I’m at a loss

Discussion in 'Carburetor' started by Brandonp2287, Mar 22, 2020.

  1. Brandonp2287

    Brandonp2287 Member

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    So. 04 blaster. Fresh rebuild, bottom up. Wiseco crank and piton. Niche jug And head. Hot rods and All Balls bearing everywhere else. So when I got the bike it was stock everywhere. I put a FMF gold fatty and power core 2 silencer on it. Ran great with no tuning or jetting. Since I’ve done this rebuild, I haven’t been able to get it to run right. It spits and sputters and just simply refuses to clear up. It doesn’t have the torque it should. Somethings just not right. Compression is ~120. Leak down test showed a drop of a little less than 2psi in about 40minutes. So I went to the carb thinking that was my issue. Stock it was 32.5 pilot and 230 main. Since the build the fuel/air mixture screw doesn’t do anything. So I ordered the Vitos blue needle carb kit. Blue needle stock pilot and main. No good. I tried every pilot from 25-32.5 to make the air screw have some effect. I’ve moved the needle clip, no good. I’ve gone up to a 250 main, no good. Plug says I’m running rich though. All black and wet. I live 15 miles from the beach so next to no elevation. Is it possible the main jet is so far off that the air/screw mixture screw can’t overcome it?
     
  2. Slydog

    Slydog Member

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    With the fmf you should probably be in the 270-300 range on main jetting.stock pilot jet. Did you clean carb good.float hight is set correctly.all holes in carb are clean .see daylight through jets .air filter is clean.reeds were sealing good? Or exhaust restriction
    Check float hieght first
     
  3. Slydog

    Slydog Member

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    Niche is that a Chinese cylinder kit?
     
  4. Brandonp2287

    Brandonp2287 Member

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    Yes it is. Fingers crossed on it.
     
  5. Brandonp2287

    Brandonp2287 Member

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    It’s all clean inside and out. Actually had an issue of it dripping gas due to incorrect float recently. Corrected that. Clean filter, new vitos reeds. Going to clean carb again since it’s already off the bike from the leak down test. And will check float height again. Is it possible the main is so far off it’s throwing everything else outta whack?
     
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  6. Slydog

    Slydog Member

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    What happened to oem blaster cylinder?
     
  7. Slydog

    Slydog Member

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    If you were leaking gas. Maybe a new needle valve.you will not be able to get jetting right till that is fixed. The 230 main that you ran with the fmf is probably why you did this rebuild.fmf pipes requires bigger main jetting than the stock exhaust.230 is way to lean
     
  8. Slydog

    Slydog Member

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    Toes to:rolleyes:
     
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  9. Brandonp2287

    Brandonp2287 Member

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    No joke
     
  10. Brandonp2287

    Brandonp2287 Member

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    Failed about two years before I got the bike. Guy rebuilt motor.
     
  11. Brandonp2287

    Brandonp2287 Member

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    I’ll


    I will order a needle valve tonight to be sure. And you’re probably right. The first piston and ring kit I did had a wrist pin bearing failure. Which crashed the bottom end. So I did a full top to bottom this time. And worried to death I’m gonna tank this build.
     
  12. Awk08

    Awk08 Administrator Staff Member Technician

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    No, No it did not.

    Sly has told you 3 times above that a 230 main is too lean and that you need a 270-300 main jet for an FMF exhaust, but your last comment is "I'll buy a needle valve" :eek:

    buy 270 thru 300 main jets, start large and plug chop down to get the AFR correct
    https://www.blasterforum.com/threads/how-to-plug-chop.53237/


