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Help Jetting - Suzuki T250J

Discussion in 'Suzuki 250cc 2 Strokes' started by scud57, Feb 24, 2018.

  1. scud57

    scud57 Member

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    Hi Guys,I'm Building a Bike t250 Engine, USD forks, café racer style,Higgspeed pipes,pod filters.I took it for a shakedown ride to check everything works before I break it down for paint etc.She runs but not great,can anybody give me some info regarding jetting etc?
    Cheers Chris.
     
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  2. Murdo

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

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    Welcome to the forum.
    Geez, how long is a piece of string?????
    Before we can even take a guess from this side of the world (and remember that you have heavier/thicker air in the Northern hemisphere) we need to know what has been done to the engine and how it runs now. Has it been rebuilt and have any modifications been done? Do you have original carbs? If so what size (there are two sizes listed by Suzuki for the T250). Does it cough, splutter or just bog down when you open the throttle? What are the spark plugs like, are they new or old gummed up ones. Do you have good even compressions (both cylinder and crankcase)? What type of ignition are you running, points or electronic? If you have those silly little pod filters, are they clean and big enough to flow enough air for the engine and do they have spacers/longer induction tubes? All these things (and more) will effect how an engine runs and what jetting it will need to run correctly.
    Perhaps you could ask Higgspeed what their recommended starting point for the jetting would be and work from there. Work carefully and if the engine doesn't feel or sound right then stop and find out why. It's all a learning experience.
    Good luck.
     
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    Last edited: Feb 25, 2018
  3. Wozza

    Wozza Active Member

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    from the higgspeed site

    "http://higgspeed.com/FREQUENTLY-ASKED-QUESTIONS-FAQ-

    THE QUESTION OF WHETHER YOU NEED TO REJET, IS LARGELY DEPENDANT ON WHETHER YOU ARE RUNNING THE COMPLETE STOCK AIRBOX.
    F YOU HAVE REMOVED THE AIRBOX AND FITTED INDIVIDUAL OR POD FILTERS ,YOU WILL DEFINATELY NEED TO REJET, TYPICALLY AROUND 10 SIZES UP.
    MOST OF MY PIPES ARE DESIGNED TO RUN ON STANDARD JETS, BUT ONLY IF THE ENTIRE AIRBOX AND ASSOCIATED INLET TRUMPETS ARE INTACT AND IN GOOD ORDER. I.E. NOT LEAKING AIR OR CRACKED RUBBERS
    MANY BIKES HAVE A STOCK AIRBOX, WITH SOME KIND OF REMOVABLE INLET TRUMPET OR RESTRICTOR. IF THIS HAS BEEN REMOVED ON YOUR BIKE, IT WILL NEED TO BE REJETTED WITH LARGER MAIN JETS (TYPICALLY UP 3 SIZES) ,BUT CHECK YOUR MAIN JETS AS IT MAY WELL HAVE BEEN DONE ALREADY.
    THIS MAY SOUND VAGUE BUT DONT FORGET THESE BIKES ARE AROUND 40 YEARS OLD. THE GOLDEN RULE IS, IF IN DOUBT FIT LARGER MAIN JETS AND CHECK THE PLUG COLOUR, YOU CAN ALWAYS COME DOWN IF NECESSARY. "

    carb info you should find here
    http://www.oldjapanesebikes.com/mraxl_GT_Resource/manuals/specs/index.php
     
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  4. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Welcome. If you have some time, watch this YT video. It may help.

     
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  5. Wozza

    Wozza Active Member

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    You do know his video's mostly are taking the pi$$...also the carbs on the sussie is slide not cv :D
     
  6. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Sorry, didn't realise they were different style carbs. Someone sent me the link and it seemed to make sense. Ignore the post.
     
  7. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  8. scud57

    scud57 Member

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    Thanks for your responses,here is a bit more information. The engine has been completely rebuilt,crank,rods,pistons,seals,bearings and rebore +.5. I have fitted a powerdynamo ignition,it has standard vm24hs carbs with new main jets 10 sizes up as suggested by Dave at Higgspeed,the plugs are B7hs.I had another look at the plugs this morning both look ok but when I looked at the piston crowns through the plug hole one is bone dry whilst the other is a little wet.Is it possible that one carb is not delivering enough fuel?
    Cheers Chris.
     
  9. scud57

    scud57 Member

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    Couple of pictures of project

    20180120_114204.jpg 20180120_114239.jpg 20180120_114327.jpg 20180120_114335.jpg 20180120_114510.jpg
     
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  10. Murdo

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

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    Looking good so far. :thumb_ups:
    How have you synced the carbs? Are both pipes getting hot equally after running for 30 seconds or so?
    We still don't know how the bike is running, what are the symptoms?
     
  11. scud57

    scud57 Member

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    Hi the bike idles really well but doesn't really run cleanly, particularly in the mid range its a bit inconsistent,it did pick up nicely at around 5000rpm and sounded really good but then ran out of steam. Also any ideas on speedo tacho arrangement as the speedo I have fitted is completely the wrong ratio.
    Cheers chris
     
  12. Murdo

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

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    Suggest that you drop the carb needles (that is move the circlip up the stem of the needle thereby dropping the needle down further into the jet) one notch and try it again. If better but still not right then drop them another notch and see. If no better then put circlip back to centre position and reduce the main jet size by two sizes, then try again.
    It is all try and error as each engine will be different.
     
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  13. scud57

    scud57 Member

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