1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Help 1989 GSXR 250R - carb tune?

Discussion in 'Suzuki 250cc In-line 4's' started by John McLeod, Apr 17, 2019 at 8:24 AM.

  1. John McLeod

    John McLeod Member

    Messages:
    5
    Likes Received:
    4
    Trophy Points:
    13
    Joined:
    Mar 26, 2019
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    1989 GSXR 250R
    Hi guys/gals, I have a bit of a problem that I’m hoping I can get some help with


    I have recently bought a 1989 GSXR 250R GJ73a and I think it is running too rich. It will start from cold with no choke and idle great with a very responsive throttle, but won’t idle when warm – it will bog down and die unless I give it a bit of throttle. For the life of me I can’t see any air/fuel mixture screws on the carbs. There is only the one idle adjust screw. I assume they are aftermarket carbs – they have “Mikuni Corp” and “made in Japan” on them but no other markings or adjustment screws that I can see or easily access. Are they in a hidden spot?

    I did take the carbs apart to clean when I bought it and they were pretty clean and the jets weren’t blocked. Someone has drilled about 10-15 holes in the top of the airbox, and the jets are 47.5 and 105 on the outer carbs and 110 and 47.5 on the inner two, with all pilot jets as 12.5.

    I checked the plugs and all have a spark but are very black and carboned up. I also found that one cylinder wasn’t running so I am going to check that carb float bowl to see if it has fuel in it, and if so then I’ll take the valve cover off and check for stuck/sticky valves - I assume running rich is clogging up the valves


    I think someone has restored this bike as its in great nick cosmetically and all the rubber on the engine is new and it has very low mileage compared to others I've seen. The previous owner said he bought it with an ignition problem and replaced the coils, and this idle issue is new (but the bike sat in his garage the majority of his ownership).


    Any ideas on if my carbs can be adjusted or if I should cover the airbox holes and re jet back to factory spec? or other ideas?


    Thanks
     
  2. Cbuzz

    Cbuzz Well-Known Member Dirty Wheel Club

    Messages:
    131
    Likes Received:
    54
    Trophy Points:
    233
    Joined:
    Mar 30, 2017
    Gender:
    Male
    Location:
    Australia
    My Bike:
    ZXR250A
    Start putting the stock jets back into it & sealing the airbox. Otherwise it will be tough to get the mix right.

    Get some good pics of the carbs up as well.
     
    • Like Like x 1
    • Agree Agree x 1
  3. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

    Messages:
    8,166
    Likes Received:
    4,832
    Trophy Points:
    1,168
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Troublemaker
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Suzuki GSX250 *Triumph Bonneville 750 T140V
    • Like Like x 1
  4. John McLeod

    John McLeod Member

    Messages:
    5
    Likes Received:
    4
    Trophy Points:
    13
    Joined:
    Mar 26, 2019
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    1989 GSXR 250R
    thanks guys, I'll try to get some pics up soon. Can someone tell me the stock jet sizes? I'm sure I saw it on here before but cant find it again...
     
  5. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

    Messages:
    8,166
    Likes Received:
    4,832
    Trophy Points:
    1,168
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Troublemaker
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Suzuki GSX250 *Triumph Bonneville 750 T140V
    pilot screws

    pilot.png
     
    • Like Like x 1
  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    3,201
    Likes Received:
    1,862
    Trophy Points:
    898
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide, South Australia
    My Bike:
    Yamaha's, 1990 FZR250R 3LN3 , 1986 XT250TS 57R , 1984 IT200L 43G
    • Like Like x 1
    • Winner Winner x 1
  7. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

    Messages:
    8,166
    Likes Received:
    4,832
    Trophy Points:
    1,168
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Troublemaker
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Suzuki GSX250 *Triumph Bonneville 750 T140V
    Yea correct .... I did it in a hurry without my glasses on .... :lolsign: ..... old age I think its called :commando:

    Ill go back to servicing my walking frame :D
     
    • Like Like x 1
    • Funny Funny x 1
  8. John McLeod

    John McLeod Member

    Messages:
    5
    Likes Received:
    4
    Trophy Points:
    13
    Joined:
    Mar 26, 2019
    Gender:
    Male
    Location:
    New Zealand
    My Bike:
    1989 GSXR 250R
    Awesome thank you!! Looks like it might be a bit tricky to get the middle carbs while they are on the bike but I’ll give it a go and post an update
     
    • Like Like x 1

Share This Page