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1964 Bantam D7 T, Trail Bronc.
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IEthatsME
Riverside Ca./Callander Scotland 50/50
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January 30, 2019 - 1:04 am
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I aquired this project at the weekend, I had never heard of the Trail Bronc till then!SAM_0007.JPGSAM_0044.JPGSAM_0085.JPGSAM_0088.JPG

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IEthatsME
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January 30, 2019 - 1:06 am
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SAM_0095.JPGWhat colour should it be. The ones I see on the internet all seem to be blue. Quite a few layers of paint on here.

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IEthatsME
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January 30, 2019 - 6:09 am
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The specs for this bike say a 375 Monobloc carb which is a 7/8" model. The bike is missing it's carb but I have a Monobloc 376 (15/16") on hand. Will it work? Should I widen the inlet port on the cylinder by 1/16" ?

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sunny
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January 30, 2019 - 10:14 am
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your    not  yet   probles  are   the monoblock has  2  bypass holes  1 in each  part of  it  thay must  be  cleaned  out   ///   no 2  is the high  tention  coil  fited  at BSA  has  a low  output  of  15ooo volts  thats  wy  the  s/p gap  is only about  18 thow  and  not  25   thow  /// no3  you  must NOT solder the HT lead  to  the  HT Coil    try a  coil from  a   mower    ther  beter  nowadays   soutable  for a   25 thow S/P gap     using a power tip plug,    alll  that  will  be a  start  for you  if  it had  a  Bronc   rear  mudgard  the  hole  centers  for  the  stay  is 14 and  1/8  im/ inches 

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Paco2cv
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January 30, 2019 - 10:48 am
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I have a Bronc too which came like this, unused since 1970s. It should be Sapphire Blue but whilst searching out details about the model I came across a article on line which stated that dealers could not sell the things and some "updated" them in house to match the 441 models, so they ended up yellow with the large and simple BSA logo in black. Not sure if that helped shift them though.

bronc-start-copy.jpg

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IEthatsME
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January 30, 2019 - 8:45 pm
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Pac, what is the length  from bolt hole to bolt hole, and diameter of the rear mudguard (fender) stays?

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Paco2cv
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January 31, 2019 - 12:25 pm
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IEthatsME

The overall length is 385mm.

From centre of bolt hole to centre of bolt hole is 360mm.

The tube is half inch / 12.7mm

The flattened ends are 40mm each

If you need anything else just ask.

mudguard-stay.jpg

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IEthatsME
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January 31, 2019 - 8:25 pm
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Pac. That's perfect. Many thanks for the help.

I found under the red paint on the back mudguard, sapphire blue paint.

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Sponge
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February 1, 2019 - 5:01 pm
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Hi Guys,

Both bikes look to be authentic Trail Broncs - the rear fenders are certainly correct but for some reason I have found that US riders liked to cut the fender off short so it is now hard to find a complete original rear TB fender. Both fenders have been shortened.

Trail Broncs were supplied in Sapphire Blue on the West Coat but the color was called 'Nutley Blue' on the East Coast - in fact exactly the same colour.  Bearing in mind the BSA habit of having Monday to Friday colours anyway.  Most TBs had a white prancing horse decal  on the gas tank with a gold BSA and red Letters. The decal was 'handed'  - so on the original factory decals the white horses faced forward.    I have a suspicion that he horses changed sizes on different model years as I have gas thanks with two different sized horses on them.   

I note that on Paco's TB the original exhaust pipe and muffler is in place and that is,  also,  a good thing as the bend for the TB pipe was unique to that model and these correct TB pipes are very hard to source nowadays.  The right side pillion footrest hanger is also slightly different with a welded bracket to position the pillion footrest. The silencer / muffler bolts to the footrest bracket where the pillion footrest usually goes.    

TBs were supplied with a 47 tooth rear sprocket as standard fitment to the machine but the bike came with an additional 80 tooth sprocket and a spare length of rear chain that the owner could bolt onto the bike for use on very steep terrain.  It is my understanding that owners would try to obtain a spare back wheel in order to bolt up the 80 tooth sprocket and thus make it easier to do the swap over.  There are also some slight differences to the rear wheel build up and some unique parts.   

Both front and rear wheels are 19 inch rims with a WM2 on the rear with security bolts.  Original tyre fitment was a Dunlop sports - cleated tyre.

TBs had folding footrests and a very neat little rear chain tensioner which came into play when the 80 tooth sprocket was being used.

Early TBs had D1 type forks - whereas later models had D7 telescopic forks with gaiters.  The fork stanchions were hard chromed. 

Front and rear brake actuator levers were also chromed. 

Dual seat in grey and dark grey with a simple side stand on the silencer/muffler side. 

In order to meet US West Coast noise regulations the muffler was quite restrictive and hence the bike was very quiet when running.  This also explains the different carburettor settings on the TB but also because West Coast riders could easily be riding them to mid to high altitudes which would certainly effect carburettor settings.   

Just the standard air filter with a built in strangler for cold starting but I have seen photographs of Trail Broncs with a larger 'box type' air filter fitted which undoubtedly was an end user modification or supplied by the dealership on initial purchase. 

No side panels or centre furniture was supplied although lighting coils were installed in the WIPAC generator in case the owner wanted to fit and run lights.

I have attached a photograph of two TBs side by side.  The front one is an unrestored West Coast TB with D7 forks and the 80 tooth rear sprocket. The far bike is a restored East Coast TB with D1 forks.  I have also included a photograph of the white horse decal on the East Coast bike. Trail-Broncs.jpgTB2TANKhorse.jpg

Always happy to help if you have any questions during your re-activations. 

Please also be aware that there is a TB SME in the club ( not sure who but its not me) so he may be in a position to provide additional information etc.   

