1. Some members were not receiving emails sent from XJbikes.com. For example: "Forgot your password?" function to reset your password would not send email to some members. I believe this has been resolved now. Please use "Contact Us" form (see page footer link) if you still have email issues. SnoSheriff

    Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

Idle problem Yamaha 80

Discussion in 'Other Motorcycles' started by tabaka45, Jan 2, 2017.

  1. tabaka45

    tabaka45 Well-Known Member

    Messages:
    2,397
    Likes Received:
    513
    Trophy Points:
    113
    Location:
    Brunswick, Georgia
    I have cleaned the carb, replacing the jets and wet setting the float. While it starts easily it wants to idle at irregular rims. It feels like the throttle is hanging up but I have verified that the cable is free and the slide snaps back firmly. I have also installed new intake gaskets and haven't found any air leaks, but I am going to recheck that. Before cleaning the carb it would over flow gas from time to time but not since cleaning and setting the float. This is a Makuni carb and while the float needle can be replaced thneedle seat is machined into the carb body and can't be replaced. I've rebuilt my Xbox carbs with no problems, but this has me stumped. Any ideas?
     
    tabaka45, Jan 2, 2017
    #1
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,755
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    I wouldn't jump right to suspecting the neeedle seat, but is can be polished with jewler's rouge and a golf tee.
    The Coulotune should fit in that spark plug hole. See what the idle color looks like. Does it jump around?
     
    k-moe, Jan 2, 2017
    #2
  3. tabaka45

    tabaka45 Well-Known Member

    Messages:
    2,397
    Likes Received:
    513
    Trophy Points:
    113
    Location:
    Brunswick, Georgia
    The needle seat is just machined into the aluminum and I would be afraid to try to polish it. I've looked at it and it appears to be fine. My colortune didn't come with an adaptor that small--any idea where to get one? The idle doesn't jump around. It just doesn't return to idle once revved up. Acts like a binding throttle cable or something to do with the throttle or slide. The cable is like new and I've lubricated it. The slide returns with a snap so it appears to be operating ok. If kI have it at normal idle and rev it a little it will idle high--I'm guessing 2000 plus or minus. It might stay there 15 seconds to a minute and then gradually return to idle. If it is in gear and moving then hitting the brake will return it to normal. Just strange.
     
    tabaka45, Jan 2, 2017
    #3
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,755
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    It was polished at the Mikuni factory to begin with. If it looks fine then it probably is, but touching it up won't hurt. That is the only way to service those seats, short of machining them to take brass seats.

    As for the idle....hmm.....ya.....a thinker.

    Does it matter if you remove the throttle cable from the throttle tube? If the throttle tube were binding...
     
    k-moe, Jan 2, 2017
    #4
  5. Toomanybikes

    Toomanybikes Well-Known Member

    Messages:
    2,836
    Likes Received:
    815
    Trophy Points:
    113
    Location:
    Tsawwassen bc
    80cc 2 or 4 stroke. 2 stroke , crank seals or reed valve may be the issue.
     
    Toomanybikes, Jan 2, 2017
    #5
    k-moe likes this.
  6. tabaka45

    tabaka45 Well-Known Member

    Messages:
    2,397
    Likes Received:
    513
    Trophy Points:
    113
    Location:
    Brunswick, Georgia
    2005 80cc 4 stroke

    I disconnected the cable from the trottle but not at the carb. the cable screws into the top of the carb so that it can connect directly to the slide. Even with the cable disconnected from the throttle the problem continues. The slide is free and snaps closed. But it sure acts like something is binding and finally closing maybe due to vibration. Strange.
     
    tabaka45, Jan 2, 2017
    #6
  7. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,755
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    If it's a PW than I'd start thinking crank seals or reeds like Mr. Bikes says.
     
    k-moe, Jan 2, 2017
    #7
  8. tabaka45

    tabaka45 Well-Known Member

    Messages:
    2,397
    Likes Received:
    513
    Trophy Points:
    113
    Location:
    Brunswick, Georgia
    It's a 4 stroke and the valves have been adjusted and are within specs.
     
    tabaka45, Jan 3, 2017
    #8

Share This Page