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1977 GT500 - to do list

This is a discussion on 1977 GT500 - to do list within the General forums, part of the Caferacer.net Forums category; Hey - how did I miss this one? Absolutely first on the list - the Suzuki T/GT500 cannot be run on premix!!! Use the oil ...

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  1. #11
    Senior Member Diamondj's Avatar
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    Hey - how did I miss this one?

    Absolutely first on the list - the Suzuki T/GT500 cannot be run on premix!!! Use the oil pump! You will need to drill the crankcase for oil flow if you want to go the premix route. Otherwise you will starve the crankshaft bearings.

    The T500 and GT500 engines are practically the same. The GT has the PEI electronic ignition which required a different crank snout and different milling of the crankcases to fit the unit. Porting is milder than the early T500s but they did that around 1973 to distance the T500 from their new mid-sized triple the GT550. The GT500 also has a disc brake vs a drum on the T models. The tank is a GT750 unit and the seat pan and upholstery were changed to suit. This means the tank mount and seat mounts are different on the GT frame vs the T500 frame. Otherwise the frames and wheelbases are identical.

    The GT500 can be run on the track without a battery as the PEI is a generating unit. You will need to disconnect the bulbs as the battery acts as a damper for them and you will burn out all of them with the battery out while running. The silver PEI controller boxes can burn out but the circuits have been mapped and they are not difficult to build. There's a good trouble shooting guide in the factory manual which you can download from here:

    http://file.walagata.com/w/sundialmo...SuzukiT500.pdf

    You should start with doing a pressure test on the engine to determine the shape of your crank seals. This will tell you if you need to split the engine open or not to have the crank rebuilt. You can build your own test set-up for about $25 or so. Let me know if you need details on this.

    Seals are available. Here in the US three of the four seals are available along with the four o-rings needed. The right side crank seal has to be ordered from the UK. Not sure what your parts situation is like in Israel. Plus you will need someone that knows how to rebuild a two stroke crank.

    Crank bearings and connecting rods have long been NLA from Suzuki. If you need the crank rebuilt and have to replace these items, they are available from Pete O'Dell in the UK:

    TR500 Suzuki Specialist GT500, T500 Suzuki

    Stainless chambers - really slip-on chambers like the old Allspeeds are available from Titan Performance in the UK. These seem to be good for street duty but you would want something that tucks in tighter like Swarbricks if you start racing your GT500:

    www.classic2strokesuzuki.com - About us

    Swarbrick Racing - Specialists in Competition Exhaust Systems - Lancashire - UK

    The Swarbricks are in kit form and I do not know if he could supply you a stainless kit. They are excellent pipes when assembled by someone that knows what they are doing.

    The T500/GT500 has a wide ratio gearbox which is not the best for racing duty. Nova Transmissions in the UK has both close ration gearbox kits as well as straight cut primary gears for the 500. It's all nicely made but expensive:

    Nova Racing Motorcycle Transmissions/Gearboxes - Home

    As for porting specifications, Muzza has his "old reliable" specifications that work well for someone starting out. In fact he has a full race prep section that may be of use to you:

    Home of the Classic Suzuki Two Strokes Compendium T500 GT750 TR500 TR750
    Suzuki 500 race preparation

    And by the way, that's my GT500 race bike in my avatar.

    Jim
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  2. #12
    jcw
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    Senior Member jcw's Avatar
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    Quote Originally Posted by Ravivos View Post
    (have a look below at the picture, this is the 4-2-1 exhaust i am building for my XJ550).
    Attachment 15388
    Those pipes look huge for a 550. Won't you kill your exhaust gas speed and torque?

  3. #13
    Senior Member Ravivos's Avatar
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    Hi Diamond,
    Now that! is solid information! thanks...

    As for the premix, i have read about it and will service and keep the oil pump.

    As for not running battery, i will need to have working lights on the bike in order to make it street legal, otherwise i wont be able to ride it at all... is there a way to build a voltage limiter (high current zener diodes) that will act as a dumper and regulates the voltage?

    i think i need to split the case anyway, since the engine was not started for over 15 years, and i really dont know what is the engine's internal condition. any thoughts on that? should i avoid splitting it and replacing the seals as i go?
    can you further elaborate on the pressure test ?

    thanks for the links, will surly check every one of them for information.
    hopefully, i will be able to conclude the deal on Friday, as there was a small matter of ownership, but that got sorted out.

    do you have any other pics or videos of the bike running? how is is in general? how is it on the track? do you like it?
    thanks again.


    Hi jcw,
    the pipes are on the large side of things, but not too much... running some calculation, i got the ideal primaries at 30mm ID , ended up using 35mm ID, i know it is too big, and if the engine wont run properly with these pipes, i will have to ditch them and build a new set...
    i enjoy the design and build, although very time consuming, i am trying to learn as much as possible as i go.