I hope that this helps

Sponge

 

 

   

  

 

     

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IEthatsME
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February 2, 2019 - 3:17 am
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Thanks for the information, it's really helpful. Mine appears to have the later D7 forks, though the gaitors have long gone.  It also has a 60 tooth rear sprocket and  a 14 up front. The back mudguard has been shortened as you mentioned. I found out from the VMCC that it left the factory July 3rd 1964 with the frame and engine number it still has. Interesting that the decals I see for sale don't look like your originals.

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Sponge
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February 2, 2019 - 11:06 am
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Hi IE,

I recall a quite interesting conversation with a quite angry gentleman from Essex who stated that there is nothing rare or special about the Trail Bronc because it was made up from parts taken from lots of different models and hence anybody could make one if they wanted to.  I disagreed because you could say the same about the Rocket Gold Star and there are some very unique parts on the Trail Bronc. It is the sum of the parts from the factory that matters (to me anyway) - it turned out he was a motorcycle breaker and was looking to get my Trail Bronc cheap so that he could break it and sell it on in pieces.   I sent him away with a flea in his ear.   After all - anybody can make a Rocket Gold Star by using parts from a number of different BSA bins - but an original RGS is an original RGS.   The Trail Bronc is an important transitional machine in the BSA Bantam story but the mid 1960s US Market was probably looking for something a bit more powerful and with a 4 stroke propulsion unit - such as the B44.   I think that the BSA directors and marketeers hadn't really got a full understanding about just how remote the US wilderness is - Americans like to get deep into the wilderness at weekends on hunting trips etc and it has to be reliable - messing around with 2T oil was also a pain.  A US trail bike, therefore needs to be very reliable and uncomplicated, a Bantam can be that but you need to understand two strokes and their quirks to keep the things dependable.  My 1966 Trail Bronc was abandoned under a tree, then thrown into a shed in the Washington State forest for many years because it would not start, the owner had to hike out of the forest.   I replaced the condenser - added new fuel and did some cleaning out and it ran - after 36 years !!!             

14 tooth front (gearbox sprocket) was standard fitment on the Trails models but it needed a special oil seal retainer behind it to allow for reduced chain clearance. Another little difference that I forgot about.   Rear sprockets were readily available in different sizes, especially if there was a Triumph dealer around who could supply Tiger Cub sprockets - the most likely sizes would be 47, 58 and 80 but I have seen 52, 60 and 66 as well.   

The special chain tensioner is an extended brake pedal pivot with an A65 primary chain tensioner.  I have seen Bantam Trials riding owners struggle to find a chain tensioner solution for a Bantam while the simple solution was always there from the factory.   

The fork gaiters are simply D1 gaiters with a retaining screw clip for the top and the bottom. They are easy to source - I got mine from C&D autos. The original clips are now very difficult to obtain but I guess not impossible.  Bantam John may have a box of them somewhere.

The decals are available from Bob and Marcia Derrick who advertise in the Banter and online.  Bob can sort you out with a set of 'handed' decals in vinyl or waterslide.  As mentioned the decals came in lots of different shapes and sizes but all had the Horse and the BSA Logo.   Also note the 'Made in England' script across the headstock - original fitment from the factory.   

Onwards and upwards.

Sponge    

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JulianS
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February 2, 2019 - 12:18 pm
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From the 1965 West Coast US brochure.

 

The US East Coast distributor was BSA Incorporated, Nutley, New Jersey USA hence the "Nutley Blue" colour.1965-US-Western-edition8.jpg

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IEthatsME
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February 2, 2019 - 5:58 pm
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Thanks for the info Spnge.  Just for fun I'll measure mine and see if would fit in the back of my car, though I don't have a giant 60's American station wagon.

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Paco2cv
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February 2, 2019 - 6:59 pm
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My Bronc was supplied to Hap Alzina and ended up in Washington State. It came with a file of old papers, receipts etc plus a fascinating letter from BSA in England telling him they could not help with a manual and he should speak to the importer, It also came with the original and unused large rear sprocket although the extra chain links had disappeared over the years. It looks like this at the moment but coming back together quickly now.bronc-at-the-moment.jpg

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Sponge
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February 3, 2019 - 5:00 pm
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Hi Paco2CV, your project is looking good and I see you have the folding footrests and the chain tensioner in place.  Please keep the updates coming - it is going to be good and I would love to see how it turns out.  

Hi IE, my TB does not fit into the back of my Land Rover - but it fits nicely in the back of a Toyota pick-up truck.

Onwards and upwards

Sponge 

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IEthatsME
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February 25, 2019 - 2:48 am
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Found a broken pinion gear when I opened the cases up. Looks like the hardened pin came out the shifter and got in to the gears. The rest of them look perfectly fine. Can the pin be tack welded in place?SAM_0154.JPGSAM_0138.JPG

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sunny
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February 25, 2019 - 9:35 am
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you  need to  see  if  the  pin  is smaller  one   end  if  it  is use that end   with  a    small  groov  in it  8 mm  from  the  end   for  the  spring  to  rest in  this  willl help  the  spring  to  keep  the  rod  in  place    the  spring  has  to be  fited  the  rite  way   around  ,,   tak  weld  if  you  wont   

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IEthatsME
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February 25, 2019 - 5:10 pm
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Thanks Sunny. I'll take a closer look at it once I get the parts cleaned up.

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mike p5xbx
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February 25, 2019 - 5:48 pm
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the selector fixing bracket is also broken
think i would try and get some good S/H parts then try to repair all that

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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sunny
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February 25, 2019 - 7:11 pm
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 the   pin  must   be  a  tit   fit  &  be  as one   with  the  fork    can  you  do  a photo   from  the  top  so i  can  see  the  legs  of  the  spring  please

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