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

Project GSX250 restoration

Discussion in 'Your 250cc Projects' started by SwarleyAUS, Mar 21, 2017.

  1. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

    Messages:
    6,397
    Likes Received:
    4,785
    Trophy Points:
    1,148
    Joined:
    May 4, 2013
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Tamworth, NSW
    My Bike:
    1937 Royal Enfield 250, CF Moto 250 V5, Honda's XL250, CBR250, FT500 plus a few others.
    Much better looking. :thumb_ups:
     
  2. kiffsta

    kiffsta Senior Member

    Messages:
    9,066
    Likes Received:
    6,872
    Trophy Points:
    1,168
    Joined:
    Aug 7, 2010
    Gender:
    Male
    Location:
    Brisbane
    Looks great mate
     
  3. Alipture

    Alipture Active Member

    Messages:
    17
    Likes Received:
    16
    Trophy Points:
    173
    Joined:
    Apr 19, 2015
    Gender:
    Male
    Location:
    Pascoe Vale, Melbourne
    My Bike:
    '83gsx 250
    oh ****, nice job!
     
  4. SCS

    SCS Member

    Messages:
    10
    Likes Received:
    8
    Trophy Points:
    13
    Joined:
    May 6, 2017
    Gender:
    Male
    Location:
    Perth
    My Bike:
    Suzi GSX250
    Great work, it looks great. I have the same model and you've inspired me with all your hard work and perseverance.
     
  5. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Thanks, keen to see what you do with yours! Still got some work on the cards: pods, new seat & tail loop, tidy electrics, etc but wanted it road legal asap. As such I may have a seat for you in the coming months if still needed!
     
  6. SCS

    SCS Member

    Messages:
    10
    Likes Received:
    8
    Trophy Points:
    13
    Joined:
    May 6, 2017
    Gender:
    Male
    Location:
    Perth
    My Bike:
    Suzi GSX250
    Funny you should say that, I've been chasing one for a little while, though it will only be needed temporarilyuntil I get cracking on my cafe racer conversion too.
     
  7. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Can anyone help me read the plugs pretty please? I'm useless at it.

    Trying to tune for pods - just replaced the stock 17.5 pilot with a 20. Struggles to rev from idle to 2k (but better than it was on stock pilot). Bogs at 5k which I hope to resolve with a larger main jet once she's idling safely.

    Before & after 2 minute run:
    19403620_10213623086390223_1308672450_o.jpg 19401221_10213623086590228_2110282336_o.jpg

    I think the after looks ok right? Bit of tan colour to the porcelain which is ideal I believe? External cylinder temp was ~60C after 2 minutes.
     

    Attached Files:

    Last edited: Jun 20, 2017
  8. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    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, 1976 IT400C 510
    What sort if pods are you running?
    If you are using pod's that cover the air jet on the carby inlet it'll cause problem's
     
    • Like Like x 1
    • Informative Informative x 1
  9. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Foam ones without restriction, as oppose to the mesh cone ones, at the moment. Yep I've trimmed the rubber flange to allow airflow.
     
    • Agree Agree x 1
  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    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, 1976 IT400C 510
    To me they look ok, but how many turn's out on the mixture screw's ?
     
    • Like Like x 1
  11. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    1.5 turns on each carb. Ok cool thanks for your input. I think it might still be a pilot jet size or two lean and judging by the lack of any soot or colour on the end of the plug thread I think this confirms that fact(?). Perhaps I just need to a run it a lot longer than 2 minutes =)
     
  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    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, 1976 IT400C 510
    Yeah setting mixture's you really need it at operating temperature
    You can at least go up one size on the pilot's and still will be under 2.5 turn's out
    Have you oiled the foam filter's ? or are they still factory oiled ?
    I use foam Uni Filter's on my race pit bike's and IT200, and spray them with a light coat of Castrol foam filter oil
     
  13. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Yeah I'll definitely go up a size to try to resolve poor throttle response. If I see some soot to then I'll also feel at ease that it's not running lean.

    Yeah I oiled them first.
     
    • Nice Work Nice Work x 1
  14. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    I just used engine oil =/

    It is interesting now I think about it... as the mixture screws are 1.5 turns out this infers the air/fuel ratio is ok, right? As 1.5 turns is where they should be with stock airbox.
     
  15. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

    Messages:
    6,397
    Likes Received:
    4,785
    Trophy Points:
    1,148
    Joined:
    May 4, 2013
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Tamworth, NSW
    My Bike:
    1937 Royal Enfield 250, CF Moto 250 V5, Honda's XL250, CBR250, FT500 plus a few others.
    You need to get the main jets right first, then work back to the needles and then pilots.
     
  16. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Hmmm interesting, that's what I've read but I don't understand a) how that's safe given the bike is at idle most of the time (I don't want to sieze the engine trying to determine main jet sizing whilst it's idling lean) and b) why you wouldn't start with the pilot jets as they effect the air/fuel mixture across the whole rev range?

    upload_2017-6-21_8-41-43.png
     
  17. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

    Messages:
    6,397
    Likes Received:
    4,785
    Trophy Points:
    1,148
    Joined:
    May 4, 2013
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Tamworth, NSW
    My Bike:
    1937 Royal Enfield 250, CF Moto 250 V5, Honda's XL250, CBR250, FT500 plus a few others.
    Well, the fuel has to come through the main to get to the needle jet and as your drawing above shows the main still has an effect from below half throttle upwards. Get all your pilots right and idling nicely, then when you change the main you will have to alter the pilots again to get it idling.
    Depend on how many times you want to pull the carbs to bits changing jets.
     
    • Informative Informative x 1
  18. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    Weird, I didn't think changing the main jet should effect the idle at all (idle being 0% throttle)? If so, so be it, it's a learning experience!
     
  19. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

    Messages:
    4,313
    Likes Received:
    2,383
    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, 1976 IT400C 510
    I have found that using engine oil on the foam filter's it get's sucked off the foam and into the throat's of the carby's
    Proper filter oil is cheap, (supercheap have it for about $11 for a spray on can of Castrol)
    Filter oil is kind of sticky so it trap's any dirt etc before it can move through the foam, and it also help's to make your mixture's slightly richer.
    Getting the pilot's close will help the tuning, but they may need to be changed again when it's tuned properly after jetting the main's.

    4 stroke are a lot more forgiving than 2 stroke's with jetting
     
    • Like Like x 2
    Last edited: Jun 21, 2017
  20. SwarleyAUS

    SwarleyAUS Well-Known Member

    Messages:
    141
    Likes Received:
    64
    Trophy Points:
    213
    Joined:
    Mar 11, 2017
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Cheltenham, Melbourne
    My Bike:
    Suzuki GSX250
    So can anyone explain to me why changing the main jet effects the idle mixture?

    "The pilot jet is the part which supplies most of the fuel at low throttle openings. It has a small hole in it which restricts fuel flow though it. Both the pilot air screw and pilot jet affects carburetion from idle to around 1/4 throttle...

    The main jet controls fuel flow from 3/4 thru full throttle, fig 5. Once the throttle is opened far enough, the jet needle is pulled high enough out of the needle jet and the size of the hole in the main jet begins to regulate fuel flow. Main jets have different size holes in them and the bigger the hole, the more fuel that will flow (and the richer the mixture)." From http://www.iwt.com.au/mikunicarb.htm
     

Share This Page