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Help Help with a hesitiating/missing Across

Discussion in 'Suzuki 250cc In-line 4's' started by Arch_Althalus, Jan 17, 2019.

  1. Arch_Althalus

    Arch_Althalus Member Premium Member

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    Hi, I am fairly new to the forums but have been reading up on the threads regarding hesitation and carby issues as I have hesitation between 4 1/5 to 6k rpm. On the advice in those threads i have pulled the carby's out twice, cleaned the main and pilot jets, cleaned the needle ject and checked on the jet needle, spring, holder etc and they all seem to be operating within the workshop manuals specifications. Given this has exhausted my limited mechanical knowledge I am wondering if anyone has any other thoughts? Otherwise it is off to a mechanic she goes.

    I have -
    Cleaned the main jet
    Cleaned the pilot jet
    Cleaned the jet needle (was very blocked)
    Cleaned the fuel filter, and drained tank to get rid of any crap in it
    Checked the diaphram
    Checked the jet needle, spring, and holder to ensure all were good (as per workshop manual)
    Cleaned air filter and after each re assembly checked seals to ensureits not sucking any air.

    Any help would be appreciiated.

    Thanks

    Althalus
     
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  2. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    Have u checked the intake boots for cracks or leaks?

    across boots.png

    intake rubbers.jpg
     
  3. Arch_Althalus

    Arch_Althalus Member Premium Member

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    Yeah, i had a look over them, but they look like they have not long been replaced. Think I might have got someones lemon.
     
  4. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    strange one, Across's only bog down if the air fuel mix screws are set incorrectly or a slide holder has fallen, these carbs can be a bit tricky to setup, maybe a trip to a mechanic is on the cards as you don't know what the last owner did to them.
     
  5. Arch_Althalus

    Arch_Althalus Member Premium Member

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    A supposedly mechanically minded friend has suggested a compression test to see if the valves are where they should be. It will have to be a while if I need to see a mechanic as its not somethign I can afford right now after buying the bike and replacing all my riding gear that perrished from sitting in the shed.
     
  6. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    Maybe someone has fiddled with the jets and more ... does it have the correct size jets and the pilot screw is set to default as mentioned ?

    Is the pilot screw washer and o ring setup correct?

    PilotScrewAssy.jpg

    across spec.png
     
  7. Andych

    Andych Well-Known Member Premium Member

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  8. Arch_Althalus

    Arch_Althalus Member Premium Member

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    I had a read through that but what is the emulsion tube? I think it will just havd to wait till I have the moeny and take it in to a mechanic. Thanks for the advice everyone, I appreciate the responses.
     
  9. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Just curious if your air box is correctly
    Installed , they can be a pain to fit properly
     
  10. Andych

    Andych Well-Known Member Premium Member

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    And the carbys can also be a pain to fit back properly... if they are not pushed all the way into the manifolds you will get some serious air leaks.. Have you tried spraying some WD40 around the carby mounts while it is running.. see if the revs change at all.
     
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  11. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    Just tread carefully if u do end up at a mechanic ... alot wont touch old bikes , alot have no clue on old carby bikes and if they start doing 'carby overhauls' then be prepared to sell your kidneys to cover the bill

    When refitting carbys or airbox rubbers smear a small amount of rubber grease on the contact areas so everything goes on (and off) easier

    An emulsion tube is also called a needle jet as it just plays a part in the rev range just like the other jets ... it just happens to be a tube with a needle going up and down in it ... which just happens to be called the 'jet needle' :D

    https://www.2fiftycc.com/index.php?resources/needle-jet-wear.290/

    https://www.2fiftycc.com/index.php?resources/principles-of-motorcycle-carburetor-function.117/

    carb_jet_usage1.jpg
     
  12. Arch_Althalus

    Arch_Althalus Member Premium Member

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    I have been wd40 spraying each time I re-fit the carbys and airbox. I have a guy I used to use back with my zxr250c, so I know he is good, just costs and arm and a leg. After all the work I have done with the carbys I am really thinking its the valves which is way outside my knowledge.
     
  13. Andych

    Andych Well-Known Member Premium Member

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    Sounds more like you have an issue with the Vacuum slide clips or the diaphragms.. they are typical failure points on the Across.
    They are not hard to check.. even with the carbies in place.. you also need to make sure the fuel pump is working properly and that the fuel filter isnt blocked.. Plus check the float levels..
    These carbies are not really that difficult.. that link takes you on a step by step guide to stripping them down and cleaning them up.. it is imperative that you make sure you can see through any jet you remove.. the tiniest bit of crud can cause the biggest nightmare at times.. but.. there is a great sense of satisfaction when you have pulled them down.. cleaned them out and it runs.

    You could do a compression test as well.. that will give you a bit of an idea about valve clearances and / or general engine condition but these things are normally pretty much bulletproof under normal circumstances.
     
  14. Arch_Althalus

    Arch_Althalus Member Premium Member

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    So to update, the pilot screws are worn, so I will replace them, I am going to replave the holders out of principle, and so i know they are good. The needle valve looks brand new and beautiful. And as I went to remove the pilot jet to do a full soak as opposed to a basic clean it seems the joker bwfore me actually tightened them that hard he chewed the opening off it, so I had to remove one of them with an easy out. Ordering the parts tonight and will let you know how it goes after the repairs. Thanks so much for the advice, i am learning as I go and this is getting easier.
     
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  15. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    Yea way to go ... carbs look daunting to begin with but they are pretty simple once u do it a few times and understand them

    Not unuusal for pilot jets to be mashed up as they are very soft brass and of course slotted ... they can be stuck hard from age but people overtighten such things where as they are just jets and fittings in a carb so they dont need 100nM of torque

    Multi carbs are fairly hard to get right at most times , especially older ones , so perserverance and plenty of cursing and head banging, is required ...... u can see the amount of 'carby' posts and threads on this forum :D

    We all start at the beginning so just keep at it and keep asking questions :thumb_ups:
     
  16. Murdo

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

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    I would be checking/setting your valve clearances then compression testing before any effort to try and synchronize the carbs, otherwise you will be looking for the wrong faults.
     
  17. Arch_Althalus

    Arch_Althalus Member Premium Member

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    If I had the tools and the know how I would do the lot, but I am working through what I can do/read how to do and what I can afford. If this fails the Across is off the road till I can save up enough to put it in somewhere.
     
  18. Arch_Althalus

    Arch_Althalus Member Premium Member

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    So the new pilot needles, pilot jets and holders are installed and while it is running better it has not resolved the issue. Thanks everyone for your help, but I am now saving up for a trip to the mechanics.
     
  19. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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  20. Arch_Althalus

    Arch_Althalus Member Premium Member

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    I replaced the slide holders when I did the jets and needles. I am going to order a balancing kit for the carbys. Does anyone know if I need a 2 guage or 4 guage kit? I know there are 4 cabys but they are balanced in pairs so I was a touch unsure. Cheers.
     

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