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Help GSX250 - carb issue again any thoughts

Discussion in 'Suzuki 250cc Twins' started by gainey, Sep 18, 2015.

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  1. gainey

    gainey Active Member

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    hi everyone,

    since we thought we were finished the starter motor died and the carbs kept having the high idle, so we got another starter and another set of reconditioned carbs.
    because we put pods on we have drilled out the main jet, and idle jets in the carbs with proper jet drills and went one size bigger. for the last couple of days it starts 1st time no worries idles great and then when you rev it hard it stays it high idle and will slowly drop a little, ( I have attached a video after a quick ride around the block this arvo)



    , so we put the old jets back in and now it wont start, it seems to back fire out the carbs...aaaahhhhhhhh

    any thoughts would be great

    cheers
     
    gainey, Sep 18, 2015
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  2. Murdo

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

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    Next time it is idleing at high revs, try a bit of choke. This will tell you if it is too lean and needs richening up.
     
    Murdo, Sep 18, 2015
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  3. Willrcr15

    Willrcr15 Well-Known Member

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    I think your going to have to make up an air box of some sort, CV's just wont run without one. It'll be an interesting exercise experiment.
    Extract from Wikapedia
    Helmholtz resonance finds application in internal combustion engines (see airbox), subwoofers and acoustics. Intake systems described as 'Helmholtz Systems' have been used in the Chrysler V10 engine built for both the Dodge Viper and the Ram pickup truck, and several of the Buell tube-frame series of motorcycles.
    In some two-stroke engines, a Helmholtz resonator is used to remove the need for a reed valve. A similar effect is also used in the exhaust system of most two-stroke engines, using a reflected pressure pulse to supercharge the cylinder
    It's why 2 stroke exhausts are shaped like that, bulging round shape & the out a small end.
     
    Willrcr15, Sep 18, 2015
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  4. gainey

    gainey Active Member

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    hi guys thanks so far, when I pull the choke the idle drops straight down
    I have the carbs set at 2 turns out
     
    gainey, Sep 18, 2015
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  5. Murdo

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

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    May have to go another size up on your pilot jets.
     
    Murdo, Sep 18, 2015
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  6. Evo

    Evo Well-Known Member

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    Been going through the same sort of issues myself. First thing ensure carbs are super clean and good seal all round. I changed to 127.5 main and 22.5 pilot. Needle position is stock (I believe) in the middle.
    Disclaimer. I am no expert and this is through trial, error and research. No idea if I am running rich, lean, or whatever. What I do know is evedent in the attached.



     
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    Evo, Sep 18, 2015
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  7. gainey

    gainey Active Member

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    great thanks
     
    gainey, Sep 18, 2015
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  8. gainey

    gainey Active Member

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    Hey Eco just want to check something when you say 127.5 for the main jet that is the size of the drill? And did u drill out all the holes?
    And how many jet sizes did u go up
    Cheers
     
    gainey, Sep 19, 2015
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  9. Evo

    Evo Well-Known Member

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    No. I did not drill out. Got new jets for both main and pilot
     
    Evo, Sep 19, 2015
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  10. Murdo

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

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    Not a fan of drilling jets as sometime later I will forget what size I had drilled them. Would rather go and buy new ones of the correct size.
     
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    Murdo, Sep 19, 2015
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  11. gainey

    gainey Active Member

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    Hi guys we eventually got it to run better by putting the main jet at 127.5 and it wouldn't run properly we left the idle jet as stock we did put a bigger one in but it just fowler the spark plugs. Our issue now is that if you go for a ride it gets a few flat spots but if I stop somewhere the bike eventually just dies????
    I was thinking of putting some pipe from the carbs to the pods just extending the out say 150mm .... What do you think ?
     
    gainey, Oct 13, 2015
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  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Try an elbow ...

    629073322_o.jpg
     
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    GreyImport, Oct 13, 2015
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  13. Phil

    Phil Senior Member Contributing Member

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    Don't disagree with the concept however I wonder about the available space to accommodate the elbows, your thoughts??
     
    Phil, Oct 13, 2015
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  14. gainey

    gainey Active Member

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    Space is tight we just put an extension of pvc pipe out of the carbs to to the pods and it starts but then won't idle properly you can set it at say 1500 and then rev it a little and it will go up to 30000 and then slowly drop and stall
     
    gainey, Oct 13, 2015
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  15. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    I havnt done any of this but just from memory reading about it somewhere ..... the elbows act to alter the flow of air ( I guess like an airbox in principle) so the inflow isnt direct
     
    GreyImport, Oct 13, 2015
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  16. gainey

    gainey Active Member

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    Groovy thanks
     
    gainey, Oct 13, 2015
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  17. Willrcr15

    Willrcr15 Well-Known Member

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    Put the old air box back on just for a laugh !
    I'll bet she's good then.
     
    Willrcr15, Oct 14, 2015
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  18. gainey

    gainey Active Member

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    Yeh I bet so as well it's just that we built a little box under the seat to house the electronics the bike is painted and done but now deciding to play up ...,, ahhhhhh the barn find
     
    gainey, Oct 14, 2015
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  19. gainey

    gainey Active Member

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    We set the bike to idle at 1500 rpm we went for a ride last night it was a little sluggish and when we got back the bike idled at 1500 then jumped to 2000 and then up to nearly 3000 and then slowly dropped back down and then slowly back up a little I took a video but it would upload from my phone so I will try again later
    I have looked to order a pair of carb boots as the ones are old in case they have a leak and we are going to put the next size idle jet in and we also put a filter inside the carb boot to restrict the air as if it was the box any other thoughts cheers for everyone's input
     
    gainey, Oct 14, 2015
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  20. Willrcr15

    Willrcr15 Well-Known Member

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    CV's need a quantity of controlled air to call on via the air box, the box holds a measured quantity that isn't subject to variation.
    You'll never get it to work nicely without it or some form of controlled flow.
    I don't know but maybe your on something with the longer inlet tubes, I'd try some 40 or 50mm hose about a metre long at first & see if it helps. Maybe bend then around to face the front as ram tubes with gauze to stop the birds getting sucked in.
    Otherwise I'd be after a set of slide carbies of an old trail bike/s & ditch the CV's
     
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    Willrcr15, Oct 14, 2015
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