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Suzuki GSX-R 750 M (1991)

Discussion in 'My Bike' started by supamodel, Dec 21, 2009.

  1. vinniebarbarino
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    vinniebarbarino Member

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    Anthropomorphism I know, but I think motorcycles can tell when you're about to "go pyro" on them.
    Been at that point myself.
     
  2. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Well, I got to use MOAR FIEREREE on it last night.

    Not cause it was broken, but so I have an exhaust hanger for Marulan. Had prototyped one out of the Mechano looking stuff from Bunnings, was time to build one from something a bit more substantial so that it held up to the vibrations. See, I've removed the pillion pegs; on these gixxers that means no exhaust hanger.

    I used fire cause I had some uber thick strap steel here. Blowtorch makes it nice and malleable. May have quenched it a bit much after so it might be a bit brittle but it'll last one day at the track... I hope.

    Other than that: single seat tails for these gixxers are hard to find. I have a fibreglass copy of a 1989 GSX-R 750R tail... it requires a bit of editing of the subframe to make it fit:
    * Seat mount needs to be substantially cut apart. I have left a relict seat mount; it'll be possible to re-mount the stuff & either get it welded or bolted on if I want to make it stock again.
    DONE!
    * End of the subframe needs cutting at about a 60 degree angle so it doesn't foul on the back of the tail.
    DONE!
    * Mounts need to be constructed between the top and bottom arms of the subframe right up where the battery box is.
    RHS DONE!
    * Reinforcement of the fibreglass seat so that it sits on the top of the battery box.
    * Strap between left and right sides of the subframe to act as the rear brace for the seat.

    But it progresses.

    (It also still starts).
     
  3. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Well, this project stalled for a while.

    The more it's progressed to a track bike, the more bugs have crept in.

    Time to return it to the road. Need to build a wiring harness cause it's falling apart, fix a few things in the subframe, and get a rego inspection. Then ride it and when I'm sick of filling it with oil, do the valve stem seals.

    Gets me a junior old dunger on the road too.
     
  4. Gosling1
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    Gosling1 Forum Whore of Death Veteran Member Supporter

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    whatever happened to Vinnie ??

    nice work on getting the gixxer going again mate, it is more of an apprentice dunger really :biggrin
     
  5. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Don't short out race lithium batteries.

    Pretty sparks though.
     
  6. Gosling1
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    Gosling1 Forum Whore of Death Veteran Member Supporter

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    oh noes !!!
     
  7. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    I pulled it out to charge it - it's actually sat for a year and it still cranked the bike, just a touch slowly. Still about 12.4V, which was nice.

    I decided instead of doing it right and picking up a second anderson plug, I'd just hook the alligator clips of the battery charger to the terminals in the anderson plug connected to the battery. There's just enough room to do this without shorting it out. Just enough. Only if you're not a retard and pay full attention.

    Hooked up one alligator clip, all good. Wriggled the other one to try to connect it to the other terminal in the anderson plug and KAZAAAAAAP. Awesome sparks and awesome noise. Battery charger decided to crack the shits for 10 mins (as it's a shit auto sensing one) but it came good and took a charge.

    Might go see if it'll start again. I think I rectified a dodgy earth which was one reason it wasn't running properly, though I'm still suss that the reg/rect is poop. And given it's internal to the alternator, I fear there is some airbox cocking around in my future...
     
  8. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Why you trust your tuner: gixxer hasn't started very well since Marulan last March. Dyna module was rooted - replaced and it was better but still shit.

    Bought a set of CR9EK's (twin electrode goodies) from Brett in Jan. Stock they use CR10s but Brett goes a nine might be better. I first cleaned the stock plugs - no better.

    Put the 9s in and FMD it starts first crank even with year old vpower in the tank. #winning

    Now to find the road gear while also race prepping it with stuff like covers etc. It might make the 1 hour...
     
  9. Gosling1
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    Gosling1 Forum Whore of Death Veteran Member Supporter

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    well that sounds better all around.....
     
  10. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Bellypan is already off to work some fibreglass magic. 1989 GSXR750Rs didn't have fully enclosed bellypans. Stock headers would be fine to just box it in, but the yoshi full system on this protrudes a bit. Nothing MIZ's fibreglass magic can't sort this week & cure over easter.

    Meanwhile, I started getting it back to 1991 road spec. I think it needs a decent shakedown over winter. Plus I can practise my starts off the lights.
     
  11. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    [​IMG]

    Racers Edge fairings for this particular gixxer don't come with a fully enclosed bellypan. I have seen many 'interesting' nappies on gixxers all under the guise "too hard to make the race fairings work with the headers". With some flexible cutting board, lots of gaffer tape, and about 2 hours of fairings off-make a bowl out of cutting board-fairings on-check clearance-fairings off-adjust-fairings on, check-have a beer-fairings off etc loops, I think my method will actually work.

    I needed to build them back about 25 mm so I have enough room to then make a back to the fairings so they will contain the > 3.5L the MoMS require.

