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GSXR250R (GJ73A) Race Bike Build

Discussion in 'Suzuki 250cc In-line 4's' started by Boydie77, Apr 22, 2014.

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  1. Frankster

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

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    Welcome.

    I too have one of these lovely bikes (actually, it's my wife's bike). I will be following your progress with interest.

    Cheers
     
    Frankster, Apr 24, 2014
    #21
  2. Frankster

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

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    Hey Simon,

    What city are you in?

    Frank
     
    Frankster, Apr 24, 2014
    #22
  3. Joker

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

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    Simon - you rock man. I'll look into that one closer now... I'm just hesitant to take a gamble on $ as I'm trying to keep my costs down.
     
    Joker, Apr 24, 2014
    #23
  4. Frankster

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

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    Simon, what are the differences in the pistons? My wife's bike is the 72a
     
    Frankster, Apr 24, 2014
    #24
  5. Boydie77

    Boydie77 Well-Known Member

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    Simon, you are wealth of information, top stuff dude! :cool:

    The 03-04 CBR600RR shock is exactly the same length - 310mm. All the bolt holes are the same size, just need the CBR lower shock bolt as it's slightly wider in the clevis. Its a straight drop in replacement but the igniter unit must be moved to accommodate it. I know what you mean about the soft spring, both the original and my RGV shock felt WAAAY too soft doing a bounce test. This shock was a bit too soft for my 90kgs in the CBR, with the lighter weight of the GJ73a I'm hoping it will be perfect. I have no idea if a 900RR shock will fit sorry.

    I measured up the VJ21 rear wheel, its near identical. The hub is about 3-4mm narrower on the disc side, I should be able to space it out with washers to get it aligned. Hopefully the stock spacer will work but shouldn't be too hard to get another one made if needed. A major bummer they are an 18" rear, tire choice will be pretty much limited to Dunlop GPR70's and wets are non existent in this size apparently. One of the guys who races a ZXR has made his own wet / intermediate by grooving out a GPR70! It hasn't rained at a track day or race down here for ages so he hasn't had a chance to test it out yet, but it looks impressive for a DIY job! Doubt my tire warmer will fit either but I have a plan for that...

    Front VJ21 wheel has same disc size and spacing so it's looking good as a spare. Front forks are very similar, I'm hoping I can use the VJ21 triple clamps as they are a bit beefier with a double pinch bolt lower. Will also use the RGV clipons as they sit a lot lower. ANZAC day tomorrow so hopefully will get plenty of good workshop time in! :)
    WP_000958.jpg
     
    • Like Like x 1
    Boydie77, Apr 25, 2014
    #25
  6. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Frank I'm based in the uk :(..North Wales to be exact but I shouldn't moan..good (read dry!) weather this weekend so a blast or two might be the order of the day!! Just seen your Gsxr GJ 72A..I had the exact bike when it was a year old..same colour scheme 1988 model year!! Its quite hard to explain the differences in pistons but I've got a few 72a pistons here so will send you a picture next to a 73a one..the main difference is the recess in the centre of the piston for the plug being elongated and deeper in shape..the 73a bikes run cr9e/cr8e plugs and yours are shorter in thread..factory plugs are C6HA,C7HA,L8A or the ND equivalent U20 FS-U, U22FS-U or U24FS-C for the 72a..basically the 'screw thread' part of the plug is a lot shorter..I've got a full w/shop manual (in Japanese) for your bike and an english one for the motor if you want it - not sure how to send it as i'm not great with pc's but i shall do my best..ur bike will be running the bst 27 twin barrel carbs which is the main difference together with the more obvious cylinder head mounting points being different to yours on the 73a..overall performance is very similar though I couldn't get my 72a over the 37bhp mark as the ignition maps cams and timing are different..factory specs say they made 45bhp but I couldn't ever get mine close..then again it was all original and had done a healthy 113k kilometres when we parted..how I want that bike back!!!
     
    Simon, Apr 25, 2014
    #26
  7. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    ..73a on the left..72a on the right!!!
     

    Attached Files:

    Simon, Apr 25, 2014
    #27
  8. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Boydie,

    Not so bad on the information side yourself mate!!!..i'm going to start measuring up this weekend as its the only gripe I've got left..I've already enlisted the help of one of my old school mate aquantances who's just got married to a guy who work for harris engineering (ohlins) specialists here in the uk..front forks revalved re sprung and hopefully turned around within the next three weeks or so..im crossing everything my spare fireblade one is similar to the 600rr..minus the shock bolt - OEM stuff here is usually a week or so plus an ordering fee :(..im getting impatient!! RGV clip ons a good idea me thinks but I reckon you like your bikes a bit flighty..I'd say i'm a fast road rider but track days have taught me the bike turns in fast enough but im getting on in years now and the kids are still a bit to young to go mental and gung ho like I used to so it could be im turning into a wuss lol!! The 18 inch rear and tyre choice..what ever possessed Suzuki to go there beggars belief!!!!!! I'd be interested to hear more on the tyre warmer route lol..I can get the pegs down and the sliders are mildly scuffed but that's my lot!!!! Megga interested in your build and picked up another (that makes several now...misses is telling me we need the garage back!!!) engine last weekend..2100kms from new..i shall take a quick pic and let yus know if I can get the little beggar to make any more than the best I can currently get!!!

