The Crying Shame of Jetting

Discussion in 'Trials' started by motobene, Apr 22, 2017.

  1. KrAzyOSUcOwBoY

    KrAzyOSUcOwBoY kRaZy

    Joined:
    Mar 29, 2006
    Oddometer:
    163
    Location:
    SW Okla
    Just to follow up on my 26mm OKO install. The back ground on this 2014 GG 225 is here if you are interested. The modifications are not especially performance related as the bike runs well as jetted with the Dellorto, I was hoping to improve the bike's starting demeanor. I believe the the "slap" kick required to spin the engine quickly enough to create a robust spark is still part of the cold start difficulty. But easier and more reliable hot starting would be a valuable improvement as well. So here are the steps and my results. To remove the Dellorto and replace with the OKO/PWK look alike is about as plug and play as it gets. I used a red Jitse adapter on the intake side and no modification was necessary on the filter side. We also ordered the angled top for the throttle cable. This created a bit of an issue with the cable length, easily solved with a 1" adapter. Jetting as supplied from Roger at USA-OKO was 120 main, 50 pilot, JJH needle 2nd clip position. I unpacked the OKO and removed the float bowl to check the float ht and the jet sizes. Removed the carb top to check the clip position, which was 2nd down and is the best position so far (started with the middle position,more on that later). Next was to silicone the Jitse adapter to the engine side of the carb. Fit with the adapter was excellent. Test #1 next....
  2. KrAzyOSUcOwBoY

    KrAzyOSUcOwBoY kRaZy

    Joined:
    Mar 29, 2006
    Oddometer:
    163
    Location:
    SW Okla
    So, Test #1 after initial install with the jetting set like this: 120 main, 50 pilot, JJH center clip of 5, A/S 1 turn out. Started as normal, requires 2 swift kicks. Set the A/S to best idle, 1 turn and rode around yard, sort of. Ran perfect to 1/4 throttle then went flat (no further acceleration) . Test #2. OK, set the needle one clip leaner, starts fine, runs to 1/2 throttle, goes flat. Must be rich, to much main jet, order additional jets. My first guess was 115 main. Remove carb, wonder what that rattle is? OOps, main jet had fallen out of the needle jet. Explains runs fine goes flat. Put in 115 main, tighten adequately, remove float bowl, switch to 52 pilot ('bene's suggestion), reset A/S to best idle, 1 1/2 out. Test #3. Cold start requires typical swift kick, second kick start. Runs great at all throttle settings, idle to full. Hot starts are slightly less finicky, the OKO like a hand full (1/2 or more) of throttle and a reasonably quick kick. the Dellorto was throttle closed and maybe the enrichener on with a swift kick. We'll ride these setting for a while to get a more thorough evaluation. I think I'm going to like it or something close, don't want my jetting to be a "crying shame."
    Brewtus and jonnyc21 like this.
  3. motobene

    motobene Motoing for 49 years Supporter

    Joined:
    Mar 9, 2013
    Oddometer:
    6,244
    Location:
    Wichita Mountains SW Oklahoma
    Thanks for the update. Main jet fell out. That explains how the power could fall on its face. That result out of the starting gate would have freaked me out!

    You have the additional challenge of the 225cc kit, which is made from a modified 250 cylinder and piston with the cylinder height reduced. The piston dome doesn't quite make it to the bottom of the transfer ports at BDC. It's close enough for a great running bike and with the largest available flywheel weight is not hyper active from the smaller 125 flywheel. But like jetting the Dell'Orto with the kit, some patient iterating will likely be required over the coming months.
    KrAzyOSUcOwBoY likes this.
  4. KrAzyOSUcOwBoY

    KrAzyOSUcOwBoY kRaZy

    Joined:
    Mar 29, 2006
    Oddometer:
    163
    Location:
    SW Okla
    Boysen carbon techs are still in there. Heavy fw weight. Problem with timing retard, Bene will have to explain that one. Starting is very sensitive to technique, but less so hot with the carb swap.
    Solarflares likes this.
  5. Solarflares

    Solarflares Been here awhile

    Joined:
    Feb 9, 2019
    Oddometer:
    383
    Location:
    Norfolk , UK
    With that idle jet - I should think it starts itself when the wind blows!
    lineaway likes this.
  6. DyrWolf

    DyrWolf Long timer Supporter

    Joined:
    Jan 21, 2012
    Oddometer:
    2,024
    Location:
    RICHMOND VA
    My TLR with OKO