Sounds similar to a problem I had on my car. Very frustrating - sometimes the car would run for 1hr+ with no problem. Other times it would misfire almost immediately. Misfire always on steady throttle opening - give it the beans and it would pull fine. Turned out to be a faulty TPS. A work-around was to 'exercise' the throttle by depressing the pedal fully 10 times before starting the car. This temporarily cleans up the potentiometer within the TPS (much like a scratchy volume knob on a transistor radio) and effectively made the problem go away.

There are two types of TPS fitted to our cars. Most have the type with slots which allow the sensor to be adjusted before being bolted into place. Unfortunately, you will probably find that these are no longer available from Morgan dealers (although I haven't checked recently). They are available here:
[Linked Image]
Also, there is a Cycle Pro equivalent that Harley dealers might stock, although it's significantly more expensive than the AliExpress one.
The later (non-adjustable) TPS should be available from Morgan dealers. Once again - not cheap!

Last edited by Bunny; 27/07/23 08:34 AM.
Andy