A A A
Avatar

Please consider registering
Guest

Search

— 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
Centre plug head on D14
Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
1
September 25, 2019 - 9:27 am
sp_Permalink sp_Print

I have a spare centre plug B175 head. Is it worth putting on my D14. Would it make any difference?

Avatar
Bee175
Felixstowe, Suffolk
Top Gear User
Club Member
Forum Posts: 503
Member Since:
April 26, 2014
sp_UserOfflineSmall Offline
2
September 25, 2019 - 9:59 am
sp_Permalink sp_Print

I frankly don't know Ralph.

Is your D14 running ok anyway? Any improvement is going to be minimal. I tend to think that if something is running ok, leave well alone.

Gary.

BSA Bantam B175 1971 and BSA C15 1966

Avatar
JulianS
North Dorset
Top Gear User
Site Member
Forum Posts: 63
Member Since:
September 24, 2018
sp_UserOfflineSmall Offline
3
September 29, 2019 - 6:11 pm
sp_Permalink sp_Print

An interesting factory parts service bulletin dated October 1968 on the D14 and centre plug head.G53-October-1968-D14-centre-plug-head-General-information2.jpg

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
4
September 30, 2019 - 6:45 am
sp_Permalink sp_Print

Interesting.  Do we know what a 70-7799 barrel looks like?. Is this a standard D14 item?

I have a parts list for B175 that lists the barrel as 70-9618, and shows the gasket as 90-1515, presumably a copper gasket?. Mention of only 1 gasket to be used, so does one assume that at some earlier stage there was a recommendation for 2 gaskets to be used on the D14.

Avatar
JulianS
North Dorset
Top Gear User
Site Member
Forum Posts: 63
Member Since:
September 24, 2018
sp_UserOfflineSmall Offline
5
September 30, 2019 - 9:18 am
sp_Permalink sp_Print

90 1515 is 25 thou thick and 70 7967 is 50 thou thick . Below from parts bulletin G48 dated January 1968. G48-January-1968-General-information-D14-head-gasket-RM213.jpg

*** Image attachment removed from post content ***

Ignore the Champion N9Y plug because they changed in back in August that year.

Avatar
Sponge
Lancashire (A chip shop somewhere near Preston)
Top Gear User
Club Member
Forum Posts: 309
Member Since:
November 6, 2016
sp_UserOfflineSmall Offline
6
September 30, 2019 - 11:59 am
sp_Permalink sp_Print

Hi Ralph, 

Having owned several of both machines in my youth I found, through many frustrations),  that the D14/4 with standard (rear plug) head is a fussy engine that overheats with consequent side-effects etc. Reason for this has a lot to do with the relatively high compression ratio and you can see that BSA attempted to remedy the situation with thicker head gaskets etc and then a top end re-think with the new B175 engine.   Also, I found that the D14/4 engine is intolerant  of small irregularities in timing, petroil mixture, carb settings, air temperature etc  - anything that your D14 engine is not happy with will manifest itself as overheating and heat related side-effects.    

I found that the D14/4 engine ran better with two head gaskets fitted, a bit cooler, but then had a tendancy to blow them out. Not difficult to fix but a pain all the same.   I was not aware of the thicker head gasket.  My local BSA dealer advised using two gaskets. 

I did fit a B175 head and gasket to my D14/4 and it made a noticable difference to the engine's manners, because the engine was running cooler, less coughing and banging and 4 stroking on the over-run etc.  There was no discernable loss in performance but also no discernable improvement in power or speed (just better manners).    I eventually got my hands on a Todd head - which made a small difference all around ( more torque, ran cooler and quieter).  

The B175 was a much nicer engine to run because the centre plug head had better heat dissipation, a lower compression ratio and better design (squish band etc).    

So my advise is - if you have a B175 head - fit it and see what it runs like - I doubt you will be disappointed.   Some extra tips though - 

Always make sure you have the tufnol spacer between the carb and the barrel - this prevents the Carb from getting too hot. 

