The pursuit for a brown sparkplug

  • DTR Member

    0_1523479617203_20180411_170225.jpg 0_1523479621613_20180411_170218.jpg

    Alright, trying to set up this Athena kit. Currently running 280 main jet and this is what the sparkplug looks like after ~250km. Looks pretty good huh? Sadly, the bike won´t rev fully, no power beyond 3/4 throttle. Running lumpy, strange. Wouldn´t say bogging but something is certainly not right down there. The question is, should I go down to 270 or up to 290? What´s your opinion? Personally, I´d want to try a smaller since almost everyone with the kit runs 270. However, since I´ve not pushed the bike that much during break-in, and the sparkplug isn´t completely black from a very rich mixture, I´d say I might as well try 290. A safer bet for sure.
    And no Calum the pv is not pinned in the closed position 😉

  • Administrator

    It's not really appropriate to be judging the fueling on break in, you need to put that engine under load and perform a plug chop to really understand how the fueling is doing.

    Once it's bedded in, perform a plug chop and report back what the plug is doing then.

    I'd say that plug looks a tad lean to me.

    Easiest way to tell is to restrict the air flow into the bike, if it performs better then you know you need to increase the fueling.

  • This is mine (no kit though), a bit of deposits from excess oil, but otherwise tan as Hasselhoff!!

  • DTR Member

    Wow! I'm impressed! I'm now running 290 main jet. Can't feel much difference. My issue is, it does not pull after 3/4 throttle. The revs go up, exhaust getting louder, I brace for the real powerband but then nothing.. Dropping to 3/4 and she goes! But there is definitely power left to scavenge. My next alternative is to try a 270 main jet. And yes I've tried the choke, no results.
    Should I really be giving the piston, cylinder full throttle? I'm closing in to 300km.. Shouldn't be an issue right?

  • DTR Member

    The amount of response is overwhelming


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