Cuts out at 3500 rpm

Discussion in 'Harley Davidson Extreme Modification' started by lzmj3s, Dec 30, 2008.

  1. lzmj3s

    lzmj3s Member

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    My Custom bike has 88 Rev Tech with CV carb. It cuts out at 3500rpm but then picks up and continues to rev. Put it on Dyno to verify and tech confirmed. He seems to be very knowledgable and said he thought the 40mm carb was too small and probably has an oversized main jet to compensate. Cruising reading is 13.7 but cranking the throttle full open causes plugs to foul because of too much fuel to air ratio. He suggested not putting any money into the CV and ditching it for a Mikuni 45mm carb. Is it possible to make the CV work with a smaller main jet or spend the bucks for a Mikuni? I'm not that interested in Max speed but I want the bike to run good at all RPM's. Is it possible there is a different diagnosis or is he right on.
     

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  2. glider

    glider Veteran Member

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    Is the 88 pretty much stock or is it worked?

    The CV40 is a good carb and unless you are pushing some serious numbers in HP, it should be enough to feed that motor. Before going to a Mik, I would verify the jetting size in the carb on the motor now and possible rejet it. More than likely you may have something like a 200+ in the high speed from what you say or a slide that was drilled causing the problem. Also check the height on the main jet needle in the slide and see if it is shimmed up high in the holder which would also cause a very rich area at about that RPM.
     
    Last edited: Dec 30, 2008
  3. lzmj3s

    lzmj3s Member

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    Main jet is a 190 and pilot jet is a 48. Changed the pilot to a 46 and helped a lot, but it still cuts out. Needle is set in middle slot.
     
  4. glider

    glider Veteran Member

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    This is a stock 88 ?????

    190 is BIG. 46 should be good on the bottom end. I would drop to about 180 and check to see if the slide is drilled too. May have to check it with numbered drills to compare to a stock slide as far as the hole size. When you drill the slide and also if the diaphragm spring was replaced with a shorter one or cut the stock one a coil or two like some do, the slide raises to fast and can cause problems like you are having. Couple that with the 190 and you have an overly rich situation at higher throttle settings.
     
  5. glider

    glider Veteran Member

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    I agree (My Custom bike has 88 Rev Tech with CV carb) but sometimes posters forget to mention it STARTED as an 88 but then added this that and the other thing and add it later on. Nothing in....nothing out!
     
  6. lzmj3s

    lzmj3s Member

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    Everyone I talked to said these jets were too big for a 88 so I called Custom Chrome and gave them my serial number and they said it is actually a 100" GenII. Number is 585060XXXX. This might change everything. I had a 180 in my hand but decided not to change it but rather wait and see what the 46 pilot did. Do you think I should try a 185 since this is actually 100"? Don't know what changes have been made to motor. Tried to call previous owner but since he lost the bike in a divorce, He wasn't very helpful. He actually suggested I could kiss his ---!
     
  7. glider

    glider Veteran Member

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    Well there ya go now, just as I thought.
    The 185 would lean it out and may help but the issue then is the spring on the diaphragm and the vacuum hole too that should be checked. Some people thing that by pouring the fuel in that it goes faster and that's where the problem starts.
     
  8. glider

    glider Veteran Member

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    Excellent point Hob....My head hurts:small3d035:
     
  9. lzmj3s

    lzmj3s Member

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    Spring looks to be intact but I guess I Don't know about vacumm hole or what type of jet. I'll have to look at it when I put in the 185. By the way, previous owner did build this bike, but it was for his wife. That's why she took it! Let that be a lesson, never build a bike for your wife!
     
  10. R. Lewis

    R. Lewis Senior Member Retired Moderators

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    gotta ? for ya ---- you don't have the bike AND wife do ya!!??? hahaha!!!! If you do maybe thats why the prev. owner told you to "pucker-up"!!!:D