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Pinned C/Shaft Sprocket for FZR 3LN3-5-6-7 & Zeal

Discussion in 'Yamaha 250cc In-Line 4's' started by maelstrom, Jan 18, 2015.

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  1. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Obviously we cant know about other situations but to me its also obvious that everyone has most likely used the 520 kit as a solution....as was the case with the 2 bikes here

    The only reasonable answer in your case is your motor has been replaced by a 3LN1 or when it was built it they may have used leftover 3LN1 motors on the assembly line then used new designed and built ones

    Wats your engine number? @Revolver

    You don't have a problem ..... but we do.

    And we arnt alone as I have already posted ....

    http://www.kiwibiker.co.nz/forums/archive/index.php/t-151864.html
     
    Last edited: Jan 21, 2015
    GreyImport, Jan 21, 2015
    #41
  2. Joker

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

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    To Revolver's point I wonder what the extent of the problem actually is. Are we perceiving a problem or is there actually a problem?

    As I mentioned, I had the OEM sprocket but I undid the bolt with my finger (no tools required) after flattening the lock washer - suggesting it was never "tight" to begin with.

    Are we sure it's meant to be tight? perhaps the dynamic loading with the potential for 2mm of "quiver" isn't enough to see catastrophic failure of these parts?

    You would think that someone like JT sprockets have done some level of engineering on their design - they have to by law - to ensure the difference between theirs and the OEM is not going to cause problems. If they didn't then they're putting people in danger and that's a massive liability for them...
     
    Joker, Jan 21, 2015
    #42
  3. kiffsta

    kiffsta Senior Member

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    has anyone spoken to Dave @ fzr250.com , Im sure he would be in the know.
     
    kiffsta, Jan 21, 2015
    #43
  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    @Stu yes it is meant to be tight. Please consult your manual and I am sure you will find a recommended torque setting. It is not a floating sprocket design.

    It is obvious by looking at the comparison between gearbox shaft images supplied by Mr Grey, that the later model sprocket must be thicker. Various owners have confirmed this and supplied images of the thicker sprocket. The purpose of the thread is to define the correct sprocket and to see if one can be sourced or consider the options.

    3LN1 Shaft
    [​IMG]

    3LN3 Shaft
    [​IMG]
    As mentioned before the later models use a different shaft (same as the 250 Zeal) and the parts book confirms this.
     
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    maelstrom, Jan 21, 2015
    #44
  5. Joker

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

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    I'm not saying anybody is wrong - I'm simply saying that although it may have not been a floating sprocket as OEM that doesn't necessarily mean it can't be.

    The Japanese were always ultra conservative in design, and still are. Their Mtf (mean time to failure) under dynamic loading with their safety factors are likely to be higher than the standard engineering practises of today. That doesn't make either wrong or right, as long as the sprocket performs in it's current setup to the expected life of the part.

    There are many instances of aftermarket designs where things are slightly different. That is not to say the original design was wrong or right, it is saying that the aftermarket design is sufficient for the purpose although not exactly the same as the original.

    Food for thought anyway, I am interested to know the outcome either way.
     
    Joker, Jan 21, 2015
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  6. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    A 'floating' piece of steel with points on it rotating at 18000RPM within inches of my left foot doesn't sound all that great to me.

    :dance2:
     
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    GreyImport, Jan 21, 2015
    #46
  7. Joker

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

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    Well, my mech eng days have seen plenty worse - at least this one has a solid guard in front of it so your toes are likely to stay attached! I'd be more worried about what the chain would do in the event of a failure ;)
     
    Joker, Jan 21, 2015
    #47
  8. kiffsta

    kiffsta Senior Member

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    Got this from Dave @ fzr250.com

    HI Chris
    Had a look at the part numbers for all 2KR and 3LN

    Front
    All FZR have 1YL17460-00 17 teeth and a 428 chain

    Rear
    2KR 1HX25455-20-35
    3LN1 1HX25456-20-333LN3 1HX25456-21
    3LN5,6,7 3LN25456-40
    All have 56 teeth.

    Hope that helps.
    Have heard of a lot of 3ln with 520 chain though.

    Cheers
    Dave
     
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    kiffsta, Jan 21, 2015
    #48
  9. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Looks like someone at Yamaha did a dodgy. Shaft has changed, sprocket has changed, part numbers the same???

