1973 Suzuki GT750K, Fuel Injected, GSXR suspension

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Suzukidave
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by Suzukidave »

Or put in a GS750 transmission . http://oldjapanesebikes.com/mraxl_GT_Re ... video.html" onclick="window.open(this.href);return false;
the older i get the faster i was
JoostGT
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by JoostGT »

I would like that, but I dont have access to a lathe or GS transmission so it'll have to be a GT tranny ;)

Any answer on what really changed between the color coded gears? Can I swap in a complete tranny with kickstart gear and don't have to worry?
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tz375
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by tz375 »

I believe that they are color coded for backlash/clearance. The wrong color combo might be too tight or too loose.

Maybe I just been lucky so far but I have not had any trouble yet with mixing and matching gears and cases. Try them and see.
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Suzukidave
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Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by Suzukidave »

My reeded / injected engine http://www.suzukidave.com/index.php?sfp ... llYzIzZGI3" onclick="window.open(this.href);return false;
the older i get the faster i was
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Suzukidave
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Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
Location: Lancaster Pa.

Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by Suzukidave »

http://www.suzukidave.com/index.php?sfp ... NkNmZjZGE3" onclick="window.open(this.href);return false;
the older i get the faster i was
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Suzukidave
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Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by Suzukidave »

http://www.suzukidave.com/index.php?cmd ... Y4Y2M1NDc2" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
Last edited by Suzukidave on Tue Dec 17, 2013 5:16 pm, edited 1 time in total.
the older i get the faster i was
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oldjapanesebikes
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by oldjapanesebikes »

tz375 wrote:I believe that they are color coded for backlash/clearance. The wrong color combo might be too tight or too loose........... Try them and see.
That's all I have done so far. When I swapped over a complete transmission from one case to another I did once find that the trannie was locked up - so some mixing and matching from my spares was required of the kick start, 1st and 2nd gears to get the right clearances. Afterwards I found this was covered in service bulletin GT-3 which I have posted at this link.

http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;

8)
Ian

If at first you don't succeed, just get a bigger hammer !
JoostGT
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by JoostGT »

I just realized that I have 2 complete crankcases with matching gears for each, so, ehh, this is a non issue, I'll just use my spare crankcase with working transmission. Why didn't I think of this earlier...

This means that I'll be fitting most parts from my spare engine, but since it wasn't a matching numbers bike it doesn't matter anyway. It does mean that I'm going from a GT750L engine to a GT750A engine, so better gearing and better port timing :)
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tz375
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by tz375 »

That sounds like a plan. Better to us the L cylinders and raise the exhaust port to the same as the A or taller and keep the L Intake port timing. MAB have too much inlet port timing for a mild street bike and it hurts bottom end power and torque.
JoostGT
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by JoostGT »

Can't do that, the L cylinder already has +1.0mm bore and that's the piston size I ordered for the A cylinder. I'll have to live with it. Also someone already attacked the L cylinder with a grinder but it looks terrible and I highly doubt it did any good.
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by SW550 »

I can see the work and pride that is going into this Project of yours.
I am impressed with all of your solutions to your issues/problems and the way you found to fix them.
I wish you the best with the next phrase of this project and I'm sure you will keep us all informed.
The Pic's you provided were great as it shows the steps you did in the process of your upgrades, well done. :up:
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JoostGT
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by JoostGT »

Slight change of plans, I'm going to rebuild the engine all stock, even stock compression and stupid large headgasket. This will be a safe setup to get the fuel injection properly setup and allows me to do some more research. Also (and this is the mean reason), I'm going to see if I'm able to make my own insert head as part of my current study using the university's CNC 5 axis milling station (!). This will happen somewhere in the spring so plenty of time to fool around with the stock engine. This will also allow me to dyno the stock engine and measure changes made with the custom head.

I actually found a company willing to waterjet me a copper headgasket for 60-80 euros, which is not bad but not what I'm going for at the moment.

As for exhaust, I'm still undecided whether I should go the easy way and buy/mod those J&R pipes or if I should "fix" my stock pipes till I have time and motivation to make my own set. I really like these exhausts, they're tucked up nice, short and fat, just don't like the mufflers or their position.
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tz375
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by tz375 »

Inserting the heads is the way to go, but you must have the right sized gasket to avoid detonation.

In your position I'd say screw the J&R pipes at that price. Winter is long enough to make pipes. That way you get to make your own pipes that look and fit how you want them to. With J&R you will also want to remove the original baffle tube and muffler design and replace it with a stinger and decent muffler.
JoostGT
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by JoostGT »

I had some spare time today and I made a port map. After tracing the ports with a dirty thumb on paper in both cylinders they seemed the same, but my method was way inaccurate. So I did it again, with proper precision calipers came up with this, they're both the same, I'm guessing the L cylinder is modified to stock MAB spec:

Image

Using my cheap exhaust program I got this, which suits me just fine because I measured I can fit a max of 120mm belly between the framerails, sidestand and footpegs. Can you simulate this pipe for me Richard? To see if this program makes any sense at all?

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Suzukidave
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Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
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Re: 1973 Suzuki GT750K, Fuel Injected, GSXR suspension

Post by Suzukidave »

Did you decide which way you are going with your chambers ?
the older i get the faster i was
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