If you have a spare slide with a greater cutaway, try that. Modern fuels seem to be requiring changes from standard carburation and richness of mixture at small throttle openings appears to be one of the problems, to me at least.

The late Mr R Saunders told me that he had scrapped the prf converted frame which came with Peter Ferbrache's 250.

I have a NOS adjuster available if you want one.

In my experience, these threads eventually suffer from rust and seize up. Freeing off from this may well be the cause of your problem. So make sure that the thread is suitably protected with copper grease or similar when you re-assemble.

I have sent you a private message.
Paul

I had a 1957 NH where the previous owner had filled the GB box with grease, just the same as he had done on his earlier Ariels. It worked perfectly well.

With an oil filter in the return line I have gone over 20,000 miles without checking the sludge traps. I know of people who have done much more than that but I don't know their frequency of oil changes, how clean the engine was inside when it was rebuilt, etc.

If the gearbox is for a 56 bike, then the 54 mainshaft will be the wrong length. The different lengths are fully explained in the Drags catalogue and under Gearbox in the Ariel 4-stroke part of their website. Someone will do you a straight swop, I would expect. The GB5 gearbox is the same as the GB6...

Go to your local bicycle shop and get one of theirs to mount on the handlebars. This is the cheapest and most accurate option. The problem you face with a speedo driven from the gearbox is that the PA type used prewar (and in 1946/7) have the drive at right angles to the case ie parallel to the face...

Charlie - I have sent you a private message.

I was working on a Mk I front crank today and, as is my practice, I put the crank into the parts washer and applied the pump hose to the drillings. These I make sure are scrupulously clean by means of a variety of tiny bottle brushes. Starting with the hose pumping cleaning solution in through one s...