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Monobloc 375 Carb issues and advice!
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Neil wood
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November 14, 2019 - 10:01 pm
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I am doing up a D1 that has been fitted with the later D7 175cc engine! The carb needs some work and I believe it to be a mono block 375/16 carb??? These are the numbers that are stamped on the flange.
looking at most of the sites this seems to be incorrect in numbers! What is the difference between a 375/31 and a 375/16?

i need to buy some new needles etc and want to know if it’s worth persevering with this carb or if I need to replace it with a more original item.

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Stoo63
GLASGOW
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November 14, 2019 - 11:24 pm
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Hi Neil, and welcome to the Forum.

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. It's a good idea to include 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. Photos help greatly - there's a 1mb limit in image size -  and would definitely be an advantage in your case, if you need members to identify what bits you've got from when. Help here ** Please log in to view ** it may seem difficult  to begin wit but once you get the hang of it.....   

Doubtless some of the D7 boys will be along shortly to give you plenty of advice but this should help with ID in the meantime ** Please log in to view **

Looks like your "16" came off an Enfield Crusader perhaps..

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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Stoo63
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November 14, 2019 - 11:45 pm
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......and if you're ordering parts from Burlen UK , the Amal stockists, don't forget to order a FREE Amal catalogue - it's packed full of info and diagrams and will help as well. 

'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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sunny
Norfolk
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November 15, 2019 - 9:46 am
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i  woud  try  it  first     after   cleaning       & dont forget   the  two  pilot   holes    one  in  each  part   of  the  body   bits  arnt  cheap   & 31    & 16  is the  slide  size    i  think

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stubaker58
Sunny Felixstowe
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November 15, 2019 - 11:35 am
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Hi Neil

my understanding of the Monobloc is that the first number relates to the model of the carb ie 375. This is correct for a D7 and relates to the carb body. The second number is the specification for a particular motorcycle and relates to the variables within the carb eg jets, slide, needle etc.

You can use the carb but will need to check that the internals are the correct spec.  These parts are not cheap and you run the risk of the actual body of the carb being worn which really means replacing it as even with new jets etc it will not run properly. New monoblocs are available and Burlen will supply them set up for a D7.

In your position I’d check the wear on the carb slide/body look at the jets, replacing them if incorrect and see how things went, others would plump straight for a new carb and bypass the possibility of spending out for jets etc and still having a carb that doesn’t work!

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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Stoo63
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November 15, 2019 - 1:27 pm
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Hi Neil, having a brief look on the Burlen site, it looks like a new main jet, which is the only one different on the table above will cost you £4.09 inc vat. A complete new carb specifically for a D7, when in stock, will cost you around £170. Personally, I'd be checking the number on my main jet and, if I needed, ordering a new 140 main jet(as well as FREE catalogue) If it works - great! If not - you've spent a fiver. The jet may already have been changed over by the previous owner. Was the bike ever running with the D7 engine in? Does it look like that was the carb that was on it if it did run? If you can upload any pics that would be really helpful.

Cheers

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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chickensoup
Bolton, Greater Manchester
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November 15, 2019 - 8:49 pm
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Hi Neil,

My D7 has a 375/9 carb. Think it's off an Excelsor Consort from the late 50's. It has the correct jets and needle for a 1966 D7, and it runs great.

I would persevere with your carb for the time being. When your ready to try and start your engine, maybe a fellow, local club member could give you the loan of a correct and trusty carb, once your engine is running well, then try your carb and see if there is any difference.

Good luck... Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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rousers44
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November 24, 2019 - 10:07 pm
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The 375/16 is from an Enfield crusader and the /31 is from a Bantam D7 175 1957/65 

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Sprung Chicken
Glasgow,Scotland
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November 25, 2019 - 12:29 am
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search for ** Please log in to view **. I did a video some years ago on stripping and rebuilding.

Hope this helps...

Dougie;Glasgow ;Scotland.
1955 D1, 1970 B175

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Neil wood
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November 25, 2019 - 6:17 am
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Thanks,

it seem that there is no such thing as “standardisation” when it comes to a Banatm!

This weekend I will strip down and see what I’ve got! I have ordered the book and 140 main jet so if it’s different I can swop it for the correct one.

catch up soon. 

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