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  5. #14
    Senior Member Geeto67's Avatar
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    here is everything you need to know to start to build a hot shit T500/GT500:

    Suzuki 500 race preparation

    some of it is a little out of date but you'll figure it our pretty quick.

    Where is Diamondj to weigh in here with his vast suzuki knowledge.
    Ravivos likes this.
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  6. #15
    Senior Member Diamondj's Avatar
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    Quote Originally Posted by Geeto67 View Post
    here is everything you need to know to start to build a hot shit T500/GT500:

    Suzuki 500 race preparation

    some of it is a little out of date but you'll figure it our pretty quick.

    Where is Diamondj to weigh in here with his vast suzuki knowledge.
    I was about three hours ahead of you (scroll up!).

  7. #16
    Senior Member Diamondj's Avatar
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    You could get a small gel cell 12 volt and use that as your voltage damper.

    I had thought you were talking about racing this bike which would preclude a lighting system? Maybe you just meant track days?

    To pressure test the engine, get a small hand pump for basketballs with a pressure gauge on it. Something like this:

    Name:  Mini_hand_air_ball_pump_w_gauge.jpg
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    A set of spark plug non-foulers - these are made to raise a spark plug up out of the cylinder head. You want the shorter ones with a 14mm outer thread from an auto parts store... Like these:


    Name:  eng114_pict00110.jpg
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    A long rubber tire valve stem - also from the auto parts store

    Trim the edges of the valve stem seat with a pair of scissors, stick it into the female end of the non-fouler and seal it with JB Weld or Araldite or something similar. Once it dries, you replace a spark plug with the non-fouler/valve stem thing you made. You'll then need to remove the intake manifold and exhaust pipe on that cylinder and seal off the ports on that cylinder. I use pieces of scrap plexiglass from the local builder's supply with a thin layer of permatex that's the right size to seal the port and bolt holes drilled to match the bolts on the cylinders. Then I refit the intake manifold and the exhaust pipe collar minus the header pipe and run the bolts down until it's air tight. Attach your air pump to the valve stem/non-fouler that is screwed into your spark plug hole.

    Pump up the cylinder to NO MORE THAN SIX LBS of air pressure. The rule of thumb is six PSI for six minutes. If it holds, your crank seals should be okay.

    In regards to splitting the cases - if the crank seals are okay and the kick starter works (the pawls are not worn and in need of replacement) I would leave it alone for now.
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  8. #17
    Banned Witworth's Avatar
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    Send the crank to England and get someone who knows what they are doing, to check it out and rebuild it. Experience in a specific model is very useful.

    XJ: The factories know what the I.D. should be for road bike exhaust headers. Bigger is rarely better. It usually just results in flat spots, surging and loss of torque.

    Danger, is my business."

  9. #18
    Senior Member Mark Burton's Avatar
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    Quote Originally Posted by Witworth View Post
    Send the crank to England and get someone who knows what they are doing, to check it out and rebuild it. Experience in a specific model is very useful.

    XJ: The factories know what the I.D. should be for road bike exhaust headers. Bigger is rarely better. It usually just results in flat spots, surging and loss of torque.
    Danger, is my business."
    Oh, only last week you said this....

    [QUOTE][Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

    I would say the OP may be better guided by Diamondj
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  10. #19
    Banned Witworth's Avatar
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    [QUOTE=Mark Burton;332521]Oh, only last week you said this....

    [Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

    I would say the OP may be better guided by Diamondj

    Getting a TS crank apart and pressing it back together isn't manufacturing. It's basically on the level of skilled tinkering. Like Napoleon said, the British are a nation of tinkerers. Tinker tailor. Hello soldier sailor.

    On a brighter note, if you need any crank parts, they'll most likely have been manufactured in Taiwan. So no need to worry about quality.

    I've done plenty of twin and triple TS crank rebuilds, it's pretty easy if you follow the correct steps. Just trying to do the first one without following the right procedures is just a nightmare.

    Danger, is my business."

  11. #20
    Senior Member o1marc's Avatar
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    [QUOTE=Mark Burton;332521]Oh, only last week you said this....

    [Yep, but the peak of British design and manufacturing prowess was 1955, and it's all been downhill from there. That is irrefutable./QUOTE]

    I would say the OP may be better guided by Diamondj
    What, Whit contradicting himself? Not here.

    He could have his own forum and have discussions all day long. And never be wrong, or right.
    www.CreativeCandy.org

    I carry a gun because I'm too young to die, too old to take an ass whooping, and a cop is too heavy.

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