cleaned the domes afetr the last ride. this wash is only from this 1 tank of gas.

  8. #8
    HopatcongGPR's Avatar
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    one cylinder is slightly leaner then the rest.

    what is squish set at? the darker colors on the squish band is telling me its in the .050 or greater range. get the squish down to .038-.042. you want the squish to slightly over lap or be damn close to the boundry layors at TDC.

    "Theoretical" ideal squish is lower the what I stated above...however...in our PWC we have to take some other factors into account and keep the squish slightly above theoretical "ideal".

    on my stroked 90mm motor i run between .035 and .038. i dont keep my boat clamped for long WOT runs...i am more "forgiving" then you may be....

    i would go up one full get size on the leaner cylinder AND go one 1/2 size jet on the other two. i dont like black carbon on the crown. i like a nice caramel color....plus..it will be getting cooler soon as well.
    Last edited by HopatcongGPR; 08-16-2007 at 12:21 PM.

  9. #9
    HopatcongGPR's Avatar
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    good article for you to read...

    http://www.geocities.com/rssarma/articles/dale_1.htm

    keep in mind what the author is working on....regarding a lower squish then what i state above.....but the theories and practices are basicly the same.

    and btw,,,dont spray staring fluid on the domes...its going to alter what you see....get a 200 dollar bore scope off ebay. it will be the best 200 you spend!
    Last edited by HopatcongGPR; 08-16-2007 at 09:17 AM.

  10. #10
    www.2-Stroke-Porting.com
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    Detonation Article

    Here is another article to go with Hop's.

    http://www.motorcycle.com/how-to/pri...ation-3420.htm

    To calculate the minimum squish clearance - I use Kevin Cameron's formula:
    0.0125 x Stroke in MM. Example - 1200 GPR ='s .0125 x 78 ='s 0.975 mm or 38.6 thou / 0.0386"

    You can run less than this provided: your ski does not come "unhooked", or you blow a belt on a sled, miss a shift on your bike.

    To answer your question - it looks like you could be lean in your mid-range circuit. I agree with Hop - I don't like to see black carbon on top and if you see it under the piston crown - it is a killer.

    Enjoy the read.

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