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Project Tony's ZXR250s

Discussion in 'Your 250cc Projects' started by TonyZXR, Apr 28, 2018.

  1. TonyZXR

    TonyZXR Well-Known Member

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    Hahah this is just a street beater. Haven't done anything on the other bike lately . Took the bed sheet off it and I got sad when I realised it's been there 6 months with no progress. 100% will pressure wash the life out of the cases before assembly .

    Sent from my SM-N960F using Tapatalk
     
  2. Murdo

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

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    Looks fine to me.
     
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  3. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Maybe I should go via Sydney on my next Tamworth trip and give you a helping hand?
     
  4. TonyZXR

    TonyZXR Well-Known Member

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    If you like sanding sure haha .The fairing's aren't even that bad .They just have so much paint on them , from my experience with the C model sandblasting is a good option but I won't be able to fit the two sides in the sandblaster I have access to... And I need to get a few sticker remade which is also proving to be a task

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  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I was just comparing it with this one

    43684827588bd993bed9d450424dd4a5_m8a%252520%2525283%252529__70557.1474364080.1280.1280.jpg
     
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  6. TonyZXR

    TonyZXR Well-Known Member

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    Good point . Probably should've clarified I did that because I didn't want black on the bottom because of my laziness haha

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  7. TonyZXR

    TonyZXR Well-Known Member

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    And she's registered!

    20191031_215234.jpg
    20191031_215211.jpg

    Not finished yet though. The initial ride has revealed numerous issues with it mechanically. Carbs still need the idle screws wound out another 1/8 turn (Stupid me tuned it with the wideband when the engine wasn't fully warmed up, even after idling for 30 mins....) head stem bearings are too loose , clutch slips occasionally and the front brakes suck . Front forks also feel too soft even when adjusted firm so they probably need a rebuild. But it didn't break down so that's a plus haha.

    20191031_232258.jpg

    Also could someone with an undamaged C model please measure between these two point of the fairing bracket. Im pretty sure this one is bent too far
     
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  8. ShaneP

    ShaneP Well-Known Member

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    I measured 322mm on 2 bikes and 330mm on the other, measured from the bottom of the 2 rear bolt holes for the mirrors. I would suggest that they have all been crashed or dropped, but that is what mine are.
     
  9. TonyZXR

    TonyZXR Well-Known Member

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    Sooo . Got the front nose painted finally after many hours of frustrating repairs . If i told you it was the same nose as when i bought it no one would believe it .

    Still fighting carburettor issues aswell . Just rebuild them with one of @maelstrom 's (what a great product by the way) Don't think i have the ability to tune them correctly so a dyno session is probably needed.

    20191120_124556.jpg
    20191120_124614.jpg
     
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    Last edited: Dec 6, 2019
  10. ShaneP

    ShaneP Well-Known Member

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    Are all the float needles sealing off properly everytime? That the other issue I found with mine. Worn seats/needles can catch and the overflow on those carbies is the engine - bad design fault!
     
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  11. TonyZXR

    TonyZXR Well-Known Member

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    So after fighting clutch issues it's now running great . Amazing how much power it was losing due to slippage . As you can see the clutch steels have gotten pretty hot but are not warped luckily and the friction discs still looked perfect (pretty sure i contaminated them with the wrong oil a while ago) New walker friction discs and fresh oil greatly improved it but it would still slip at high rpm so back apart it came . The original clutch springs measured a bit short so I'm thinking they just sagged and were too weak. New ebc heavy duty springs are 15% stiffer than original (they measured at 80lbs and the original measured at 60lbs). Bought a new clutch cable for it aswell . Wow what a difference. Apart from a firmer clutch lever it's better in every way .

    20191118_112936.jpg 20191118_115103.jpg

    Pulled the carbs off once again and wound the pilots back in 1/8th of a turn . Runs pretty good now . I suspect it needs a valve adjustment aswell but not really willing to get into it right now .

