Please consider registering


— Forum Scope —

— Match —

— Forum Options —

Minimum search word length is 3 characters - maximum search word length is 84 characters

Register Lost password?
sp_Feed sp_PrintTopic sp_TopicIcon
Question about cranks
New User
Site Member
Forum Posts: 4
Member Since:
February 19, 2018
sp_UserOfflineSmall Offline
January 14, 2019 - 10:27 pm
sp_Permalink sp_Print

Does anyone know if there any difference between a B175 crank and a D14 4 crank? thanks

North Dorset
Forum User
Club Member
Forum Posts: 46
Member Since:
September 24, 2018
sp_UserOfflineSmall Offline
January 15, 2019 - 9:33 am
sp_Permalink sp_Print

Yes they are different - B175 had a larger diameter crankpin and the compression plates were crimped in position not secured by rivets as the D14.


the D14 sometimes spat the rivets sometimes wrecking the engine.


The original crank was revised in late 1968 with different rivets,  side plates and flywheels (parts bulletin G54) and in 1970 BSA stopped reconditioning rivetted cranks and supplied ones  repaired and modified to the latest standards (blue top service sheet 256 from April 1970). No details given as to what the latest standard was.


Hopefully your crank will have crimped compression plates.Bantam-B175-letter-to-dealers-18-April-19691.jpgBantam-B175-letter-to-dealers-18-April-19692.jpg

Forum User
Club Member
Forum Posts: 164
Member Since:
April 30, 2012
sp_UserOfflineSmall Offline
January 15, 2019 - 10:11 am
sp_Permalink sp_Print

But if you are asking if complete crankshafts can be swapped between the two models, then yes they can. My B175 engine has been running with a D14 crankshaft for several years now and several thousand miles. The reconditioned B175 crankshaft has now been fitted into my spare D14 engine which is now in my plunger frame off road bike, currently, and hopefully, being made able to go back onto the road.

1951 Bantam D1 125, 1954 Bantam bitsa, 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.

Forum User
Club Member
Forum Posts: 138
Member Since:
August 27, 2013
sp_UserOfflineSmall Offline
January 16, 2019 - 12:34 pm
sp_Permalink sp_Print

Interesting to read that factory letter. As a comparison, £168 in 1968 is the equivalent of £2,750 today. 

Blue Heeler
Forum User
Site Member
Forum Posts: 2139
Member Since:
November 16, 2011
sp_UserOfflineSmall Offline
January 16, 2019 - 1:19 pm
sp_Permalink sp_Print

Very interesting thread. Factory memo states "transfer parts more accurately machined" , my brain actually read that as transfer ports to start with....is that they meant? Was the B175 cylinder also revised in shape externally, a complete new cylinder?

I wish I`d known about my D14`s flywheel cover rivets` crankcase machining capabilities back in the day 🙁    ....subject touched upon on here recently with SpacedMarine`s crank rebuild thread.

Glen, Wish me luck when I put one of my D14s on the market for the £2,750 you mentioned 😉 I bought it for £40 from my Dad in `75, no mate`s/family rates, unfortunately he knew I was often earning £120 a week!  

Forum Timezone: Europe/London

Most Users Ever Online: 223

Currently Online: Lone Wolf, mgraul226, Ringting
10 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

Cornish Rooster: 3314

Anderzander: 3208

bart: 3142

cocorico: 2862

Sprung Chicken: 2650

Mags 1: 2610

David Dale: 2491

Munchkin: 2223

Blue Heeler: 2139

Katj: 2139

Newest Members:


Forum Stats:

Groups: 9

Forums: 46

Topics: 11842

Posts: 101675


Member Stats:

Guest Posters: 518

Members: 3157

Moderators: 1

Admins: 3

Administrators: Piquet, JMD, Rusty Floater

Moderators: xcgb