    Keep the posts coming boss,

    Cheers si
     
    Simon, Apr 25, 2014
    #28
  9. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Got pretty much the whole bike less fairing for £300 with history from 1991..dry stored since 1992..gumtree you are loved..and bless the people who dont value what they've got!!!!!!!!
     

    Attached Files:

    Simon, Apr 25, 2014
    #29
  10. Frankster

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

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    Thanks Simon. I don't think my (wife's) bike makes more than 37hp either. I've ridden it many times and prefer my ZXR for sheer grunt (if you can say that about a 250!). The GSXR handles better and "feels" smaller that the ZXR. I would love a workshop manual. We're lucky to have STU on this site (he reads Japanese) so Japanese manuals shouldn't be too much of a problem (for Stu).

    Cheers

    Frank
     
    Frankster, Apr 25, 2014
    #30
  11. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Frank,

    Im just shooting off to work but try these (if they upload!)..STU reads Japanese :):):):)..speak soon!!

    Cheers
    Si
     
    Simon, Apr 25, 2014
    #31
  12. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    ..file too large..if someone can explain how to send stuff then its all here..sos for being a bit slow on computers!!

    Si
     
    Simon, Apr 25, 2014
    #32
  13. Boydie77

    Boydie77 Well-Known Member

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    Simon, the easiest way to share the manual would be via a cloud storage service. I would suggest creating a Microsoft Onedrive account, it's free and you get 7GB of storage to use. Then is just a matter of creating a folder, uploading the file/s and click the Share button. This will create a link you can send to people so they can access the file. You could post the link here but probably best to send via PM to those who want it, which should avoid any copyright issues as I'm not sure what the website's policy is on sharing such documents...

    Create an account here:
    https://onedrive.live.com/
     
    Boydie77, Apr 25, 2014
    #33
  14. Boydie77

    Boydie77 Well-Known Member

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    Hay and nice find with that engine! The GSXR's seem to be super rare here in Aus, but the Across was a good seller. The local wrecker has a couple & I was thinking about buying a spare engine. I read on here that the pickup coil is wired differently but do you know if there are any other differences?

    I made a bit more progress today. Scrubbed and cleaned a few of the ickiest parts, that being the sprocket cover / clutch lifter and basically the whole front end. Both sets of forks were filthy due to blown seals and covered in oily grime. Got it all stripped down and compared to the RGV parts. The wheel is exactly the same apart from the discs being 1mm wider and noticeably heavier without any holes. Triple clamps are the same dimensions so I fitted these, although also noticeably heavier so I will probably experiment with the lighter ones down the track. The VJ21 fork lowers are identical, bounce test says the springs are a bit stiffer and the caps are different with threaded preload adjusters not 3-step which is good. The length is shorter by about the height the GJ73 clipons mounts about the triple clamp. I didn't bother measuring precisely as I'll rebuild both fork sets and experiment with geometry and different settings.

    So still no major dramas with the project so far. I have found one braided brake line that will fit but my other spares are too short so have to add that to the shopping list.
    WP_000998.jpg WP_000996.jpg WP_001000.jpg
     
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    Boydie77, Apr 25, 2014
    #34
  15. Frankster

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

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    Si, how big is the file?
     
    Frankster, Apr 26, 2014
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  16. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Hiya mate,

    The file for your bike (72a) is 66,724 kb as a pdf (not sure what that is)..I've already got that one on a memory stick..if you send me your email address I could try and send it as an attachment?? will start scanning the 73a one in in a bit..also got other manuals which I'm not sure are on this site so one I can do one I'll do them all so we've all got them..:)

    Cheers si
     
    Simon, Apr 27, 2014
    #36
  17. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Hello guys...

    Right ten mins of playing around..Boydie I've just realised I've already got a cloud account as it went straight in when I clicked that link and said welcome simon lol..I've just uploaded the 72a information I have and will get my daughter to start scanning the 73a manual for tomorrows pocket money in a bit..guys this will cost me a fiver lol :)

    On another note my full factory 'as new' restoration is coming together..well apart at the bodyshop in work that is..pictures to follow...

    Cheers si
     
    Simon, Apr 27, 2014
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  18. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    Simon, Apr 27, 2014
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  19. Frankster

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

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    Frankster, Apr 27, 2014
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  20. Andy T

    Andy T Member

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    hello all,
    good to find some decent information on the baby gixxer at last.
    I bought one of these last year and have now started to get it back on the road.
    does anyone know where i can source a rear disc for a GJ73A. I,m guessing that its the same component as used on other models but which ones?
    cheers
    Andy
     
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    Andy T, Apr 29, 2014
    #40
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