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Project Yamaha SRX 250 3WP

Discussion in 'Your 250cc Projects' started by Andych, Oct 9, 2016.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Interesting on that XS650, unless the pad does correctly cover the swept area of the disc with that rear piston located there, I can see no reason why they didn't shift the lower mounting hole for the caliper inwards

    Those fork lugs must have been tapped/helicoiled also, which is a good option as it avoids Z shaped caliper adapters

    Is there a fork leg lower which has the same diameter chrome stanchion as the SRX, 100mm lug spacing and the larger rotor diameter that you desire?
     
  2. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Most of those guys are using 289mm disc rotors (FZR250?) and the pad contact area of the rotor is about 10mm too small for the Blue / Gold spot caliper. Having said that, they could still have made it a better fit than it is.
    He is using Nylock nuts on the back which doesnt protrude past the caliper so it misses the rim.
    FazerCaliperTop.jpeg


    Somebody else did this one... same principle but I like the design a little better (not quite as chuncky) but still not positioned right. IMG_0814.jpeg



    I am not sure what other Yamaha uses 33mm diameter forks and I doubt they would have the latter 100mm spacing anyway.
    Once I have the front end available Iwill be able to see how it all fits together.
     
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  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    FZR250 is 282mm diameter rotors, I think you're correct on the fork tube diameter and the 100mm spacing on the caliper lugs, even the 1989 TZ250 I looked at had 83mm spacing for the caliper lugs and 282mm discs

    FWIW - there may be pads with a shorter [not as high] contact patch which fit the monoblock calipers - think of some of the newer Yamahas that have the monoblock calipers - I'm thinking perhaps XJ6 and FZ6 or perhaps even an MT07 [which I know for a fact has monoblock calipers - they're all equipped with dual front discs, those discs might not be as high in the contact patch
     
  4. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Trust me... I have looked at pretty much every option...lol
    The monoblock calipers wont be an issue even with the standard pads as long as the offset on the FZR600 discs I have works.
    they are the right size so would be fine... I am thinking though that the standard FZR250 3LN disc and caliper may just work as the distance from the axle to the mounting holes is the same on the SRX forks... if that is the case it will only be the offset that needs to be adapted. I am not even sure of the SRX disc diameter.
    I am now just going to wait until I have all the bits and then it will be easier than trying to find info that is for the most part not available...
     
  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    AMEN to that, I concur, trying to find details on many measurements can be a quest to rival that for the Holy Grail...
     
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  6. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    I had one last little brainwave... the SRX250 3WP uses basically an FZR250 3LN front wheel but only single disc... so I looked up the part number and it comes back as the same as for a TZR125 1991 front disc (2TV-25821-01-00).
    As far as I can find this is a 320mm front disc with the correct internal diameter and 10mm offset. Could it be that simple?
    I dont want to use the 3WP dual opposed piston caliper but if it is the same dimensionally with regard to centre pad distance from the mounting holes... then it will be a piece of cake... but it probably wont be...lol
    I am out of here... I have a 12 hr drive tomorrow... before I start work.
     
  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    2KR front wheel/disc suitable?
    Single disc, 320mm, I don't know the rim width for certain though

    Happy travels...
     
  8. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Happy travels??? If only. I managed to severely injure a poor innocent Hyundai Santa Fe.
    Apparently large loose rocks hiding on the edge of wheel ruts do a fair amount of damage to prop shaft, centre bearing exhaust etc ( I gave up at that point) to Korean SUV’s

    As for a 2KR wheel, nah, I already have a perfectly good 3LN wheel and even if I need to change the disc the TZR will bolt straight on.

    Next job in the short term is to find a tow hitch for the Range Rover. The Hyundai was my tow vehicle to get the SRX home.


    Sent from my iPhone using Tapatalk Pro
     
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  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    2KR front disc rotor will be 320mm and bolts onto the 3LN front wheel, that's why I mentioned it, but if you've already got a TZR 320mm front disc then all good

    Bummer about the rock damage
     
  10. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    I dont have either... I will wait till I can get all the parts together and measure up what I need... I amnot sure of the offset for the 2KR disk as it uses a different caliper to all the others... so it is just a waiting exercise now... and then I have to find a way to get the SRX back here from the Storage shed as the Hyundai wont be fixed for a while, once they quote it and then sort parts etc.
    Its all good fun, lucky it wasnt far from Tamworth that it happened and @GreyImport was able to play taxi and drop me at the airport so I could get home... :)
     
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  11. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Well my SRX parts from Zenmarket are in the Country... DHL says I will see them by the 18th... wonderful... lol
     
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  12. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Hopefully the final parts (from Japan at least) tosort out my revised braking have arrived at Zenmarket, I had to change the shipping company from DHL to UPS as it was going to cost A$70 more to send the package via DHL.
    It is an SRX250 front wheel and axle. Then I will have a choice of FZR250 front disc, FZR600 front disc or a 320mm front disc from several sources... FZR250 2KR, SRX600, Aprillia etc... it is just figuring out the easiest way to do it to make it look as Factory as possible while employing either the Gold Spot caliper I have or selling them and getting a Brembo caliper from the Aprillia RS250 or similar.
    So many options... I will wait till the wheel arrives and then measure it all up from there.. still watching youtube to learn Fusion360 lol
     