    This is only the first step - about 3 layers everywhere of woven cloth, strips to reinforce, plus a fair additional amount at the 'new' bit at the back for added strength. Compared to the RGV this is about 50x more complicated to get the shape right, though the fact the bellypan is already 1 piece does simplify matters a little -- easier to keep everything in alignment as it sets. We also did the RGV fairings from the outside whereas these are being done from the inside, so it should be a bit neater.
     
    Last edited: Apr 2, 2012
  12. MickLC
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    MickLC Member

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    So is the chopping board part of it or just a mould?
     
  13. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Just a mould. Flexible enough to let me get the right bend in it (including using some gaffer ribs to pull it a little bit to the left, as the collector box on the headers is a touch left of centre), yet strong enough to hold the resin in place.

    Waxed it with nice carnuba wax to make it releaseable. Same way we did the RGV fairings - one cutting board provided the headlight shape for that, and another lost its life to make the bellypan.
     
  14. MickLC
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    MickLC Member

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    Just checking, I was going to do something like that with the seat on the LC :up
     
  15. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    I need to cover a couple of similar bolts on the single seat for the gixxer and I'll take pics of how I intend to tackle it. Mostly clingwrap plus expanding foam - we're currently carving expanding foam to make a sexy rear cowl for the RGV - idea is to make it a shade too small, then bog it to the right dimensions minus the 1.5 mm that 3 layers of fibreglass seems to take up. Will make an excellent plug.

    I also should have a fair amount of spare modelling clay to cover up various bits on the LC if you need - bought another CF kit (this time blingy blue cf-kevlar) to make clutch etc covers for the gixxer, and I still have a heap of modelling clay from the RGV's clutch cover.
     
  16. MickLC
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    MickLC Member

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    No need for any fancy clay, it'll be under the seat foam so it just has to be reasonably flat on top and it can look like all sorts of arse underneath....not that it will, but the option is there ;)
     
  17. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Main reason for the clay is just to mould around stuff like bolts, not to stop it looking like arse. I'm generally happy if the fibreglass holds, looks are secondary. I'm always pleasantly surprised when they look ok, too.
     
  18. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Long post but it's my thread and I like to keep it as a bit of a journal of where I'm at.

    Pulled the cam cover off a while ago. Cams are nasty looking - chrome flaking off etc etc. Well, there goes the easy choice of just lifting the cams and doing valve stem seals without pulling the head (need to do valve stem seals cause it is pouring oil into the #3 cylinder, fouling that plug with oil, then making it run like arse, fouling the other plugs).

    Those who don't know their GSX-R 750 history, the 1991 is a bit 'special'. Earlier ones (85-90) ran a screw and locknut adjustment setup, one cam lobe per cylinder for the exhaust and the intake. In 1991, they went to a shim setup (though not exactly as per modern bikes) and no-one makes performance cams for 91s, cause they spit the shims out. In 1992, they went to watercooling and completely different cam profiles.

    So I'm stuck finding 1991 cams. CMSNL do them for about 260 euros per cam. That's irritation #1.

    I also need to find pistons. Again, the 1991 is a bit special. Not as special as I can also run 1990 pistons, plus GSX750F pistons, but slightly special. Or I can just admit defeat and get one of three bore kits:
    771 cc (+1mm)
    905 cc (can't remember... +6mm?)
    981 cc (+9mm!)

    900+ needs case boring but will give you as good peak power as an 1100, with the benefit of the 750s 6 speed gearbox. 771 is easier but still not cheap cause I think you need to swap the liners out. I think it becomes about a $2500 motor if I went down the 980ish route, by the time you deal with everything else.

    I could go for an 1100 swap but a) I like being able to service it without dropping the motor so you can pull the cam cover off and b) I'd really like to keep it as a 750. Yeah, I butchered the subframe but other than that it's an original 750 and I do like keeping things original, rather than making them something they're not.

    At some point I'll get some designs whipped up and get the subframe fixed up and then I might just drive it on the road. I had toyed with the idea of getting it ready for the PCRA 1 hour but I don't want to do it with a half-happy motor and burning more oil than the RGV does.

    I have a set of FCRs for it (FCR41s, great for the track, crap for the road) I'll probably sell shortly. If I do enjoy it on the road, I think I might actually try my hand EFI'ing it. Either GSX1400 throttle bodies or modified 600 Katana EFI ones should fit apparently. That at least would get rid of the classic GSXR750 flatspot at 5-7krpm...
     
  19. RobotJebus
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    Intrigued by the idea of making it EFI.
     
  20. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    It's been done before. Mainly needs modification of the softmount intake manifolds and lengthening of the central pipe of the throttle bodies.

    I also started looking at what I could do to EFI the postie :D. CBR125R fuel pump and throttle body would make that pretty simple, though biggest drama is a crank or cam pickup for timing (can't pull tach signal for a microsquirt straight off a CDI coil. Can pull tach signal off the dyna ignition module on the gixxer).