Suzuki TR750 PORTING

Well, If you are an Suzuki GT750 / TR750 fan no doubt you will have looked up tuning and porting on the internet. I did!

However, the port maps that I found over the years while trawling the internet bear no resemblance to what I am going to show you. I am not sure if the the porting maps that I found on the internet and in books about the TR750 are for a standard TR750 as it left Suzuki or a Barton 750. The Barton 750 started out as a Standard GT750 motor that was tuned by a company in Wales called, you guessed it, Barton. It involved using a 3mm alloy barrel spacer under the barrels and 3mm machined from the top of the barrels. This was the starting point for the Barton tuned motors, and is quite an easy and effective method of raising the top of edge of the GT ports by 3mm.  The genuine TR didn't use the 3mm spacer as the barrels had different liners fitted so the port openings were already higher up the cylinder wall. Fortunately for me, a good friend of mine owns a genuine set of works Suzuki TR750 ex Barry Sheene barrels and a full genuine TR750 complete motor. I have inspected the porting on the ex Sheene barrels and the barrels from the complete motor. They are very different to each other and are nothing like what I have ever seen before. Firstly let me show you the Sheene barrels.

How do I know they are genuine TR?, well I have taken some photo's of the Sheene barrels first. If you have a GT750 you can see obvious differences to the GT barrels.

Firstly look at the exhaust port flange, nothing like a GT750. Take a look at the casting where the oil recycle take off point is on a GT barrel (under the letter R). There is no hole, they have not been filled, they have never been drilled.

Notice how these barrels have downdraft carb mounts with NO WELDING!

Some people converted the GT barrel to downdraft mounts, but if you convert a GT barrel, you will see a lot of alloy welding around the mount

Now that is something I have never seen before!

I have never seen or heard of anyone putting that hole into the barrel liner. There are actually two, one for each transfer port.

Please feel free to contact me if you know what they are for!

 The exhaust port is a massive 55mm wide. Now I have NEVER read or seen any port maps that show a TR750 to have a port that wide.

31.5mm down from the top of the barrel is also very high!

Inlet port is 53mm wide (In Total) and the bottom edge is 110mm down from the top of the bore.

Transfer port is 36 x 17mm and 48mm down the bore

As soon as I get the chance I will be taking pictures of the other set of barrels and taking measurements. They are totally different to these!

 Thunder Road Bikes.

The Classic Japanese Motorcycle Site.