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1973 Suzuki GT250 'Robyn': cafe racing commuter

Discussion in 'My Bike' started by supamodel, Nov 29, 2010.

  1. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    $400, trip to southside, made room in the garage for one more bike


    DSC_1758.jpg

    As the bike rolled off the trailer



    DSC_1759.jpg

    The most significant damage to the bike is a missing right-hand footpeg and a bent indicator mount. Not too hard to fix up properly! Other stuff that needs doing is replacing the throttle cable (snapped; GTs use a snazzy 1 into 3 throttle cable to control 2 carbs & the oil injection pump)




    DSC_1761.jpg

    Tank has un-original rattle-can paintjob. Original colour is red. Some rust but it's not as significant as it looks in the pics, the tank is pretty good inside


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    Front brakes need some attention. No brake fluid, master cylinder siezed in the on position



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    Original tail-light, in good condition




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    Oil tank missing the GT250 badge, and shows the original red colour



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    Bit of oil hanging around here, but it degreased off nicely (see later pictures). Oil pump cover came with the bike, just not installed



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    Oil on left-hand side of the bike


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    Speedo lens is a bit frosted but not too bad



    DSC_1771.jpg

    Fork seals are leaking pretty badly. Not a very difficult job to do on these bikes though. Fork gaitors are in brilliant condition
     
    Last edited: Oct 1, 2014
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  2. Madmonk
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    Madmonk Member Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Grats on having room for more bikes. From the photos it looks like its going to be a nice project :)
     
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  3. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Part 2...

    DSC_1772.jpg

    All the fork oil has preserved the front wheel nicely



    DSC_1777.jpg

    After a few litres of degreaser and removing the seat and fuel tank. Absolutely no wash or anything used here, just degreaser and some brushes. It's come up pretty nicely - polish the chrome and it'll look a million bucks



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    Left-hand side of the bike, after degreasing



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    Right-hand side after degreasing. Much, much cleaner. Looks like the oil has come from a weeping join in the 2-stroke oil pipe




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    Forks after cleaning. Just wanted to see how the forks were under the grease; it definitely needs these rebuilt so they don't leak anymore



    DSC_1783.jpg

    Fuel tank is good inside but needs a good paint on the outisde. Seat base has some rust but nothing that's gone through: wire-wheel, sand and kill-rust primer should help here. The seat foam is trashed, will need it being done



    DSC_1784.jpg

    Rear guard cleaned up pretty nicely too, though it still needs a polish. Rear rack is a bit rusty but no cafe racers have rear racks




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    Supa unsticking the brake line into the front caliper




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    10mm brake spanner to undo the brake line, modelled by Supa



    DSC_1788.jpg

    Undoing caliper bolts
     
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  4. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Part 3

    DSC_1790.jpg
    This is why the fuel tap leaked so much: the gaskets are ruined. Should be rebuildable though!

    Things to do:
    * Buy a battery, check all wiring
    * Check coils resistance
    * Check ignition points
    * Replace spark plugs
    * Clean carburettors and air filter
    * Replace throttle, rear brake and clutch cables
    * Adjust oil pump
    * Rebuild front brake system
    * Replace tyres
    * Replace chain (and perhaps sprockets, though they are in good condition)
    * Service fuel tap
    * Cafe-race the beast! - Plans are already in motion for this bit. I've already decided on the paint!
     
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  5. MickLC
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    MickLC Member

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Ring-a-ding-ding! :cool:
     
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  6. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    ... I've already looked into getting some chambers for it. But for now the beast needs to be registered.

    Also, for all those reading along who don't know, I used to own a GT250 so this is an excellent project for both of us. This one is original so it hasn't been played with much, and having rebuilt my old GT a few times, this means I can provide advice to MIZ whenever she comes running in from the garage going "where the hell does this bit go" or "how the hell do I adjust this f*(&*)&n oil injection setup".

    I'm excited about it, and was super-stoked to pick it up on saturday.
     
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  7. Sprinter
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Well only the best people get to own a GT250. Should be a fun job:)
     
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  8. metaltriumph
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Cool! Go cafe racers!

    You can buy my cafe handlebars off my z650 if you were after that style. I need to fund clip-ons (expensive)
     
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  9. Gosling1
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    Gosling1 Forum Whore of Death Veteran Member Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    was this bike the GT2fiddy that Stu from CMC had ??

    :cool:
     
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  10. RobotJebus
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Sounds like an awesome project, can't wait to see it progress.
     
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  11. Stout
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Love that Ram Air System scoop !

    I almost bought a (fairly new) X7 at one stage, which was the final incarnation of these things. It was around the same time as I almost bought an RD400, RG250, etc, etc...I got over it at the time, but a the hankering to own a ringding roadie has been building up again since I bought my trials bike last year.

    Look forward to seeing this up and about.
     
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  12. Moto_Garage
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    :confused:nice
     
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  13. Lurch
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    Lurch Capt. Sense of Direction Administrator

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Brett knows what coming... another old freaking Suzuki!
     
