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Project Linkin's FZR250R 3LN3

Discussion in 'Your 250cc Projects' started by Linkin, Jan 31, 2015.

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  1. Th3_Huntsman

    Th3_Huntsman Senior Member Contributing Member

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    you did say above that the idle hangs abit like that stu..... Contradiction ;)
     
    Th3_Huntsman, Jul 3, 2015
    #681
  2. Joker

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

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    I never said that was a problem though. Some people have inferred it is a problem.

    Plus, it may not be related to the carbs if it is a problem :)
     
    Joker, Jul 3, 2015
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  3. Th3_Huntsman

    Th3_Huntsman Senior Member Contributing Member

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    haha, you should get better fuel economy being a tad lean at idle ;) as long as its smooth everywhere else you'll be right. This notion that pilot screws effect the whole rev range irks me though. on these 4 cyl 250s its to about 8krpm then its all main jets baby.
     
    Th3_Huntsman, Jul 3, 2015
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  4. Joker

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

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    Yeh. Mine's actually slightly different though. It doesn't hang on the throttle, but when you twist the throttle and let go it drops back but the bike does idle slightly higher for a few secs before dropping back down. I think it's probably related to some old air hoses, honestly the connection between the carby and the airbox isn't that great so I wouldn't be surprised if there's a bit of an airleak there doing something a little strange with the air pressure draw.

    But then again I'm probably over thinking it, it's a 25 year old bike who really cares as long as it performs well when riding I'm not gonna spend half my life tinkering to get it perfect lol.
     
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    Joker, Jul 3, 2015
    #684
  5. Th3_Huntsman

    Th3_Huntsman Senior Member Contributing Member

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    Yeah that way u can't do what I do and ruin the bike lol
     
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    Th3_Huntsman, Jul 3, 2015
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  6. Willrcr15

    Willrcr15 Well-Known Member

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    Willrcr15, Jul 3, 2015
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  7. Willrcr15

    Willrcr15 Well-Known Member

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    More of the same but on the exhaust side
    http://www.f1technical.net/forum/viewtopic.php?f=4&t=12772
    Weve got a titanium yoshi system on an ex race bike with resinators like that on each header pipe.
    The moral of the storey is to keep your air box's & exhausts air tight, especially the airbox
     
    Willrcr15, Jul 3, 2015
    #687
  8. Murdo

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

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    Jaguar cars did tests in the early 1950's on their C and D type racing cars and found that having an intake runner of 900mm long increased the horsepower from the engine by 20%. This was impractical of course as the Webber carbs were hanging out past the front wheel.
    I read today about the new Yamaha Tracer (3 cylinder 850cc) that has the three intake runners of 80mm, 102mm and 122mm to give the engine a greater spread of torque. Think how pod filters would stuff that up. :oops:

    The factories spend many hours and $$$ getting the intake and airbox correct for a particular engine to give its best performance, then for 'experts' to fit silly little pod filters (most of which cannot flow enough air because of their size) and wonder why their bike is slower and runs crap. :D
     
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    Murdo, Jul 3, 2015
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  9. Willrcr15

    Willrcr15 Well-Known Member

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    I like the sound of a 3 cyl 850 Yamaha, can't stop dreaming of a new H2 though.
     
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    Willrcr15, Jul 3, 2015
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  10. Murdo

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

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    Agree, I'd like to have a ride on one. Have to be a big step up from the XS750D I bought new in August 1977.
     
    Murdo, Jul 3, 2015
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  11. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Great article Will. Of course it is horribly complex with 4 cylinders pulsing into the resonator at the same time. I think any formula that would work would be far more complex than the example in the article, but one has to start somewhere. Most of us mortals just vary the bellmouth length, which works quite effectively, since we don't have much room to play with the airbox (resonator) volume. The paper referenced to by Bortoluzzi has two great animated gifs (worth a million words). Note the cylinder in the second version reaches the peak pressure (shown in red).


    [​IMG]

    [​IMG]
     
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    maelstrom, Jul 3, 2015
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  12. Joker

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

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    @Willrcr15 I stopped reading at "...Turbocharged engines can easily achieve a volumetric efficiency over 100%"

    Could have been right on the engineering afterwards but I didn't get that far, I was laughing too hard.

    Not only does it run at maximum possible efficiency, it actually creates efficiency while running! It's a progressive invention!! /sarcasm
     
    Joker, Jul 3, 2015
    #692
  13. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Put the rest of the plastic pieces on today. Fuel tap is leaking a lot less with better screws. Still have a little coolant leak out of the one the hoses to sort out, but running great. Grasshopper went for a test ride and noted how good the gearbox feels

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
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    Linkin, Jul 4, 2015
    #693
  14. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Started with idle circuit at 3 turns out. Still too lean. Another 1/4 turn out on all of them helped greatly. Carb #2 is the main carb, after adjusting it (naturally the hardest one to get to when the engine is hot enough to burn you) the bike is happy. Managed a warm start with no choke and no throttle.

     
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    Linkin, Jul 4, 2015
    #694
  15. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    .... and no 'hanging'

    :dance2:
     
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    GreyImport, Jul 4, 2015
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  16. Th3_Huntsman

    Th3_Huntsman Senior Member Contributing Member

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    sounds much better good job guys, still seems pretty hard to start though :S get to that fuel leak asap, i wouldnt recommend riding with a fuel leak.
     
    Th3_Huntsman, Jul 4, 2015
    #696
  17. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Just in case anyone missed it before the forum glitch, was fixing up the coolant hoses from rear of cylinder block to thermostat, and this happened...

    [​IMG]

    Now I can have that sorted as soon as Mr. Grey is back and can open up the shed. But I wanted to take the bike to Bunnings this Sunday... have to split the carbs and replace that little bugger, may need a re-sync and re-balance. Otherwise I'll quickly clean up the 3LN6 carbs and chuck them on for a comparison. The Yellow Peril won't be going anywhere for a while.

    CMS want 42.50 Euros for that fuel inlet. Madness. Can order from Japan for a lot less than that.
     
    Linkin, Jul 9, 2015
    #697
  18. Willrcr15

    Willrcr15 Well-Known Member

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    Interested to hear how a different set of carbies go as long as they are known to be in good order.
     
    Willrcr15, Jul 9, 2015
    #698
  19. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Well its a 3LN7 engine so it should be using 3LN6/7 carbies anyway.
     
    Linkin, Jul 9, 2015
    #699
  20. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Best solution would be to just split the carbs in the centre after getting the T piece from one of the spare sets

    If u do it carefully u may be able to keep the pairs togethers .... it wont change the sync unless u turn the sync screws

    Cable tie 1 and 2 together and 3 and 4 then take out the connecting rods
     
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    GreyImport, Jul 9, 2015
    #700
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