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Project First bike, the FZR250 3LN

Discussion in 'Your 250cc Projects' started by I_b_pirate, Feb 17, 2020.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    BTW - this page has the pilot chamber bungs explained, basically you use a stanley knife blade under the edge to lever them up - be gentle as it's a weird sort of crumbly metal, almost plastic like in it's consistency - once you get them moving upwards you can go to blade screwdrivers

    https://www.2fiftycc.com/index.php?threads/fzr250-3ln3-carb-problem.8770/page-5#post-112020
     
  2. I_b_pirate

    I_b_pirate Member

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    Couldn't get any number, there is no compression. Even if the rings were kaput I'd still expect some compressin

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  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    That's not good at all, I recall those valve clearances were below minimum spec, it's either the clearances or bent valves if they cams were installed mis-timed at some stage

    Compression testers have a schrader valve like a tyre, is there a chance it was stuck closed, rubber stuck to the metal and unwilling to budge and needed a press to free it up?

    Oil down the plug holes next to test the rings

    Not sure what I'd do first, clearances or check for bent valves

    FWIW - the cylinder head isn't difficult to remove and new OEM gaskets are available for about ~$35 which isn't expensive

    IIRC correctly I got mine from these guys, express post - no issues - currently listed as available in Australia which is a good thing, so the local Yamaha dealer should be able to procure one for you

    http://www.firstclassmotorcycles.com.au/part/yamaha/3LN1118100#content
     
  4. I_b_pirate

    I_b_pirate Member

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    I'm pretty sure I'm the first to turn it over since the new valves were put in so I don't think they are bent, but I do think it has something to do with the intake cause it's blowing a fair amount out of those carbs.

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  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Well the cams have a small casting on them 'IN' and 'EX' - I suppose they could be in the wrong spots - on the RHS facing forwards between pots 1 & 2 from memory
     
  6. I_b_pirate

    I_b_pirate Member

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    Cylinder 1 cam lobes are pointing inward, I hope that's right. Actually I hope that's wrong so it would explain everything.

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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Well with cylinder 1 firing that cam should be pointing outwards as it's just inhaled and should be preparing for the exhaust to open, so that cam should be preparing to push down on the valves

    Not sure if the valves can clash, but they won't be bent as the timing itself if correct, just the wrong valves moving - it's been firing a spark at the point where the valves are both just sneaking open during the overlap point between exhaust stroke and intake

    I don't think they will be bent, and it pretty much explains everything you've been experiencing, and it's a quick fix
     
  8. I_b_pirate

    I_b_pirate Member

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    Ahhh I'm excited to get home now haha, but still gotta pick up new plugs

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  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK just looked at this pic - those cams are in the wrong place, those lobes for cylinder 1 intake are for the upcoming exhaust stroke on that cylinder - now that I think about it, the 'IN' and 'EX' are cast between two cam lobes.

    Just swap them and then check the clearances and it should go VROOM
     
  10. I_b_pirate

    I_b_pirate Member

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    And we have a running fzr 250! She's a little rough, gotta tweak the timing and gotta sort a few coolant leaks before I can run it warm but she runs! And that's a huge milestone for me. So many weeks of tinkering and it all came down to the cam shafts being the wrong way.

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  11. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    So glad for you, no wonder it was a total mystery

    Do the seals in the carbs and you've actually been across many of the settings, fuel level is most important, then you have the balance and pilot screw adjustment which usually happens in tandem
     
  12. I_b_pirate

    I_b_pirate Member

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    There's a fair amount of tapping but it hasn't had oil through it in a decade and the longer I ran it the better it was but the water pump is leaking so didn't want to run it too long

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  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    The rest is easy, it's checking things mostly EXUP valve, balance carbs and adjust pilot screw, I forget if there's a gasket underneath the water pump, if there is, you can buy gasket paper and cut your own, it's always a god thing to have to hand anyway - comes in various thicknesses

    If the coolant has been sitting all of that time, worth changing and you can put a portion of vinegar ~25% in distilled water to run through as a flush
    One thing important to know is that there are two coolant system bleed screws on the cylinders to get residual air out.
     
  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  15. I_b_pirate

    I_b_pirate Member

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    Unfortunately I don't think I'll be ordering parts from over seas anytime soon. It's coming from the seal behind the water pump, I've got some gasket maker which worked on the outer seal so I might do some cooling system botch jobs tonight just to get it holding water. It's had no water in it since it was pulled apart 10 years ago. I did put a video up on YouTube
     
  16. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Coolant drain head.jpg
     
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  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Surprised it ran at all without the airbox, with that in place I think you'll find it's much smoother

    For what it's worth the transmissions make a lot of noise also, they sound like a bag of spanners but that's normal - likely a big part of the noise you are hearing
     
  18. I_b_pirate

    I_b_pirate Member

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    Ok I'll get the cooling system sorted and get it warm and see how it goes, might throw some fresh oil and new filter in her too. I reckon the run would have freed up any **** that's been sitting in the channels

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  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    It might be sufficient to remove the water pump cover and gently clean the mating surfaces then reassemble
     
  20. I_b_pirate

    I_b_pirate Member

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    It was leaking from the o ring behind the water pump, I just clean it all up good and slapped some gasket maker on it. It will work for now and I'll replace the ring later. The air box rubbers must have shrunk tho cause they don't fit on the carbs or in the air box properly and the filter I have to get ordered in and will cost about $100 so I'm wondering if I should throw some pods and retro fit the box to them

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