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  14. Michael
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Excellent... :thumbsup:
     
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  15. bushpig666
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Looks to be in better cond than I was expecting. Will be watching progress. I scored my battery from Hal for $90. Great battery. Survived winter even after leaving the heated grips on overnight more than once and comes with a 2 year warranty :)
     
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  16. speedygp
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Fantastic! looks like you got a real original one that someone previously has put some time into judging by the seat base paint job.
    You could keep it "period" pretty original, but with flat bars and chambers Great buy, keep us informed!
     
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  17. supamodel
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    supamodel Secret Aaaaaagent Man Staff Member Moderator Supporter

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Compression testing the GT250

    tl;dr version: GT250 compression tests at 91-92psi on each cylinder; either it's awesome or has a knackered crack seal. supa craps on about compression testing methods.

    My role with this bike is to do what MIZ desires (and teach her some mechanical stuff). First role: GET IT RUNNING.

    I like to do things carefully. This bike hasn't been running for a long time, and I wanted to make sure it had good compression. It feels like it has good compression when I kick it over, but its hard to know. Time to measure it.

    You start by removing the spark plugs. If you don't know where they are or how to remove them, you probably aren't ready to test the compression.

    [​IMG]

    For the GT250, the spark plugs are hard to get at because of the frame spars. 99c plug spanner works nicely here. These are great plug spanners to keep under your seat with a spare plug, especially if you have a 70s 2 stroke prone to fouling plugs.

    [​IMG]

    You also need a compression gauge with an appropriate thread for your spark plug. Car spark plugs are often 14mm (or 12mm on smaller plugs); often bikes run 10mm threads (especially modern sportsbikes). This beast runs 14mm plugs. For completeness, I have shown my adapter as well as the 14mm to 14mm extender for my compression gauge. The extender makes it easier to access deeper heads. On the GT250, I was too lazy to remove the ram-air cooling setup so I left it in place and used the extender. As shown here, remove all spark plugs - this is a 2 cylinder, so you'd hope I had 2 plugs on the ground.

    [​IMG]

    Screw the compression gauge in all the way, you don't want it not sealing against the head.

    [​IMG]

    This is a kick-start only bike, so this part is actually kinda easy. Ignition switch off, kill switch off. If your bike is electric start, work out how to disable your ignition system so you don't burn out CDI systems etc but can still use the starter motor.

    [​IMG]

    Open the throttle all the way. On most bikes, this just means make sure you have access to the throttle grip while starting it. On some bikes, with vacuum-assisted slides, you need to hold the appropriate one open. On this particular GT250, the throttle cable is broken, so it takes a bit of talent to hold it fully open and kick the lovely left-foot kick start (who the fuck decided left-foot kick start was smart?).

    [​IMG]

    Kick the bike over till the compression gauge stabilises. This could be about 10 revolutions or so... about 4 good kicks. Note the reading.

    [​IMG]

    91-92psi for this one (left-hand cylinder). At the bottom of the gauge, in the silver bit, you can see the button to release the pressure and thus make the gauge read 0 again.

    Unscrew the gauge, screw it into the other cylinder(s), hold the throttle open, kick it over a few turns, and note the reading.

    [​IMG]
    Maybe 1 psi less than the other? Still about 91ish though.

    That wasn't set up - that's how it read. Cylinders pretty close to each other. You're usually after cylinders within a certain range (say 100-130 through to 200 psi for a petrol four-stroke motor, 70-130 to maybe 150 psi for a petrol two-stroke motor), as well as not too much deviation from each other (say 10-15% max difference between highest and lowest). Crap compression in one piston could be due to a head-gasket leak, buggered piston, fucked valves (4 stroke), or rooted piston rings. Or other symptoms I've forgotten.

    So the verdict for the GT seems good? They're not bad numbers and close for each cylinder, that's good, right? Yeah, probably. I'm still suspicious, the numbers are so close to each other that I'm worried. See, in the GT series, the central seal in the crankcase can leak, so the pistons effectively share their bottom ends (not good in a parallel-twin 2 stroke). So maybe they're seeing each other's compression and I'm seeing an average?

    At least it's not zero compression, so if I get spark and air:fuel in a roughly right ratio, it should fire!
     
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  18. Sprinter
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    You are so fake..:p
     
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  19. Charlie
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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    I don't think you'd get a transfer of pressure from one cylinder to the other, unless both cylinders fire simultaneously and the cylinder seperating piece of the head gasket was rooted. Once the piston comes up and covers the exhaust and inlet ports of the cylinder, what is happening below the piston should have little affect on the compression results? Obviously as the piston comes down it compresses the air in the crankcase and when the piston nears the bottom of it's stroke this air/fuel is released up into the cylinder, so if your crankcase seals were shagged it would affect your compression figures, but I don't think it would cause equalisation of compression figures?
     
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  20. Charlie
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    Charlie Member

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    Re: 1976 Suzuki GT250 - The Cafe Racer - Miz Style

    Great project by the way! Love reading your write ups too.
     
    #20