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Help Sprocket Choices for an FZR 250. (Kinda Urgent)

Discussion in 'Yamaha 250cc In-Line 4's' started by Revolver, Jan 28, 2016.

  1. Revolver

    Revolver Big Member Premium Member

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    My Bike:
    "Cherry" the 3ln3 FZR250
    So with the Willowbank Test and Tune on, I want to throw Cherry down the strip. But I Always wanted put new bigger rear sprocket before I did. And A Smaller Front.

    Right now, running 17 front, 55 rear.

    I want to go to 16 Front, 58 Rear if possible. 58 (or more) Only if I cant find a 16 for the front. Slipstream Performance only stocks up to 57t.

    Supersprox doesnt seem to sell to Oz directly.

    So In the interest of keeping things simple, does anyone know where I can get a 58t or bigger in a matter of days?

    So before Monday.

    Guess ill be on the phone alot tomorrow....

    Cheers for any points in the right direction.

    (And no a CBR 250 wont fit)
     
    Revolver, Jan 28, 2016
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  2. Joker

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

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    Sometimes wemoto can find stuff. Try them.
     
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    Joker, Jan 28, 2016
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  3. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Why dont you just go 13/14 on the front and a 57 on the back
     
    GreyImport, Jan 28, 2016
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  4. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    You might be better off with a 520 conversion. Better sprocket choices.
     
    Linkin, Jan 28, 2016
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  5. Revolver

    Revolver Big Member Premium Member

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    Cause Im pretty sure a 14 would be too small and cut into the chain guide. Or Spin off the sprocket.

    By Tuesday? Especially when I'm working each day.
     
    Revolver, Jan 28, 2016
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  6. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yea they carve into the guide ...... I just took a 15 off mine and it was ok with clearance.
     
    GreyImport, Jan 28, 2016
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  7. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Well 520 chains are the most popular, any decent bike shop should have them. Sprockets are another matter.

    The sprocket shafts on the 3LN3+ are longer, so you either need the proper sized 428 sprocket, which @maelstrom makes but is in Thailand, a 2mm spacing washer splined for the countershaft plus a standard aftermarket 428 sprocket, OR a 520 chain/sprocket conversion as you have a far wider variety of sprocket sizes available.

    15t/47t (with 106 links) is a pretty standard setup for a 520 chain & sprocket. It's what the Ninja 250R's use. A common change is is to drop one tooth on the front sprocket and add one on the rear. You gain acceleration but lose top speed.

    Another common change is just +1 tooth on the rear sprocket for slightly lower RPM at any given speed.


    But since the FZR runs a 428 chain as standard, you will see slight horsepower and torque loss as the 520 chain and sprockets are heavier. Every bit counts on a small displacement bike.

    Getting anything larger than a 57t in a 428 is impossible, no one makes them.

    Also http://www.gearingcommander.com/

    Standard 17/57 setup on 428 gives you a theoretical top speed of 185KM/h

    A 15/47 setup has a theoretical top speed of 198KM/h

    Don't believe it accounts for the weight difference though, and only goes up to 16,000RPM on the graph/tables
     
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    Last edited: Jan 28, 2016
    Linkin, Jan 28, 2016
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  8. Revolver

    Revolver Big Member Premium Member

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    My Bike:
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    Problem is I am Time limited and really want to just change sprockets.

    I know all about gearing commander, that's how I came up with the 16/58 combo. I want to be running out of breath just after the traps if possible.

    I think you may mean to go down 1 tooth on the rear to reduce RPM. That's how I sorted my current gearing. as going down one on the front increases RPM at any speed. Original is 56t but thats no longer available.

    Im not so sure on the 3ln3 onwards sprocket is applicable to my bike. I put a normal FZR one on and it works not a problem. No play, no wiggle, chain is straight as a die.

    But it has 3ln3 carbs on it.

    Im pretty sure its not the original engine. Being that the number is stamped at the front of the block, and nothing on top.

    Mine is the second from the bottom:

    http://2fiftycc.com/index.php?threa...0-3ln-bodywork-frame-engine-carburetors.3469/

    However has an external oil filter.... So its got to be a 3ln3 > engine. Its just confusing.

    Anyway, I might try for the 15t front sprocket. Though I didn't really want to change it.

    Any Dangers using a new sprocket on an old chain? Being that im only using it for one night, and both chain and sprockets have life left in them. At least another 5-10,000ks.
     
    Revolver, Jan 29, 2016
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  9. Th3_Huntsman

    Th3_Huntsman Senior Member Contributing Member

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    I beleive i read somewhere it is good to have an odd and even accross both sprockets as the chain lies on better. Just fyi something to look for
     
    Th3_Huntsman, Jan 29, 2016
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  10. Revolver

    Revolver Big Member Premium Member

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    Well Ive been running 17-55 with no issues.
     
    Revolver, Jan 29, 2016
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  11. Murdo

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

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    The odd numbered teeth sprockets are better for spreading the wear as you don't get the inner/outer link wear pattern from the chain. Sometimes the one you want is an even number, so just use it and don't worry.
     
    Murdo, Jan 29, 2016
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  12. Revolver

    Revolver Big Member Premium Member

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    My Bike:
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    Bought the 15t Sprocket today. Fit it up over the weekend.
     
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    Revolver, Jan 29, 2016
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  13. Revolver

    Revolver Big Member Premium Member

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    My Bike:
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    Fitted the 15t sprocket and she has a snappier throttle now. And every thing is not a gear up from what it is usually.

    So a 2nd gear corner is now 3rd & so on.

    And at 100ks, well it needs another gear. I don't know who many times I clicked 7th gear on the way in to work today. And I'll probably be searching for 7th on the way back out!

    The 17t sprocket goes back on Friday morning.

    Without.

    A.

    Doubt.
     
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    Revolver, Feb 2, 2016
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  14. driftwood

    driftwood Well-Known Member

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    • Informative Informative x 1
    driftwood, Mar 14, 2023
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