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TRIALS GEARING with standard 16T gearbox sprocket.
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Martin hg
somerset
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December 23, 2019 - 3:39 pm
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Hi. I am converting my old D14/4 for the Arbuthnot trial and for some gentle green lane-ing. I have ordered a 58T rear sprocket from Fekked as this was the standard Bushman size (coupled with the standard 16T gearbox sprocket). Has anyone tried this? (Im sure many people have) is it a reasonable way to go when converting a standard D14 for a bit of off road fun? Any thoughts much appreciated. Thanks. Martin.

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Stoo63
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December 23, 2019 - 8:09 pm
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Hi Martin and welcome to the Forum, as you say, this has probably been done many times before, so there should be lots of posts on the site about it already to help you.

You will find just about everything you could ever want on the Forum via the FAQs and technical sections. Just about everything has been covered before- at least twice! It makes life a bit easier when searching to use Google and the template "your query site:Bsabantamclub.com " e.g. "fuel mix site:Bsabantamclub.com” you'll get more focused results than using the Forums internal search engine.  If you can't find it in the mountain of info just ask. The members will be only too happy to give advice. Well done for including your location in your profile, as often their will be members local to you who would love to help and see your bike. If you join the Club this opens extra technical info on the forum in the members only area and gets you discount with a multitude of suppliers and businesses. We all love to see photos - there's a 1mb limit in image size - Help here ** Please log in to view **.....ad-photos/ it may seem a but fiddly to begin wit but you soon get the hang of it.....   

looking forward to seeing/hearing about your progress

All the best,

Stewart

'52 D1 direct lighting plunger; '58 Square Four (project); '55 D3 Battery; '59 D1 direct lighting plunger;  '59 Tiger Cub; '60 5TA;  '76 FS1-E '97 Honda Sky SGX50.

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mcafee
Malton North Yorkshire
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December 24, 2019 - 5:49 am
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Morning Martin,I have a B175 which I use for greenlaning and have competed in the Beamish Trial with it several times.Originally I used the standard gearbox sprocket with a 58 on the back wheel and found the gearing ok for road work but too high off road.The bike has an18 back wheel running a 4inch tyre with a 14 to 58 gearing and I find this adequate for road work and low enough for the steeper sections offroad.The sprockets are 420 size which I got from Trialsbits.All the best with your conversion.   David

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Martin hg
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December 29, 2019 - 5:30 pm
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Hi David, thank you very much for this reply. Extremely useful. May I ask, did the 14t gearbox sprocket need any modifications to the cases? Once again thank you for responding and seasons greetings! Martin. 

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Sponge
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December 30, 2019 - 4:28 pm
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Hi Mate, just butting in here ref sprockets but thought I could add some value to the thread.   I am running a D7 trail bike with 17/58 gearing and it is,  as stated , fine on the road but on the rough it struggles.  My intent is to drop it to 15/58 and see how it goes. 

If you want to run any bigger than 58 on the rear you will need to think about adding a chain tensioner somewhere near the  swinging arm pivot.  The Trail Bronc tensioner is simple, quite neat and uses a A65 part as its wearing component.   

A while back I built a very special D14/4 engine trials bike with 14/66 and it was just right in all ways for my style of riding (slow and wobbly).  I think that 14T is about the smallest you can fit to the 4 speed engine without risking your chain fouling the cases. Any smaller and I think you might be into the realms of specialised engineering work   

With the 3 speed engine a 15T is the smallest you can safely fit with a standard oil seal holder under the sprocket.  My factory standard Trail Bronc runs 14/80 but it has a special factory modified oil seal holder ( BSA part no 90-0450 ) to accommodate the correct chain clearance.  

If you can get one of those oil seal holders then you can safely go down to 14T    

I live in a place where there are lots of hills (everywhere seems to be uphill) so I am converting both my Bantams to 15/47 to make life a bit easier. 

The difference between 16T and 15T is quite tangible.  

Hope this helps mate

Sponge

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Martin hg
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January 1, 2020 - 5:02 pm
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Sponge said
Hi Mate, just butting in here ref sprockets but thought I could add some value to the thread.   I am running a D7 trail bike with 17/58 gearing and it is,  as stated , fine on the road but on the rough it struggles.  My intent is to drop it to 15/58 and see how it goes. 

If you want to run any bigger than 58 on the rear you will need to think about adding a chain tensioner somewhere near the  swinging arm pivot.  The Trail Bronc tensioner is simple, quite neat and uses a A65 part as its wearing component.   

A while back I built a very special D14/4 engine trials bike with 14/66 and it was just right in all ways for my style of riding (slow and wobbly).  I think that 14T is about the smallest you can fit to the 4 speed engine without risking your chain fouling the cases. Any smaller and I think you might be into the realms of specialised engineering work   

With the 3 speed engine a 15T is the smallest you can safely fit with a standard oil seal holder under the sprocket.  My factory standard Trail Bronc runs 14/80 but it has a special factory modified oil seal holder ( BSA part no 90-0450 ) to accommodate the correct chain clearance.  

If you can get one of those oil seal holders then you can safely go down to 14T    

I live in a place where there are lots of hills (everywhere seems to be uphill) so I am converting both my Bantams to 15/47 to make life a bit easier. 

The difference between 16T and 15T is quite tangible.  

Hope this helps mate

Sponge  

Hi Sponge, this is very interesting, I think - after this correspondence - Im going to go 15T with the 58 now (the easy route) and see how it goes. Very best wishes, Martin.

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mcafee
Malton North Yorkshire
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January 3, 2020 - 9:27 am
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Morninh Martin and happy new year,sorry not tohave replied I have been offline for some time.A 14 sprocket will fit without any modification.

David

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bantammad
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January 5, 2020 - 9:15 am
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Hi bantammad ere just wondering what size sprocket do you have on the primary drive ? Regards LES

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