Ariel Owners Motorcycle Club

Hi All
Long shot, but I was hoping someone may have a pump of the same pattern as used on my 4F, from which I'm looking for the plunger length.

My pump has been refurbished and picks up just fine when stroked by hand, but will not lift/pump when run in a mock-up using electric drill to drive the eccentric shaft.

The pump has been resleeved a new plunger made using the original damaged plunger as a pattern. My suspicion is that the original plunger was also made as a replacement (looks like it) and is slightly too long and not drawing past the inlet far enough; the pump lifts fine when I stroke it by hand a little further than the eccentric displacement, hence my thought on plunger length. Non return ball seems to be seated well and holding suction.

Cam

ohv 4F I assume rather than ohc. I have dims for the ohv one

I do own such a pump but it is on loan to a fellow AOMCC member who is having problems with the pump in his engine. I will alert him to your post.

Paul

Roger Gwynn wrote: Sun Oct 25, 2026 2:18 pm ohv 4F I assume rather than ohc. I have dims for the ohv one

Hi Roger
No, 1936 OHC, with plunger unit. I think the earlier OHC's had gear pumps?

Cam

paul.jameson wrote: Sun Oct 25, 2026 2:41 pm I do own such a pump but it is on loan to a fellow AOMCC member who is having problems with the pump in his engine. I will alert him to your post.

Paul

Hi Paul
Thank you! That would be fantastic if your friend could give the plunger dimension (for clarity, it is a 1936 OHC).

It also just came to mind that the pump bore has just been re-sleeved, so it is possible the suction hole entering the pump bore is either too small, or possibly positioned slightly incorrectly.

Regards
Cam

camstevens wrote: Sun Oct 25, 2026 4:18 pm

paul.jameson wrote: Sun Oct 25, 2026 2:41 pm I do own such a pump but it is on loan to a fellow AOMCC member who is having problems with the pump in his engine. I will alert him to your post.

Paul

Hi Paul
Thank you! That would be fantastic if your friend could give the plunger dimension (for clarity, it is a 1936 OHC).

It also just came to mind that the pump bore has just been re-sleeved, so it is possible the suction hole entering the pump bore is either too small, or possibly positioned slightly incorrectly.

Regards
Cam

Apologies...1935 4F OHC

Roger Gwynn wrote: Sun Oct 25, 2026 2:18 pm ohv 4F I assume rather than ohc. I have dims for the ohv one

Apologies...1935 4F OHC

Correct a gear pump was fitted to the 1931-32 SQ4, a single plunger pump to the 1933-36 models then a twin plunger pump 1937-52 and back to a gear pump for 1953-58. Usually 4F means cammy but in the inimitable Ariel style there was another 4F in 1937 and 1939, which was a 600cc ohv. The 'F' indicates the status or trim in car speak and means 'Standard' as opposed to 'G' for de-luxe and 'H' for Hunter. I leave it to you to work out what the '4' means!