    20191222_163430.jpg
    Nice ride through the national park ended in us being pulled over , heard us coming for over a km away and decided to lecture us for 15 min. Apparently noise = speeding
     
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  12. TonyZXR

    TonyZXR Well-Known Member

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    You are 100% correct sir , I hydrolocked it once probably 3 months ago and thought it was a speck of dirt holding the needle slightly open. Cleaned the carbs and reassembled. Then it happened again about a week later. Got it started and rode it then broke down 20mins away from home (killed the sparkplugs. Managed to limp it home and guess what it was the same carb overflowing again. So i ordered 4 needle and seat sets and replaced them (should've done that when I put a litetek kit in them, guess that bit me in arse didn't it) adjusted the floats and balanced the carbs , also wound the pilots in 1/8 of a turn and replaced the plugs with some cr8e's this time seeing as I mostly ride on slow suburban rodes. It now rides like an absolute dream , has the tiniest stutter on extremely light throttle and a slight stumble between 6-7000 rpm . I think another 1/8 of a turn in would fix that issue. Funny because that would mean standard settings even with an exhaust. Apart from that it's been trouble free riding which is a nice thing to have especially with a 28 year old fiddly bike.
    IMG_20200331_141103.jpg

    Fyi if anyones wondering, that's kawasaki green with less yellow in the mix. Looks alot nicer imo
     
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  13. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    I was never able to fully fix that flutter / stutter at about 7k RPM on my ZXR. I'd done the o-rings between each carb on the air lines / breathers and overhauled the carbs more than once. My remaining suspicions were the vacuum fuel tap and fresh air valve, which I never got around to deleting. It is an emissions doodad. My understanding is that it doesn't let fuel vapours from the carb bowls vent to the atmosphere, but also it allows atmospheric pressure into the carbs as needed. I wouldn't be surprised if it was the cause of the problem in the end.
     
  14. ShaneP

    ShaneP Well-Known Member

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    It could be a tuning issue. Ride it at the flutter point and try putting the choke on. If it improves, it is lean (maybe put an o-ring under the needle), if it worsens then it it is rich and you're up the creek! Good luck finding adjustable needles to suit, there'll be some, but getting the right profile will be a tough search. You could try milling down the slides where the needle sit a millimetre or 2.
     
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  15. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Saw where someone had an idea to mill their slide 3mm deeper on a Japanese ZXR site a while ago,
    they then fitted 6x .5mm shim's and tuned it from there
    I couldn't find a follow up post about it though.

    zxr250 slide.jpg
     
  16. TonyZXR

    TonyZXR Well-Known Member

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    Checked all of that when I first assembled it , Personally i think it's a good thing to have, even to the point of someone adding one to their A model. It does make the fuel not evaporate out of the bowls or go stale. My A model always stinks like fuel for ages after it's run, the c on the other hand doesn't at all. Also the A with its stock exhaust and jetting runs absolutely perfect.

    Doesn't the emulsion tube have a set length and diameter, I feel like bringing the needle down that much wouldn't be great ? Coming from Weber car carburetors to motorcycle cvs give me a headache, anyone wanna sponsor me some keihin fcrs :D
     
  17. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Doesn't the emulsion tube have a set length & diameter? I feel like bringing the needle down that much wouldn't be great

    Not that I know what I'm talking about, but I believe raising or lowering the needle in the emulsion tube changes the point at which the different holes in the emulsion tube start aerating the fuel mixture and the amount of fuel that is being aerated. The main jet and fuel level obviously effect this as well. The Keihin people put their "best" needle in there to cope with the characteristics of the engine those carbs are feeding. Mikuni let you raise and lower the needle to fine tune your setup. The only thing you could try with Keihin's is different needles. Their taper and angle of attack must correlate to the tune and revs of the engine they're put into. Lots of science in there me thinks. As Tony said, his ZXR250A runs great with standard jetting.
     
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    Last edited: Apr 21, 2020
  18. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    What @Frankster said. Moving needles up and down is just changing when things happen. Makes sense if you are moving your cam timing but otherwise I think you are barking up the wrong tree.

    Keyster have made tuning kits that include needles of different tapers.
    http://www.jp-stores.com/mc/we70630/?c=336
     
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  19. ShaneP

    ShaneP Well-Known Member

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    Moving the needle up and down changes the midrange tune, as does changing the spring for the diaphragm. If you've changed mufflers or intake or altitude or climate conditions, they may need adjusting. The standard muffler isn't a continuous tube, so an aftermarket one will move your tuning about. Air leaks in the exhaust can also mess with things.
     
  20. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    I think you're confusing 4-stroke engines with 2-stroke engines.
     
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