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  13. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Well I have been playing with Fusion360 as well as looking at differente Caliper brackets.
    My thinking is to mount the bracket as a normal Caliper would mount (with M10 threaded holes) and then offset the top section to allow for the caliper to sit in the correct position and offset (hopefully) to suit the applicable brake rotor.
    This is my first cumbersome attempt at said bracket... I got the extrusion a bit wrong and the top mount isnt the right shape but I was really just experimenting a little... Once the 3WP wheel arrives and I can mount up a disc etc and get some proper refence points I will hopefully be a bit better at it. Once I am happy with it I will get it 3D printed to prove the concept etc. Trial run bracket v2.png

    Similar concept to this....
    6EA8A35F-878A-4E53-A54F-E159C9C77C16.jpeg
     
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  14. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Yours looks very good because you've followed the contours of the fork lugs which means it will be rock solid against the fork structure

    The one you have pictured as an example looks well designed also because it position the caliper with it's sweep towards the upper fork lug, that way everything is basically in tension when you apply the brakes with the force being directed towards the fork lug mounting point
     
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  15. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Yes, the Brembo caliper and XS650 fork allow that to happen... the Brembo is a 40mm mounting and the XS650 has 112 mm lug centreline on the fork.
    The SRX has the 83mm mounting so the top mount is lower down and with 100mm on the gold Spot caliper it will place the top Caliper mount quite a bit higher.
    This can potentially be offset somewhat by using the FZR600 disc which is a 300mm diameter. That at least takes 10mm out of that distance.
    I still have a long way to go with Fusion360... for some reason I cant go back into the sketches and change things. I may end up having to start over but you only get to have 10 saved designs in the "hobbiest" free version so I need to be mindful of that.
    There are plenty of good tutorials on youTube though so hopefully I will get to a point where I am happy with the design. I have a hand drawn sketch with measurements that I am working from. I dont trust my memory these days lol
     
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  16. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    So I was playing around more tonight... With Fusion360 you can take a photo of an item then use it as a background to sketch around it... after you have calibrated it to be the correct size.
    So I have a pic of the caliper and I removed all the background... then added it in and calibrated it...
    I will use it to sketch a new bracket from as I cant seem to change the existing one (probably something I did) to match the caliper features. It does show roughly how it will look.
    I also have a picture of the fork leg so I will remove the background on that as well... then I might be able to map it all out in digital first.
    Trial run bracket v3.png

    I just had to paly a little more... this is with the Fork leg calibrated in... I have added the dimension of the SRX250 3WP Disc (320mm) and the position of the caliper is a little off... so plenty more playtime to get it all correct but it is looking promising.

    Trial run bracket v4.png
     
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    Last edited: Feb 25, 2022
  17. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    Well my SRX250 3WP 17" rim arrived today and I have to say I am pretty happy with it... no dings. or chunks out of it... it spins true on the wheel stand... all good news.
    The downside is I will need to do a fair bit of poilishing to bring it up close the FZR rim but I can handle that... fist step is to sort the brakes.
    I couldnt resist plonking it and the fork etc on the workbench to see how it all lined up.
    I put the FZR250 3LN disc on for reference and was pleased to see that the caliper wont foul on the rim at all.. and it would pretty much work with that disc but the bracket would be a lot bigger than with a larger disc.
    Measuring the critical points the FZR25 disc will have it back quite a bit as the bottom caliper mount would be inline with the lower lug on the fork.
    The FZR600 disc is 300mm dia so 10mm more than the 250 and that would take the caliper closer to the fork bubt still not ideal.
    If I get an FZR250 2KR disc (anyone got a good 2nd hand spare one) that is 320mm and I think the same offset as the 3LN (9.5mm) then the caliper should pretty much sit as shown in the pic below. And that would be a good end result I think.
    If all else fails there are other Yamaha 320mm discs that I can use.
    Pity I will be away for the rest of the week... otherwise I could play some more with Fusion360 :)

    IMG_6455.jpeg
     
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  18. Andych

    Andych Moderator Staff Member Premium Member Contributing Member

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    On further inspection it appears the same disc is used on FZR250 2KR, TZR125 RR, TZR250, Aprillia (several models) and the SRX250 3WP.
    320mm x 10mm offset with the 64mm id. I am guessing that will be my ideal choice... the search begins :)
     
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  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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  20. James P

    James P Active Member

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    Andy,

    If you are using a 3WP front wheel with the original SRX forks, you should effectively have the same set-up as the SDR200 (2TV). When I built my SDR a few years ago, I used a Ducati Monster 695 front disc (300mm) from Metalgear with a 3LN caliper. I'm not sure if any of these parts will suit your purpose, but here is some info: http://diffrentstrokers.com/phpBB2/viewtopic.php?t=1983

    Regards,
    James
     
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