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Help Canadian GSXR250 GJ73A

Discussion in 'Suzuki 250cc In-line 4's' started by JohnRcbr, Aug 6, 2018.

  1. JohnRcbr

    JohnRcbr Active Member Premium Member

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    About a year and a half ago I crossed paths with a poor neglected 1989 Gsxr250. Being the soft hearted fool I am the bike came home with me. Well countless hours of searching for parts and information and hundred of hours of cleaning and wrenching later the bike is back together and on the road. The rusted gas tank was by far the most trouble.
    It seems to run quite rich and was wondering what settings, jets and float height other were using successfully (BDST29 carbs).

    I have 110 mains on the outer cylinders and 105 on the center two cylinders. Low speed jets are 50. Air screws are out 1.25 turns. I had to drop the needles to the lowest position to stop the severe wide open bogging but it still doesn't like to pull much above 10,000 rpm in the top 3 gears. Any help would be greatly appreciated.
    Thank you
    John

    DSCN0185.JPG
     
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  2. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    If it pulls to redline in the lower gears then I would check compression. Your bike looks great by the way, well done.
     
  3. JohnRcbr

    JohnRcbr Active Member Premium Member

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    Thanks your seal kit works great
     
  4. risky

    risky risky

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    welcome and that is one nice bike.
     
  5. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Welcome to the forum

    The low speed jet #50 you mentioned sound like they're the starter jet's
    Pretty sure the GSXR250R should have #15 pilot jet's the look like one's below
    (picture is for the GJ74A Mikuni's)

    What are your float height's set at ?
    How many mm's above the line on the outside of the fuel bowl is the fuel level ?

    1gj74a.jpg
     
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  7. Murdo

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

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  8. JohnRcbr

    JohnRcbr Active Member Premium Member

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    You are correct about the jet sizes. I will blame my error on staying up to late and trusting my memory instead of going out and checking my notes. When I assembled the carbs last May (2017) I didn't have a float measurement to use but they were all the same so I left them like that. Unfortunately I didn't record the height, that is why I am looking for a measurement before I take them apart again.
     
  9. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Nice to see another gj73a , I’m waiting on my barrels to come back from being bored then it is all system go to get mine back on the road
     
  10. JohnRcbr

    JohnRcbr Active Member Premium Member

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    It is nice to see there are other GJ73As out there. I am over 60 and have been riding since my teens and mine is the only one I have ever seen on the road. If I win a lottery I guess a trip down under will be needed.
     
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  11. JohnRcbr

    JohnRcbr Active Member Premium Member

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    It turns out my compression is about half of what could be. The bike runs so nice under 10,000 rpm and starts well so the test results are a bit of a surprise. This may end up being a winter project.
     
  12. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    what compression results were you getting ?
     
  13. JohnRcbr

    JohnRcbr Active Member Premium Member

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    90 to 110psi
     
  14. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Yep, that is a tad low
     
  15. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Your bike looks absolutely gorgeous..all the hours cleaning have definitely paid off :)! Attached is a float height setting diagram from the Suzuki manual..hope it helps. If your bike starts and runs up until 10K rpm and there's no obvious blow by or oil consumption (exhaust smoke), oil filler cap air pressure/ cylinder head breather pressure is normal, test compression under the following conditions;

    Check ALL valve clearances
    Warm engine
    Wide open throttle
    Fully charged battery
    ALL plugs removed

    Post results.

    Before going on the 'winter rebuild project' also look at your compression tester. 90-110 PSI indicates a worn engine, but the cylinder pressures are not massively variant, and the fact that it starts well tells me there's enough compression even when cold for the engine to be fully serviceable. Are you using a push on compression tester or a screw on type..also where is the schrader valve fitted on the tester? The cylinder compression volume is compromised by the guage/valve you use and the length (volume) of the hose and where the valve is fitted. Test when cranking that it meets the criteria of a minimum of 400-450rpm, as otherwise you wont achieve the compression listed as normal in the manual. If you want to check and re check go with a leak down test before you pull it apart..its much more accurate and will confirm prior to pull down that the rings/bores are bad or the valves aren't seating properly..

    Hope this helps,

    Cheers,

    Si
     
  16. JohnRcbr

    JohnRcbr Active Member Premium Member

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    Thanks Simon. I tested the engine cold because it takes so long to strip the tank, fairings etc to get at everything. The carbs where removed so I could check the float height. I had all the plugs removed and tried with two different screw in type gauges. The gauges both have hoses about eight inches long and the valves are just below the gauges. I will be checking valve clearance and crank the engine over with the valve cover removed to make sure things look right before going into the engine.
    John
     
  17. JohnRcbr

    JohnRcbr Active Member Premium Member

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  18. JohnRcbr

    JohnRcbr Active Member Premium Member

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    I couldn't find pictures for this engine so could someone let me know if my pictures look right. The picture of the crank did not turn out good but the "T" line is lined up with the pick up. I am not good at posting pictures so if you can't see them let me know.
    Thank You
    John
     
    Last edited: May 9, 2019
  19. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Picture's all came out clear except the crank shot.
    Maybe try a different angle, or turn the flash off ?
     
  20. JohnRcbr

    JohnRcbr Active Member Premium Member

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    DSCN0274.JPG
    After boring it .25mm oversize and installing new pistons and rings I assembled it with the cams installed how they were before taking it apart. Before I finish closing it up I was wondering if someone who has did this before could tell me if it looks correct. The cam pictures are three posts up.
     

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