Ariel Owners Motorcycle Club

Hi All,

Have a 48 Ariel 500 Twin Field Master I am attempting to get a "semi" oil tight primary on and have some queries.

Crank Seal: The old Crank Oil Seal was rock hard and have sourced replacement parts from Draganfly. My question is this seal doesn't appear to be retained to the inner primary at all? I can see the old seal has been spinning with the crank marring the inner primary and I don't see any way that it was previously retained? What am I missing here?

Gearbox Seal This old seal "I assume not factory" was "Fit" to the inner primary however the inner primary has a taper, what should be here?

Links to Images here:

Crank Seal 1
Crank Seal 2
Crank Seal 3
Crank Seal 4
Crank Seal 5
Gearbox Seal 1
Gearbox Seal 2
Gearbox Seal 3

Cheers

The crankshaft seal isn't retained to the case. It relies on a degree of compression between
the sprocket and the case to hold the oil in the crankcase.

In my experience with my Square Four it works quite well.

With regard to the sealing the gearbox shaft, the oil should be retained by the cast-in
flange on the chaincase. Again, my experience is that this works well iunless the
flange has been damaged. There is a similar but larger flange on the outer case
keeping oil out of the clutch.

Hello Lee and welcome to the Forum. I think your problem is down to having a primary chaincase inner from a single rather than a twin. To confirm this, can you post a photo of the top of the chaincase inner where it meets the engine please? There should be quite a kick in the line of the top of a twin chaincase inner which is absent on the singles type.
Goodness knows what the gearbox seal was about but something like that was never fitted to Ariels

Thanks guy's, looks like its correct then and someone has just done their best with that gearbox seal....

Photos below of inner, looks like it mite be correct

https://drive.google.com/file/d/1WJV764 ... share_link
https://drive.google.com/file/d/1WS3Rmp ... share_link
https://drive.google.com/file/d/1WTf1Uf ... share_link

will_curry wrote: ↑Thu Nov 24, 2022 3:22 pm The crankshaft seal isn't retained to the case. It relies on a degree of compression between
the sprocket and the case to hold the oil in the crankcase.

In my experience with my Square Four it works quite well.

With regard to the sealing the gearbox shaft, the oil should be retained by the cast-in
flange on the chaincase. Again, my experience is that this works well iunless the
flange has been damaged. There is a similar but larger flange on the outer case
keeping oil out of the clutch.

As I can see evidence of the previous seal spinning against the inner primary, would it hurt to put a little RTV between seal and case on this one? or is that a no no

Cheers

There's nothing in the design to suggest to me that the seal should be fixed to anything.

The Square Four has a pen steel washer between the seal and the crank case and both
were well polished the last time I looked.

I'm not a fan of RTV so I wouldn't bother with it.

What I would do is make sure that the small screw inside the primary case at 3 'clock to the
crank can't come out because if it does it will cause some serious damage.

I looked in the parts list for the early twins and I couldn't find the oil seal listed although it
is listed for later models. There was some changes made to the sprocket and shock absorber
over the years and I'm not at all sure what the differences are.

I can't access the photos of the primary inner, not having access to the google thing the links demand. Can you post the photos on the Forum please? You need to click on the attachments tab below when writing the message, then click on add files and follow the instructions.

Primary Inner Photos.

Cheers

Yet again, I have learned something.

You have a KH inner primary case but it is unlike any I have seen before.

My concern over the primary inner was down to the fact that your primary inner has a much smaller hole for the crankshaft than mine. Added to this is a crack in yours going round more or less where the outside of the hole in mine would be. Having looked at the drawing (which shows my primary inner) I was no wiser. But looking at the crankshaft oil seal I see it appeared on the KH in 1949 and that your bike is 1948. So the larger hole in the back of the primary inner must have been introduced in 1949 but the change is missing from the Parts Books.

My next question then, concerns the crack in your chaincase inner. It looks as if it has been caused by the lip on the crankcase which matches the large hole in my chaincase inner. So, have you still got the original 1948 crankcases on your bike or are they from a replacement engine of a later date? If you send me a private message with engine and frame numbers I can tell you whether they match and when they left the factory, etc.

My guess now is that you have later crankcases which are designed to take the crankshaft oil seal coupled with the original 1948 primary inner which is not designed to take the oil seal. Hence the crack and the grooving in the primary inner.

The function of the crankshaft oil seal is to prevent crankcase pressure from causing the engine oil to go into the primary chaincase and overfill it. I have had the problem on my Square Four which addition of the oil seal suitably cured. Presumably, the first KH models had the same problem.

Send me the PM with the numbers and we can go on from there with what would be the best course of action.

Paul

Having seen the numbers and looked them up, the problem is as I suspected in my post immediately above. The bike was in fact only the 65th twin to leave the factory so a very early example. But the engine, or at least the crankcases, has been replaced by one from 1951.