Triumph T140D Bonneville 750.

Tony Jessop, 5th August 2021.

My first proper bike after passing my Test was a Triumph T140D Bonneville 750 “Special”, which I bought new on 1st August 1979. I sold in it late 1980 and bought a Ducati 900SD Darmah Sport and Ducatis have been my main interest ever since.

Over the years I came to regret selling my Bonnie and eventually the opportunity arose to buy another. The one I found was manufactured in February 1979 and originally exported to USA. I purchased it on Ebay from Vagn Jensen Motorcycles, Horsens, Denmark in January 2020 and registered it in the UK in Aug 2020 on an age-related “T” registration.

• The bike was supplied with an indicated mileage of 17,500 miles and had fresh fuel and oils, new battery and spark plugs and engine run prior to the sale.

• The bike was fairly original except for an American made rear grab rail / back rest / cissy bar and after-market rear shock absorbers. The seat, brake discs, side panels, air filter boxes, silencer, rear light and idiot light assembly were all in a very poor condition.

• New rear sprocket and chain were fitted. All the control cables and the perished rubber parts were replaced along with new front fork gaiters.

• Seat base was refurbished and a new seat cover fitted. Lightened and perforated brake discs, an original new rear grab rail and original new idiot light decal and lights were fitted. Wiring loom was checked and all connectors cleaned or replaced if required.

• The ignition circuit was checked, the pick-up and transducer were producing a signal and sparks were present when the ignition was switched on and off but no sparks when the engine was turned over. It would appear that the original Lucas Rita electronic ignition power circuit was still working, but apparently the capacitors degrade over time and after 40 years they cause the control circuit to fail.

• Various electronic ignition systems are available for the Triumph twins but a cost effective replacement for the actual PCB was fitted in place of the original Lucas Rita unit.

• The original air filter boxes and side panels were replaced with after-market items. The Amal MkII carbs were stripped, cleaned and rebuilt using major repair kits. New fuel lines and remote chokes were fitted.

• Despite numerous attempts to kick start the bike it just could it not be coaxed into life; further investigation was required so the bike was put on one side.

• Later, on revisiting the bike and checking the battery, ignition, spark plug gaps, compression and valve clearances the static ignition timing was found to be incorrect. I can only assume that the previous owner had continually adjusted the timing to try and compensate for the failing Lucas Rita electronic ignition.

• Static timing was reset to the factory setting and after a couple of sprays of “Easy Start” the bike fired up.

• She now starts on the first or second kick with the throttle slightly open. Just need to run her up to full temperature, balance the carb mixture screws and set the tick-over.

  • January 2020

  • August 2021

  • August 2021