    let me tell you one more time
    3tnsj5.jpg
     
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  13. Slydog

    Slydog Member

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  14. Slydog

    Slydog Member

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    That's a good one
     
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  15. Brandonp2287

    Brandonp2287 Member

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    Nice little gif thing there awk. I already have the main jet kit. Let me say it again. I ALREADY HAVE THE JET KIT. That’s what the Vitos blue needle carb kit is. And yes. Yes it did run good. I’m not saying it wasn’t too lean. Not at all. But it ran like a scalded dog. I’m not saying it didn’t crash the top end. But it definitely ran better then than it does now. My question is not what size jet to run(270-300!!!!!!!!!!!!!!!!!!! As I’ve been told several times now as you thought I was too ignorant to read it the first time). My question awk was if the jet could be so far off that it was causing my air/fuel screw to not have any effect on the motor, NOT what size main to run. Because is that not where I’m supposed to start tuning? Float height then start with the air screw to get the pilot right, then do the main. Right? I’m trying to work in order as I’m supposed to, but if the air screw doesn’t have any effect on the engine idle then that says my pilot jets off correct? And AWK yes I said I’ll buy a needle valve tonight because I was taking sly’s advice on the leaking gas, not because I’m ignoring his statements on mains. That’s because I ALREADY HAVE the jet kit. One more time in case you missed it, I already have the jet kit!!!!!
     
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  16. Awk08

    Awk08 Administrator Staff Member Technician

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    LOL
    I never saw you say you had a jet kit, maybe I overlooked it ?
    If it was there, I wouldn't have seen Sly mention the main jetting 3 times ?

    But, there in lies your problem, the blue needle in the vitos kit is a notorious jetting nightmare, proven time and time again on here.
    I know of only one member who had success with it, and that's because he's running the vitos fat bastard pipe it was obviously developed for, then shoved in them kits and peddled to everyone, yet it only works for their pipe.

    you do indeed have the jetting sequence correct, start at the bottom and work up.
    pitch that blue needle, put the stock needle back in, and carry on
    I'll hit ya with another nifty meme/gif when you get it right :D
     
  17. Brandonp2287

    Brandonp2287 Member

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    Pitch blue needle got it. Next question. While starting at the bottom, should I already have the higher main installed?(I guess that should been one of my very first questions). But live and learn. And while I may not have specifically said jet kit, I did say I had the blue needle kit. Sorry for any confusion. Lookin forward to the gif. And thanks for the help guys. I’ll let ya know how it pans out.
     
  18. Awk08

    Awk08 Administrator Staff Member Technician

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    The main jet has zero effect on tuning any of the below circuits, as it only comes into effect after 3/4 throttle opening.
    it should be reacting to airscrew turns, if you're allowing 10-20 seconds between turns to allow the engine to catch up to the new AFR ?

    I've tuned quite a few stock carbs, in various states of tune and pipes, from stock, to FMF's, to ported with right bend pipes.
    every one of them wanted the stock, genuine mikuni, 32.5 pilot, and the airscrew tuned to highest idle between .5 and 2 turns out,
    the stock needle on the middle clip setting.
    the only instance I can remember anyone needing to lower the clip/raise the needle, to richen the needle circuit, is for the DMC pipe.

    but, I am at 1800' elevation, I see you mentioned sea level, and that does indeed play a big role in tuning,
    I don't recall any members at sea level mentioning needing a richer pilot, or a lower needle clip setting.
    there is normally enough airscrew tuning to adjust for most elevations in the US, using the stock 32.5 pilot in the stock carb
    this can be checked here ....
    https://www.blasterforum.com/threads/what-jets-are-you-using.28981/
    and
    https://www.blasterforum.com/threads/jetting-numbers-the-solution.17259/


    I'd start over and double check everything starting with float height, that you are using a genuine mikuni 32.5 pilot, and take each tuning circuit one at a time .... set the float, get the airscrew/pilot tuned for highest idle, allowing time for the engine to catch up to the new AFR after each slight turn of the airscrew, to find highest idle of the airscrew, the stock needle on middle clip, and main jetting plug chops last.


    one last thing I can think of for now, are you running the stock oil injection ? or mixing at 32:1 ?
    and if mixing, is the brass oil injection port on the carb capped off ?
     
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  19. Brandonp2287

    Brandonp2287 Member

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    Mixing at 32:1. And I guess the port is not capped off, I haven’t called it and there are no caps on it anywhere. Guess I might wanna do that huh? There’s never been any caps on it‍♂️‍♂️. And I’m about to dread it apart and start over in the carb, but gonna go ahead and put the 300 main in. And great links, I’ll definitely be using them
     
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  20. Slydog

    Slydog Member

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    There you go .there is a sequence to tuning.
     
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