Ariel Owners Motorcycle Club

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Hope the photo shows. Are these sprocket teeth marks ?

Hi
I think you should focus your investigation onto the clutch sprocket - I would suggest the bolt from the inner chaincase has dropped out and onto the primary chain where it has been carried back to the clutch sprocket and caused the damage to the lower rear of the chain case - the damage to the front of the chain cases looks like secondary damage caused by this event.
Regards Mick

BobWard wrote:My thoughts are still with gearbox moving forward as you mention travel down hill was this using the rear brake causing the back drag, please check for tightness of the drive chain as this may confirm that the box traveled forward. Bob
Edit :- Having just seen previous post you can check the drive sprocket teeth if a stray part rode over the drive sprocket you Will see the thee damage to one or more teeth where the object wedge in between chain and sprocket. Bob

Thanks Bob, I think you're onto something. I have just been down to the garage for a squint.

The rear chain does feel tight, I was under power coming down the hill without braking until the end, there does look to be a screw missing behind the drive chain-wheel and sifting through the bits of metal there looks to be the remains of a screw although there's no sign of the head as yet. All cog teeth look to be in place but I can see some denting to the primary chain.

So it looks like the screw came loose, got caught in the chain which then pulled the rear chain tight as it passed around the chain-wheel which resulted in the cases being smashed.

Hi Dave
If you offer up the parts of the front of the inner case to the bit in situ you'll be able to determine if the force was forwards or backwards, ie which sprocket was involved.

Edited to add: Your first photo suggests the force was rearwards.
Regards Mick

Mick D wrote:Hi Dave
If you offer up the parts of the front of the inner case to the bit in situ you'll be able to determine if the force was forwards or backwards, ie which sprocket was involved.

Edited to add: Your first photo suggests the force was rearwards.
Regards Mick

I think you're right Mick. It seems to have been pulled rearwards.

What are the numbers of the inner and outer chain cases? Maybe I can help.

To help in getting you back on the road, the inner case is common to all 1936-53 singles, except WD models with the tin cases and 1939/40 250cc models. Any 1936-53 outer case (with the exceptions above) will also fit, although if you use a 1939 onward outer you will need a different clutch dome (of which I have plenty). I would aim to get back on the road then get your 1936-38 outer case repaired in due course.

rein.heerkens wrote:What are the numbers of the inner and outer chain cases? Maybe I can help.

I have not taken off the inner case yet as I don't have a thin enough spanner to hold the crankshaft nut.

The outer case has a casting number but it's hard to read. I have attached a photo below...

paul.jameson wrote:To help in getting you back on the road, the inner case is common to all 1936-53 singles, except WD models with the tin cases and 1939/40 250cc models. Any 1936-53 outer case (with the exceptions above) will also fit, although if you use a 1939 onward outer you will need a different clutch dome (of which I have plenty). I would aim to get back on the road then get your 1936-38 outer case repaired in due course.

Thanks Paul. You're absolutely right, the priority is to get it rolling and spitting flames again. I will be on the lookout for some suitable replacements.

These domed outers as spares dried up years ago. I wonder whether they would be a suitable candidate for re-manufacture?

As much as I dislike modern mods on old bikes,I think a belt primary drive on an Ariel might be an exception............still ,a primary chain bustup takes my mind off the millenial drivers playing with phones while I'm out riding.