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Exhaust port question 175 Bantam
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purglaspete
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April 25, 2019 - 4:31 pm
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hello I have a neighbour who has just bought a bantam 175 D14/4 and he ordered a new  high level exhaust for it , the one that came is too big it has an OD of 1 3/4" , the original one on the bike is 1 3/8" O/D  my question is do the bantam barrels have different exhaust bore sizes depending on what model it is or year that it is .   The bike is a J reg , any help would be greatly appreciated as he is attempting to build a trail/trial bike 

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mikef
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April 25, 2019 - 10:04 pm
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Hi.
     Usually a J reg Bantam would be a B175 not a D14/4. Anyway, a D14 or a B175 should have the larger bore exhaust.
I just wonder what that bike actually is. Best thing to do is let us know the frame and engine number. The frame number should be stamped on the left hand side front engine mount and the engine number will be on the top of the crank case near the front chain guard mounting bolt.
Bantam barrels do have different size exhaust bores. D1 - D10 have the smaller bore and the D14/4 and B175 have the larger bore exhausts.
It could be that this Bantam has a D5, D7 or D10 barrel.
All the best.
               Mike.

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Mags 1
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April 25, 2019 - 10:05 pm
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All Bantam barrels have the same smaller male thread on them, later four speed models used a double threaded extension piece of steel that allowed a bigger collar and downpipe to be fitted.

Four now on the road and at least several in bits.

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mikef
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April 25, 2019 - 10:20 pm
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Hi Dave.
        Very interesting point there. I have seen barrels with that double threaded extension fitted, but I have also seen some that just seem to have a larger exhaust port and no extension. It's a bit hard to see on the barrels that I have looked at as they have had a good coating of rust and carbon. Does anyone else have a definitive answer?
????
         Mike.

     

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mike p5xbx
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April 25, 2019 - 11:17 pm
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you need the large bore Exhaust adaptor
item 3 Exhaust adaptor 82-8296
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D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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Peterg
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April 26, 2019 - 10:03 am
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Definatively all Bantams had the same size thread on the barrel. As said the larger bore exhaust was achieved by the screw on adapter. Go for the notched version if youi can find them. The simple threaded version is difficult to tighten down enough onto the barrel to stop it unscrewing when unscrewing the exhaust pipe collar (which is really annoying!).

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purglaspete
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April 30, 2019 - 8:22 pm
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I would like to thank everyone for their help on this when I see my neighbour tomorrow I shall show him all of your replies , and see what way he wants to go with his bantam , I will let you know how he goes on with it regards pete

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purglaspete
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May 2, 2019 - 8:22 pm
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Hello I had a word with me neighbour and he got me some numbers off his bantambike on the engine it has PC12698 D14B  and on the frame there was some number but he couldnt make out the first 3 numbers the rest are  ???1309B175 .regards pete

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wildun
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May 2, 2019 - 11:49 pm
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Those numbers confirm that it is a B175 frame fitted with a D14 engine, or at least crankcases. In which case, the engine cylinder barrel should have the exhaust adaptor ring fitted, as in post 5, to take the larger bore pipe which has been correctly supplied to the owner. So I suggest that he purchases one of these.

The next query that he will come across is, does his silencer fit the larger bore front pipe or has he not got that far yet.

1951 Bantam D1 125, 1954 Bantam Enduro, 1970 Bantam B175, all Bantams on the road and ridden regularly, 1995 Yamaha Diversion 900 and 2016 Honda Integra 750 scooter. Horses for courses, all very different to each other, but a bike for every occasion.

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purglaspete
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May 10, 2019 - 9:00 pm
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hello again I have seen my neighbour and the barrel has just the small port fitting it does not have the round bit that screws on to take the bigger exhaust pipe , he was also asking me is there anywhere up here in the northwest of england that does rebores and pistons for this engine , the piston that is on the engine looks ok but the barrel is scored it looks like the clip from the gudgeon pin has come loose at some time , is this a common problem on the bantams or is it just bad luck on his part, also he said something about suzuki pistons for the bantam , and how big can the barrel be bored out to remove the gouges in it . as usual any help would be gratefully appreciated when I pass it onto george

regards pete

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cocorico
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May 10, 2019 - 9:11 pm
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That sort of stuff can already be found on the forum. Try typing the following into your browser: rebores site:bsabantamclub.com/forum, you can change the 'rebores' for other queries, such as 'piston circlips', 'suzuki piston', 'exhaust adaptor', etc.

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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Peterg
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May 10, 2019 - 10:44 pm
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When Bantams seize it is usually around the area of the gudgeon pin or just in front where the rings are pegged. Before deciding on a rebore he needs to take it to an expert who can judge how much the cylinder needs to be bored to take out the scoring. Check out Rex Caunt's site. His 185cc piston kit is the largest they can be taken out to.

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Mick W
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May 13, 2019 - 11:39 am
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he was also asking me is there anywhere up here in the northwest of england that does rebores and pistons for this engine , the piston that is on the engine looks ok but the barrel is scored it looks like the clip from the gudgeon pin has come loose at some time , is this a common problem on the bantams or is it just bad luck on his part, also he said something about suzuki pistons for the bantam , and how big can the barrel be bored out to remove the gouges in it . as usual any help would be gratefully appreciated when I pass it onto george

regards pete  

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Karl has done good work a number of members bikes. He is just outside Chester off the M56

Mick

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