    We need to get in contact with Yamaha I think. Surely someone must have an answer. Are we missing a spacer item that's not listed? Are the sprockets wrong?

    After all with the age of these bikes it's hard to tell
     
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    Linkin, Jan 21, 2015
    #49
  10. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Just to add to @maelstrom post if you look closely at part # 24 in the 2 photos above then its taller in the 3LN1 ..... now to me the distance between the bearing/seal face to the tip of the shaft is the same for both (cant check that right now).... its the height (or how far its sits externally ) of # 24 that exposes the amount of splined shaft where the sprocket sits.
    The part # for 24 is the same across all models so I would assume its the design of the shaft , not its length, that has changed.

    Shaft parts.jpg

    I rest my case
     
    Last edited: Jan 21, 2015
    GreyImport, Jan 21, 2015
    #50
  11. Murdo

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

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    My thoughts are that the factory may have changed the width/length of the shaft/spacer to gain more surface area on the splines to slow the wear, and make it stronger. Or they could be using the different parts to save cost on commonality of parts. Either way, the fix would be to use the thinner sprocket and a 2mm spacer.
    The 520 conversion seems a dodgy/cheapskate way out of the problem (although it may last longer).
     
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    Murdo, Jan 22, 2015
    #51
  12. Joker

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

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    Yeh I'm actually going to put two lock nuts (one flattened) on the outside face of the front sprocket and see how it goes as I considered that the lowest risk (and cheapest way) to tighten it up. I'll post up results when i get them in, unfortunately had to order from JP.
     
    Joker, Jan 22, 2015
    #52
  13. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Well so far we can concur that:
    1/ The later models have a thicker sprocket.
    2/ The spline dimensions of the sprocket in question are known and very common across multiple brands and models.
    3/ Fitting a 520 conversion may be a solution - chain will weigh a bit more but greater longevity of sprockets and chain

    I emailed some sprocket manufacturers here but most Thai businesses never respond to emails. In any case, until someone accurately measures the thickness of the genuine sprocket there cannot be much more progress. Mr Grey said it was approximately 9mm and the NZ forum poster said approx 9.5 mm. Does anyone have a vernier/micrometer and a sprocket?
     
    maelstrom, Jan 22, 2015
    #53
  14. TechHeadFred

    TechHeadFred Well-Known Member

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    I have a set of vernier calipers but no similar sprocket.
     
    TechHeadFred, Jan 22, 2015
    #54
  15. Joker

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

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    I have a sprocket, I can do a measurement at work with a vernier or something. I'll try to do it tomorrow.
     
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    Joker, Jan 22, 2015
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  16. HiveFleetAbyss

    HiveFleetAbyss Active Member

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    I've actually just had to hunt down sprockets for my Zeal apparently no one does a 17 tooth aftermarket sprocket only go up to 16 which is fine for a FZR but the zeals factory from what i can find were a F17 R57 and a 428 chain with the 520 conversion being a F13 R44 and 520 chain, mine currently has the 520 conversion and it has the same lip as the example up above.

    Had to buy a genuine front sprocket so will measure it up when it comes in, almsot positive the output shaft for the Zeal and FZR are identical, will take photos just before I put sprockets on.
     
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    HiveFleetAbyss, Jan 22, 2015
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  17. HiveFleetAbyss

    HiveFleetAbyss Active Member

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    This is off a Zeal (3YX) motor and yeah that drives meant to be much further out.

    20150122_162049_resized.jpg

    As for front sprockets this is the 520 conv (13 tooth) front sprocket details are the exact same as this except apparently only 9.14 thick which might explain the tyre chain rubber not being that extra .85mm thick. But yeah FZR and FZX share same front, FZR's had one less tooth in the rear.

    jtf410.jpg

    20150122_162202_resized.jpg 20150122_162208_resized.jpg
     
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    HiveFleetAbyss, Jan 22, 2015
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  18. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    @HiveFleetAbyss good info.
    The 10mm one is just off some bike that uses something similar. I just showed it as being an example of something close.
     
    maelstrom, Jan 22, 2015
    #58
  19. HiveFleetAbyss

    HiveFleetAbyss Active Member

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    ahhhh.... all good then XD
     
    HiveFleetAbyss, Jan 22, 2015
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  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Is the original Zeal sprocket 9.14mm thick also?
     
    maelstrom, Jan 22, 2015
    #60
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