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Stu's Fizzer

Discussion in 'Your 250cc Projects' started by Joker, Jan 12, 2015.

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  1. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Jets have the sizes stamped on them

    MikuniJets.jpg

    Mikuni logo

    MikuniEmblem1.jpg
     
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    GreyImport, Jul 15, 2016
    #361
  2. Joker

    Joker See "about me" for contact details. Contributing Member

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    Thanks mate. I haven't actually paid that much close attention before. Will now, definitely.
     
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    Joker, Jul 15, 2016
    #362
  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Mine has #100 main jet's on the outer carby's and 97.5's on the inner 2 carb's
    1 and 4 carby's use the 5CT7 needle, and carby's 2 and 3 use the 5CT9

    Put the jet's on a table and use your phone to zoom in and focus on the number's, it's a lot easier than squinting, lol
     
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    my67xr, Jul 15, 2016
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Jul 15, 2016
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  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Nice,
    i have the A4 budget version, magnify's it 3 time's, $3 from the Indian cheap shop's
    Zooming in on the phone is much easier

    [​IMG] [​IMG]
     
    my67xr, Jul 15, 2016
    #365
  6. Joker

    Joker See "about me" for contact details. Contributing Member

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    Might need my old man glasses for that one haha. Can't be bothered pulling the tank again at the moment will look at it when I can because if things are mixed up it sorta explains a couple of little things.

    The other issue I'm having is that running the bike there's a moderate smell of fuel coming from under the tank. It's not leaking anywere, I assume it's probably because I sealed the airbox to the carbies so there's nowhere else for it to go. Richness doesn't seem to be a big issue at the moment... any thoughts on what that could be?

    Hey GI, I remember reading somewhere you found that a suzuki diaphragm fits these carbies right? I can't seem to find the post... can you please point me in the right direction? :D
     
    Joker, Jul 16, 2016
    #366
  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Jul 16, 2016
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  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Check all the fuel hoses and the fuel tap especially for leaks... If the tank is completely full it might be letting fuel out the overflow/drain tube.
     
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    Linkin, Jul 16, 2016
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  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    check me on this however I seemed to recall smaller jets on the inner cylinder pair because the air in the intake tract is subjected to more heat, therefore expands more requiring less petrol for correct fueling

    larger jets on the inner would run them richer than necessary and smaller ones on the outer would run them leaner

    I don't have the official Fizzer documents to hand, best to refer to them to be certain

    OK just checked
    Main Jet sizes
    102.5 cylinders 1 & 4
    100 cylinders 2 & 3

    Page 27 of this document
    http://2fiftycc.com/index.php?resources/yamaha-fzr250r-3ln1-service-manual-supplement.11/
     
    ruckusman, Jul 16, 2016
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  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yep that's right but the 3LN3 uses's smaller main jet's #100 on the outer 2 carb's and #97.5 on the inner 2 with the BDST28 Mikuni's
     
    my67xr, Jul 16, 2016
    #370
  11. Joker

    Joker See "about me" for contact details. Contributing Member

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    So on the way to work this happened...



    :commando:

    Managed to get the last 3 or 4 kms to work but will have to trailer it home as I'm not comfortable riding like that. Just so gutted... suppose I'll have to pull the engine out for this investigation....
     
    Joker, Jul 21, 2016
    #371
  12. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    check the EXUP valve is moving and doesn't have a frayed cable
    Been a long time since it happened to me however my EXUP cable frayed, it wouldn't actuate it wouldn't rev and sounded awful and had nothing power wise
     
    ruckusman, Jul 21, 2016
    #372
  13. Joker

    Joker See "about me" for contact details. Contributing Member

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    The engine ticking and clunking doesn't sound good to me either... need to check both the top and bottom ends but while I'm at all of that I might as well do bloody rings and rebuild the thing. Really was hoping I wouldn't have to do that.
     
    Joker, Jul 21, 2016
    #373
  14. MashtX

    MashtX Well-Known Member

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    That doesn't sound good at all :/ thankfully if the 250 is anything like the 400, they are simple enough to remove and tear down... hope it's just something simple though!

    Sent from my HTC_0PJA10 using Tapatalk
     
    MashtX, Jul 21, 2016
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  15. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The noise sort of sound's like timing chain/tensioner to me.
    If you take the centre bolt out, then the 2x outer bolt's, carefully pull the tensioner out the engine without it dragging the pusher rod out.
    The spring loaded pusher rod in the middle should only be sticking out a bit with you fitting a new timing chain.
    If it's out more than that then that might be your problem.
     
    my67xr, Jul 21, 2016
    #375
  16. Joker

    Joker See "about me" for contact details. Contributing Member

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    Thanks, I did the chain a couple of weeks ago and it had been fine on many hours riding since then - I'll take a look, hopefully it is just the chain...

    A good friend of mine has the following to offer after viewing the video...

    "The deep knocking sound is a flogged out Conrod bearing. And it's the Conrod basically smacking your crank exciting the deep natural frequency of the crank. As the crank is a large item, hence the lower deep sound. the high pitch tick, again same methodology is a small items natural frequency being excited from a impact. Due to extreemly tight tolerances on the piston to valve movement to get the high performance, this extra slap on the bearing causes the piston to extend higher in the stroke and it's just slightly hitting one of your valves as its opening. Don't ride that bike or start it anymore! It will snap a valve and bugger the crank bearing journal more..."

    Yay.
     
    Joker, Jul 21, 2016
    #376
  17. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's a big end bearing for sure.
     
    Linkin, Jul 21, 2016
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  18. Joker

    Joker See "about me" for contact details. Contributing Member

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    Just what I needed. Hmm...

    Any advice on sourcing bearings or does anyone know where I may be able to get my hands on a decent bottom end (short motor)?
     
    Joker, Jul 21, 2016
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  19. risky

    risky risky

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    bearings- alibaba.
     
    risky, Jul 21, 2016
    #379
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Take the head and barrels off and check for vertical play in the rods to find out which cylinder had the failure. From there splitting the cases is just undoing the bolts from highest number to lowest, keeping them in order for re-assembly.

    When this happened to mine I just used another crankshaft and rods, with new main bearings. The rods were fine so I left them alone. You will need to have the crank checked at a machine shop against the service limits in the manual.

    The crank should have numbers stamped into it that tell you what size bearings are in it. That gives you most of the info to order new bearings. The damaged journal, if saved, will need to be miked and have the oil clearance checked with multiple sets of bearings.
     
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    Linkin, Jul 21, 2016
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