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Project The Second Fizzer

Discussion in 'Your 250cc Projects' started by Joker, Sep 28, 2016.

  1. Joker

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

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    PM me details mate :)
     
  2. Joker

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

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    Hmm. A play last night, I swapped the carbies from the mexican fizzer over to no real improvement. Took a bit longer to start but it seemed to idle reasonably well (albeit not as well as with the other carbies). Coupled with that, the mexican fizzer runs without a fuel pump... not sure how that is possible but it did. I'm now inclined to think this is not a fuel related issue but either be weak spark or something to do with the top end (either choking exhaust gas flow by the EXUP, which I doubt because I removed the exup before to no improvement OR something to do with the valves.)

    Next step is to swap the coils out for the mexican fizzer ones that I know are good and see if there is an improvement, after that, I'll try and swap the headers to see what that does otherwise the valve cover comes off and I'm into clearances again. it can't be the new rings, I followed the same process on the Phazer and that ran much better (and was in more questionable condition than this bike).

    Lots of fun, for sure.
     
  3. Joker

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

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    After thinking about it, I should add that it is unlikely to be the EXUP as that has a higher effect on low RPM and the bike seems to run fine in that throttle range.
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Try bridging the 2x wire's from the side stand switch,
    might be high resistance and not letting enough power through to the TCI and ignition coil's.
     
  5. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Could also be the 180km/h limiter. Unsure how to bypass it on the fizzers as I never felt the need
     
  6. Joker

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

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    In the first place it was revving fine at idle, now it is worse. These carbies are off the other running bike though. Seems wet in the slide area, is it flooding perhaps? settles back into idle fine though, doesn't cut out. The other carbies run the same.

    Running out of ideas now, short of looking at the valves again. Coils replaced from other bike and same result. Fuel levels may help but given scenario is the same from both carbies with no improvement I don't want to start messing with them.

    If I only knew the problem I could bloody well fix it, so frustrating.

    Don't know about the rev limiter, but the bike ran fine with the old engine and I haven't changed it... so not sure it would be an influence?
     
  7. Joker

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

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    Someone mentioned blocked tank breather... curious...
     
  8. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Just leave the fuel cap open while running to test if the breather is working or not
     
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  9. beano

    beano Well-Known Member Premium Member

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    The two things i have learned from this forum over the last year or so that i've been here and from my own rebuild is that firstly its really really important to actually diagnose the problem before you go ripping it apart and changing everything, and secondly, KEEP IT SIMPLE!! fuel, air, spark and compression are all an engine needs and all of these things are measurable and should be measured before changing the respective parts.

    If i were you the first thing i would do is a compression check, depending on the type of compression tester, it can be hard to get an accurate reading for a small capacity cylinder. The first (cheap ebay) one I had would under-read by somewhere around 30-50% vs a proper pro one on a 50cc cylinder. Down to the volume of air in the tube between the spark plug hole and the size of internal reservoir in the gauge itself. Smaller the cylinder, the greater the error in the compressed volume/pressure. I found with the cheaper ones that the number doesn't matter per se just as long as they are all even-ish.

    Then its the carbs, you know yourself what they're like but my 2 cents are that setting the correct fuel level made the single biggest difference to boggy acceleration and poor high RPM running in my machine, best of luck with it, hope you get her goin!!
     
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  10. kiffsta

    kiffsta Senior Member

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    Throw a meter across the battery when you are revving it up and make sure the electrical system is not breaking down under load , I’m also thinking ignition advance , is there any difference between cdi’s. Because this is a replacement engine from a 3ln1 and your running a 3ln3 , is it worth ensuring you have the correct cdi for that engine , they Could be the same but I am not sure.
     
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  11. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I measured a 2KR stator and pick up coil and compared it to my 3LN3 stator and pickup coil and got pretty much the same reading's from both

    In your video it looked like the slide's weren't moving at the same speed, carb sync? or mixture's ?
     
  12. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    If you've migrated carbs, with the fuel level set correctly, from a bike with a fuel pump to another without a fuel pump, or vice versa, then I'd say odds on that fuel level is wrong - check it before you delve any deeper
     
  13. Joker

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

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    Ok so today I had another play.

    Fuel cap open - no effect
    Swapped tank - no effect
    Swapped CDI - no effect
    Bridged Side Stand Switch - no effect

    Digging further into the "lean" issue... taped off 2/3 of the carburetor inlet with masking tape. dribbled some fuel into the carbies and bang, revving up to 18.5K. Progress of some sort. Next port of call is to richen the needles again and test it under load, if we have some improvement then we're on the right track and I can move to fine tuning activities.

    Seems like I've done a full circle back to the carburetor, but all the opinions helped as I knocked off a lot of possible influences.
     
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  14. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    What position are your needles on? Any washers/shims underneath the clip?
     
  15. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Check the float level's might be a little low?
    Moving the needle clip's will just change the mid rev's
     
  16. Joker

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

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    @Linkin I have to double check that. I think there is a plastic spacer/shim/washer thing under each clip, that's the way it has always been.

    @my67xr I'm getting there, plan to check that tonight.
     
  17. Joker

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

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    Well needles on richest setting puffs out black smoke at top end. Battery and charging system seems ok. Float levels bang on. Only thing left is top end... will test ride again and loop back...

    20171214_193538.jpg
     
  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    So they are 3LN3 carby's ?
    My fuel level's are about 10.5mm above the line, float height's are 14.7mm
     
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  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    That's good to know for two reasons -
    1: because I don't recall the 3LN3 numbers being published anywhere official so gives a good starting point.
    2: 3LN1 numbers are 16mm float height which yields 9.2mm fuel height - the addition of these two numbers yields 25.2mm
    The 3LN3 numbers you've given 14.7mm float height and 10.5mm fuel level - these also sum to 25.2mm

    So for anyone wanting to make accurate adjustments it looks as though within that range measuring one should give a fairly accurate prediction of the other - makes the procedure just that little bit simpler and faster

    Fzr250 Fuel level/float height
    Float height + fuel level = 25.2mm

    Tag for searches FZR250 fuel level float height
     
  20. Joker

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

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    Yes they're 3LN3, I have another 3LN3 set and a 3LN5 set that I'm going to rebuild when I can be bothered.

    Bike started and revved cleanly but now won't even idle but will start and sounds like it's struggling for fuel. The fuel line is empty, the fuel pump seems to be playing up again. it seems to choose to operate when it feels like it. Just have to wait it out.

    I'm curious though, has anyone else ever rigged an FZR fuel tap to operate WITHOUT the fuel pump? the mexican fizzer is a strange one, there is two lines coming from the tank into the tap and one going from the tap to the fuel filter. Somehow, the line from the tap to the filter was swapped with one from the tank to the tap, and only on reserve there is a free flow of fuel. Such a strange set up... the bike seemed to run OK before I got it but I can't figure out how this setup would be sustainable.
     

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