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Project 73 Suzuki GT380

Discussion in 'Other Projects - Other Bikes (non 250's)' started by kiffsta, Sep 7, 2019.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    It's going to be a shame to get it dirty
     
  2. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Boyer Brandson (Small).png
     
  3. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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  4. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    90 CBR250RR ,Suzuki T500, 1973 Suzuki GT380 and a cheap arse XVS1100 whcih I kind a like
    Wired up the electric and everything works as is should , that is a big win for me


    0DD82D65-6DF8-4DEF-BF35-8B9F74DA0EBB.jpeg 2006C670-6013-43A2-8498-A077806250A9.jpeg 6027BB70-68C0-4273-972F-EA7218477CED.jpeg
     
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  5. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Fitted up my electronic ignition , I have spark :)

    Only another 2 weeks till my exhausts arrive

    B026768E-4D03-46D7-8039-1B30B20ECE81.jpeg
     
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  6. risky

    risky risky

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    wonderful.should be good for may 2nd. may win top suzuki!8 weeks to go.
     
  7. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Mate, you're already way ahead of my electrical skills! Good job. Are you planning to take the bike to the National Rally?
     
  8. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    I am hoping to take it to Toowoomba, it is my sons Birthday on the 1st so I might just come for a ride up for the show and shine , not sure yet

    I am just waiting on some new cables from the Netherlands and my pipes from the UK then I should be sweet
     
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  9. Andych

    Andych Well-Known Member Premium Member

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    Your son is in good company with that Birthday Chris :party:
     
  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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  11. Suzukititan

    Suzukititan Active Member

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    Following your GT380 resto with interest . It will be a beauty. Hope you are not neglecting the old T500. Looks as if a few more $$$ spent on the 380 than the Titan. I bought a new 1973 GT550K, replacing my T500J - a disappointment, until replaced in 74 with my first foray into 4 strokes and Ducatis- an860GT. Keep the photos of the 380 coming.
     
  12. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Hey Chris, good to hear from you.

    things have come to a crushing halt , I hooked up the old exhausts and attempted to start the bike. After half an hour of kicking it , I had a few coughs , But it would not start and the plugs were dry. I removed a carburettor and put my hand over the carb boot and kicked it , the amount of suction was quite low ,
    It is as if it can’t suck a charge of fuel through.

    I ran compression tests on each pot and I get 125 psi cold across all 3 which is pretty good compared to a couple of other guys I know who have just built gt380 engines.

    I have made my own 2 Stoke leak down tester and have 6 psi going into the carb inlet , I have sprayed soapy water around the motor and there are no bubbles from the cases so I think I can rule out that the cases have leaks. To be fair , I am a bit lost as the timing is spot on.

    I also removed the electronic ignition and put the points back in to rule out ignition issues. Things are a bit quiet at the shop ,
    I might put it back on the lift and work through and try and work out what’s going on.

    good news is that my pipes have shipped from the UK
     
  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Dumb question - only two wires coming from the ignition plate, so the one single coil fires all three plugs three times per revolution?

    So it cannot be mistimed for the wrong plug/cylinder
     
  14. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    The Boyer kit fires all 3 coils at once , hence the 2 wires , wasted spark system
     
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  15. ShaneP

    ShaneP Well-Known Member

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    The exhaust aren't blocked? Crank seals ok? Though I wouldn't think all 3 at once. The exhaust ports seal by the piston skirt, so if the pistons are dry it may just leak past. With the plugs out there should still a lesser compression stroke as the piston goes down. Give us a call if you get stuck, I'll see if I can help.
     
  16. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    I did check the exhausts and they are not blocked , the crank has been rebuilt with all new seals and bearings

    I have spoken to a few old school
    Mechanics who have lots of 2 stroke experience , there was a suggestion of using a roller starter to see if I can get get the motor spinning faster than the Kickstarter will generate: one of my customers has one and is going to drop it off
     
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  17. gregt

    gregt Well-Known Member Premium Member

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    I haven't followed this long enough so I'll ask. Are you using standard coils or Boyer ones ?

    I struck a similar problem recently on a Honda racebike when changing ignitions. It had used a Boyer which had failed so I made up a similar setup - twin lead coil firing twice every revolution with a magnetic trigger.
    I found it was very sensitive to coil primary resistance. The same setup firing once every revolution worked fine with a 3ohm coil.
    Twice every revolution needed 1.8ohm coil. The Boyer one was around 2.0 ohms.
    The 3 ohm coil would fire when the engine was turned over - plugs out in the air - but under pressure, no way.
     
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  18. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    I know some of the early CB750 conversions (from points to aftermarket ignition) had issues. Only way to prove it would be to go back to standard GT380 ignition system. From a casual observer point of view, it sounds like that engine is mint and should fire up without any issues.
     
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  19. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    what coils would you recommend ? , mine are 45 year old OEM ones, I have been looking and it is mostly cheap Chinese crap available
     
  20. ShaneP

    ShaneP Well-Known Member

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    Dirt bike coils?
     

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