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By Foo Gee
#1836141
I've got an old Mobylette (yes, I'm in to powerful 2-wheel transport) and the petrol cock is one of those dreadful push/pull ones which screws in to the tank. I'd like to use one that is a twist and have one that also screws directly in to the tank.

Unfortunately the former has an 8mm male thread and the latter has a 10mm male thread. I don't want to rethread the tank and have failed to find a threaded taper 8mm male to 10mm female. Can anyone point me in the right direction please?
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By tr7v8
FLYER Club Member  FLYER Club Member
#1836150
Have a chat with your local Model Engineering club. This is 10-15 minutes work for someone with a lathe. I would probably use a 10mm bolt, drilled & tapped 8mm. You could probably use hand tools with some care. Only issue maybe if they aren't standard M series coarse threads.
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By VRB_20kt
FLYER Club Member  FLYER Club Member
#1836169
If you can get a 10mm brass bolt, you can possibly make your own by drilling it and putting an 8mm tap down.
By Bill McCarthy
#1836186
The adapter has to be 8mm male taper to screw into the tank which has an extension on it with a 10mm female taper end. This is much more than a 15 minute job on a hobby lathe to turn tapered threads.
Have a look for gauge connection reducers.
Last edited by Bill McCarthy on Sat Mar 27, 2021 7:56 am, edited 1 time in total.
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By skydriller
FLYER Club Member  FLYER Club Member
#1836190
@Foo Gee have you googled this in french? Im struggling to envisage what you need based on the stuff I see come up - can you post a photo or post details of your all powerful 2-wheeled demon? Im in France if it helps.

Regards, SD.
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By Morten
FLYER Club Member  FLYER Club Member
#1836225
I think FG will need eg a 12-13mm cylinder, through which you drill a 6-7mm hole. On one end you then create an external (male) 8mm thread and on the other end you extend the central hole to fit an internal (female) 10mm thread.

Maybe not 15 minutes but not that much more for someone with the right tools?
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By Morten
FLYER Club Member  FLYER Club Member
#1836249
Something like this? (apologies to real draftsmen out there - haven't done anything like this for 30years or so...)

By Bill McCarthy
#1836284
Find a brass fitting with the 8mm male tapered thread. Find another with a 10mm female thread, cut each bit you need off, get someone to silver solder them together. It’s a right pigs ear cutting tapered threads and it will cost you! I wouldn’t even attempt it on a lathe - you need special attachments.

Purists on the other hand would throw their hands up in horror at putting a modern gizmo on a “vintage” bike. You would be knocking value off it. What’s wrong with the current valve - can you get it refurbed at a motorbike shop.
By Foo Gee
#1836474
Morten's got the idea. This is the closest I can find but not in the sizes I need.

https://bit.ly/3cviSDz

However, I am going to try one last time with one of the actual taps that they come with even tough I have little faith it will last.

As far as purists go, I'm not intending to sell the thing having done a back to metal respray and engine refurb. That sounds really complex but it's about as simple a machine as you can get. The front brake is one of those rubber clamps jobs you get on a push bike!
By Paultheparaglider
#1836478
Any chance of a few photos of the bike @Foo Gee ?

My first ever ride on a motorised two wheeler was on a Mobylette in France. I was bitten by the bug completely.
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By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1836672
Found it. PD-608, the first part. Has an M8 male thread and an M10 female in the first part of the connector. However you might have to buy 30 or 40 of them.

https://www.aliexpress.com/item/973850475.html

https://www.aliexpress.com/item/973850408.html

Unless you know anyone in the US.

https://www.ebay.co.uk/itm/Straight-Adapter-PD-608-4-for-6/174508379376

https://www.ebay.com/itm/M10-1-0xM8-1-0-Female-x-Male-Brass-Thread-Reducer-Straight-Connectors-Fitting-6-/201717981790

That's assuming the threads are M8 and M10.
By Foo Gee
#1839707
I found a decent replacement tap and so far it seems not to leak.

@paultheparaglider - I haven't got an account to host any photos I'm afraid but we have two. My wife has the joy of the Mobylette Cady and I run the much more powerful 92N. I think top speeds are something like 22mph and 35mph respectively. Buzzing along a country lane together is just about as much fun as motored transport gets!