The story of my not totally original TX750 by Stefan Edmueller

I was already inflicted by the screw-driver virus in my moped days and had always ideas about motorcycles but these could not be realized because of budget reasons. So up to 1984 I had to play with smaller bikes from Jawa up to Zundapp.

But in 1984 I discovered the remains of a Yamaha TX750 with a friend. He had exchanged it. The condition was terrible…..,there was nearly nothing that was not cracked, bent, wrongly treated or painted with spray paint. The handle and seat were also not original.

But nevertheless when I saw this “thing” I remembered the cover of “MOTORRAD” magazine with the test of the Yamaha TX750. So there was already something positive, furthermore as the bike could be “pushed” along and it came with a large box of spare parts, mostly worn of course, but good to discover all the weak points of the engine (pitted camshafts and carriers, worn bearing shells and oil pumps, bluish conrods….)

A few days later I could pick up my new bike and parked it next to my Kawasaki’s, a KH250 for the street and a KX250 Motocross bike.

I knew immediately that this heap of rust was going to become a single-seater sports bike but as the Yamaha TX750 basically is a touring bike I had to start by making a plan, make sketches and start measuring everything.

I supposed that the sports use would only increase the thermal problems so I thought it better to increase the oil volume. I made a large oil tank in the rear of the frame and hoped that by the special shape cooling would be enhanced. This proved to be correct. The rear wheel adds to the cooling and even in high summer the sump temperature is max. about 100 °C when I am driving fast.

And there is no oil cooler! As the original oil tank is removed the shape of the bike is also much sleeker, the frame triangle is nearly open now.

As I do like the seat position on my Kawasaki KH250 I decided to use a similar layout on the Yamaha TX750 with Tomasselli’s, rear set footrests and a half-fairing.

Also the relevant seat height was important. The required parts and stays and brackets were all made.

Now I could start with the 2 in 1 exhaust system. The exhaust pipe collector on the cylinder head was removed as it restricts the airflow to the cylinder head very much. Many people doubt why this part was designed.

The original Yamaha sump extension was replaced by a single part, which is the only part that I did not make myself as I do not have a milling machine. The original is too deep (road clearance) and has too many gaskets (3).

Now I could get on the fibreglass parts and their brackets. Even though many details had to be solved I could already imagine that the lines and optics resembled that what I wanted.

During the overhaul of the engine I looked more to torque and reliability than to top speed. The camshaft got bronze bearings, several parts were smoothened and the compression ratio slightly increased. As I did not like the CV carburettors I made new adaptors for 36 mm Dell’orto carburettors with acceleration pumps and also re-worked the inlet and exhaust ports.

From both thermal as optical reasons the classic nice alloy crankcase was not hidden anymore behind a side-cover but as most other parts ground and polished.

The oil filter was moved into the engine and ignition, clutch wire and the drive-sprocket got new covers.

It is not normal for such a bike but more comfortable (especially without a main stand) but I removed the kick-starter with gears, etc. and kept the electric starter. A slightly smaller battery is used, placed into a small alloy carrier as low as possible in the frame and the rest of the electrics were invisible underneath the fuel tank.

As I made a completely new wiring harness, both in the cowling and the seat a central connector was built-in, so that removal of these parts is very easy.

Speedometer and tachometer are original but are mounted together with an ignition switch and an oil temperature gauge on a fixed dashboard. Several small items still had to be done before the first test rides in May 1985. But first I had to pass the TUV tests (vehicle approving tests in Germany)

Fortunately the tests were done by a real interested tester who even made good test-drive and I received the required stamps in my document so that the motorcycle could be registered.

From this day the motorcycle remained practically unchanged (only a transistor ignition was fitted after a few years). This proves to me that it is better to do a lot of work at once and then have a lot of fun for a long period afterwards. The engine was never tested on a brake but the performance and road holding are still quite impressive. The engine pulls smoothly from 2000 rpm and revs even in 5^th gear with the longest final drive ratio into the red line. Not only on country roads and mountain passes but also on tricky race tracks as in Rijeka (Slovenia) there are always amazed people.

Sorry enough due to lack of time I do not ride the Yamaha TX750 or participate in the activities of the German TX750 Club lately.

But as Helmut Lackner asked me already several times to write a small story about my bike I had to do this finally. For further information you can contact me of course. I really do hope that reading this story will please you and I wish you all a good ride this summer!

Stefan Edmüller

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