Ariel Owners Motorcycle Club

Hello Albert,
I think the housing you have is possibly correct for the year of your Ariel.
That because it's rather 'square' along the curved top line .
Later ones were more rounded off there.
Did 1934 sidevalves have a oil gauge? if not yours could be from a sidevalve ?

If you want to go drilling it :
See this to get a idea of how the oil lines run :
I think this is a earlier one with a short piece of copper tubing (cast?) in it.


Later ones just had a drilling.
I think this copper tubing was done because it runs very close (over) the main oil inlet channel.

This is a later drilled one but without the holes for the regulator:



I have one with all the holes you need but it is in a very bad state, see pics :
You can have it for the cost of sending (from the Netherlands) and it might serve you as a sample of how to drill yours.

Roger Gwynn wrote: Sat Oct 31, 2026 10:36 am As Paul says there should be a tapping as shown on his bike. From 1938 the opg is fed from the top of the rocker feed pipe that is in turn fed from what started out as the opg feed hole that you are missing. I don't know what casing you have there, more photos please. I have documented 15 varieties so far, not counting Colts!

15 varieties??? I can see you have a lot of fun haha.

I guess the previous owner just had the oil gauge on and never worked... or maybe the original case got damaged with some rock, and as i read these gauges can be prompt to leaking, maybe it got replaced later with a case without the hole??
It looks to me this area has some weld on... hm
Also the casing has some numbers inside, do they orient you? I read something like "MCL" and some stamped numbers, "2629"

Vincent.vanGinneke wrote: Sat Oct 31, 2026 3:40 pm Hello Albert,
I think the housing you have is possibly correct for the year of your Ariel.
That because it's rather 'square' along the curved top line .
Later ones were more rounded off there.
Did 1934 sidevalves have a oil gauge? if not yours could be from a sidevalve ?

If you want to go drilling it :
See this to get a idea of how the oil lines run :
I think this is a earlier one with a short piece of copper tubing (cast?) in it.

The attachment timing housing (3).jpg is no longer available

Later ones just had a drilling.
I think this copper tubing was done because it runs very close (over) the main oil inlet channel.

This is a later drilled one but without the holes for the regulator:

I have one with all the holes you need but it is in a very bad state, see pics :
You can have it for the cost of sending (from the Netherlands) and it might serve you as a sample of how to drill yours.

Hi Vincent, thanks for passing by my post again

Thats super helpful yeah! I think i do want to go ahead and make the oil gauge functional.

I will need help with the kind of thread to tap, as I almost got crazy with my Austin A35 with BSW, BSF, BSP (by they way BSPP or BSPT).... and this irrational inch system!!!
I have an "eureka" gauge but doesnt look very old, so probably the previous owner bought it relatively recently.

I believe that the number 2629 stamped in it should correspond with the crankcase halves numbers on the underside of the crankcase.
I used to have a Ariel that had these numbers matching.
If they dont match it is ofcourse not a problem as Ariel made this engine basically for decades!

Following up with the gearbox, onto the next mystery.
A club member sent me a seal mod kit, and it seems that it fits just fine However, the oil seal still doesnt seem to be the right diameter for my sprocket spacer

The seal is a CHO 00372, 1.750" x 2.250" x 0.250". (44,45 x 57,15 x 6,35 mm in understandable language) but the spacer I got has an external diameter of 43.5 mm, (1.71" in intelligible language) so roughly there's a 1mm gap!

Were they several versions of sprocket spaces too?

What am i missing out here?

Vincent.vanGinneke wrote: Sat Oct 31, 2026 11:57 pm I believe that the number 2629 stamped in it should correspond with the crankcase halves numbers on the underside of the crankcase.
I used to have a Ariel that had these numbers matching.
If they dont match it is ofcourse not a problem as Ariel made this engine basically for decades!

I'll check that, but i guess they are stamped on the inside?

underside

The sprocket spacers vary in length by model and by diameter by gearbox. The C and GB ones use the same spacer OD and seal, the BA a different size. C/GB seal is 38.1mm ID, 50.8mm OD, sorry for the strange units. BA is larger but I don't have the sizes to hand https://draganfly.co.uk/shop/63524/spro ... 2/#3635-96

The spacer OD on my BA (which conveniently is sitting on my bench in bits) is 44.73mm at the least worn section. That would seem to be correct for the seal ID that you have of 44.45mm.