1. 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.

1982 Yamaha XJ750 Seca won’t idle

Discussion in 'XJ Technical Chat' started by Luca C, Jan 4, 2022.

  1. Luca C

    Luca C New Member

    Messages:
    1
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    Florida
    Hey guys, very new to this but looking for help…

    I bought an 82 xj750 seca as a project motorcycle: she didn’t run when I bought her. I’ve rebuilt the entirety of the carburettors because they were a mess and completely replaced the whole spark plug and assembly because I believe it had intermittent spark.

    no matter what I do I just can’t get the motorcycle to idle. The engine churns a little with a nice deep grumble as I try to start it up but just won’t idle on it’s own. As far as I’m concerned, the only other thing I need to do with the carbs is sync them (but obviously cannot take that step without the motorcycle in running condition. I’m yet to adjust the floats however, could that be the reason she won’t idle on her own?
    Any help/suggestions are greatly appreciated!
     
  2. dkavanagh

    dkavanagh Well-Known Member Premium Member

    Messages:
    1,301
    Likes Received:
    570
    Trophy Points:
    113
    Location:
    Rochester, NY
  3. Huntchuks

    Huntchuks Well-Known Member

    Messages:
    951
    Likes Received:
    395
    Trophy Points:
    63
    Location:
    East Rochester, NY
    Jetfixer likes this.
  4. Jetfixer

    Jetfixer Well-Known Member

    Messages:
    3,173
    Likes Received:
    1,485
    Trophy Points:
    113
    Location:
    Nothern Indiana
    When you say you rebuilt carbs ( a rebuild in a can will not cut it ) breaking the rack and replacing all the butterfly seals is only way to do a proper " rebuild". To get to the seals the butterfly plate has to be removed and shaft pulled out of carb body , remove idle mixture screw and the rubber O ring then the carb body can be soaked . Once carbs are reassembled and the carb bodies put back onto the rails , take two number 20 drill bits place one under number three butterfly, slide another drill bit under number one butterfly plate adjust the synch screw till there is a slight drag pulling on bit , once satisfied move to number two , and finally number four , turn idle screw in slightly till number three has a slight drag . The idle mixture screws turn all the way in and back out two in a half turns . I normally set float height at 17.5mm I have had good luck when checked wet set this way . After putting carbs back on ensure carbs are full by opening float bowl screw till a little fuel dribbles out . Before trying to start make sure battery is fully charged , then try to with full choke . Your idle should be around 1100 rpm . I should add make sure your intake boots are in good shape and you have good caps on the bleed nipples . If the boots are weather cracked a good coat of black RTV can often do wonders to help slight vacuum leaks . Sorry to overload with info , but I have done many bikes and my two secas run perfect . Cheers
     

    Attached Files:

    Noahsxj and Franz like this.
  5. Huntchuks

    Huntchuks Well-Known Member

    Messages:
    951
    Likes Received:
    395
    Trophy Points:
    63
    Location:
    East Rochester, NY
    Jetfixer, I like the VW bug. I had a yellow one like it in the 70's. Always liked driving the Beetle, so fun.
     
  6. Timbox

    Timbox Well-Known Member

    Messages:
    2,278
    Likes Received:
    748
    Trophy Points:
    113
    Location:
    Wisconsin, Tomah
    If this is your first time working with these types of carbs, you can almost bet you missed cleaning something. If it will not idle then for sure the carbs need to come off again. Like stated by above..read up on those links. They are great threads and have supper directions with pics.

    To be honest, I pulled my carbs off my first XJ project bike six times. Take your time with them as they are one of the most important components of the bike to make it run right.
     
    Jetfixer and Franz like this.
  7. Noahsxj

    Noahsxj Active Member

    Messages:
    200
    Likes Received:
    105
    Trophy Points:
    43
    Location:
    SW Missouri
    @Jetfixer nice vw
    Just helped my father in law find a wire gremlin on his 71 fastback over Christmas , and he’s pooling parts together right now for a “family rebuild” on a 73 squareback haha
     
    Jetfixer likes this.
  8. PJC750

    PJC750 Member

    Messages:
    127
    Likes Received:
    12
    Trophy Points:
    18
    Location:
    Northeast
    Whats the spec on the idle adjustment screw?
     

Share This Page