Ensure that your exhaust is in top condition - no excessive carbon or dents etc - this makes a big difference to a D14 engine.     

Ensure that you have the correct inlet tract  ( standard air filter and volumetric tube etc ) these engines seem to be very fussy about changes to their inlet tract and any changes will , once again, lead to overheating and a need to re-tune your carb.  

Hope this helps

Sponge 

Avatar
mikef
Chatham Kent
Club Technical Advisor
Committee
Forum Posts: 1001
Member Since:
September 30, 2011
sp_UserOfflineSmall Offline
7
September 30, 2019 - 3:24 pm
sp_Permalink sp_Print

Hi All.
      We live and learn, as they say. I never knew that BSA ever fitted a straight plug cylinder head to a D14.
Maybe they never actually did. Back in March 1969 I had a D14, brand new, it had the slanted plug head, but of course no idea when it was manufactured.
Anyone else got ideas on this?
It had the usual D14 traits, overheating and pinking when hot. Having said that I was a spotty teenager then and thrashed all heck out of it.
I do remember having to fit two head gaskets though, as even back in 1969 the 0.050" gaskets were not available. Interestingly now I have seen 0.040" head gaskets advertised and 0.060" head gaskets but 0.050" seem unavailable.
I agree with just about everything that Sponge has mentioned above, so won't repeat that.
Mike.

Avatar
mike p5xbx
E-Sussex
Top Gear User
Site Member
Forum Posts: 1742
Member Since:
June 15, 2012
sp_UserOfflineSmall Offline
8
September 30, 2019 - 4:32 pm
sp_Permalink sp_Print

I have a 0.05 head gasket on my D14 dont have any problem with it at all
and it has 150psi compression
but agree that timing and mixture need to be absolutely correct
also helps if you use the correct amount of 2T oil sorryout-a-here

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

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
9
October 1, 2019 - 6:48 am
sp_Permalink sp_Print

Thanks for all your replies, all very helpful.  Mention of the tufnoll carb spacer was interesting, as my bike does not have one, so that needs sorting. 

Given Sponge`s informed answer I think it could be well worth while fitting the B175 head, and this I will do as soon as I can find a 50thou head gasket.

Avatar
mike p5xbx
E-Sussex
Top Gear User
Site Member
Forum Posts: 1742
Member Since:
June 15, 2012
sp_UserOfflineSmall Offline
10
October 1, 2019 - 5:45 pm
sp_Permalink sp_Print

Rex does a 1mm head gasket which is 0.040 maybe near enough

** Please log in to view **

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

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
11
October 1, 2019 - 7:51 pm
sp_Permalink sp_Print

mike p5xbx said
Rex does a 1mm head gasket which is 0.040 maybe near enough

** Please log in to view **

Ta. Just ordered a 1.5mm item, which is 59thou. Thought as I am on +60 piston would err on the bigger side. Also found a 1/4 inch tufnol spacer on ebay and a couple of new carb studs. That may be the reason I don`t have the spacer because the threads are stripped on the first part of the carb studs and I think the spacer may have been removed so that the nuts gripped lower down. I shudder to think how tight the nuts must have been to strip the threads, its a wonder the carb survived.

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
12
October 6, 2019 - 10:21 am
sp_Permalink sp_Print

Well, got all the bits, so had a good session in the garage yesterday.

Took the old head off, and whilst it was off I took the opportunity of setting the ignition timing. Didn`t use a degree disc although I do have one, but set it at 60 thou btdc with a dial gauge. De coked the piston top and fitted the centre plug head and 1.5mm gasket from Rex`s.

Took the carb off and fitted new studs and 1/4" tufnol spacer. A little too thick really, should have gone for the 1/8" version as I had to leave the washers off to get a full thread on the nuts, but I can change that later. whilst the carb was off I changed the slide back to a no3, as the bike had felt to be running weak with the 3.5, but found the reason as it turned out I had fitted the needle on the top groove instead of the middle groove. I am sure I had put it in the middle, but its such a struggle getting it back in with the return spring getting in the way I may have dislodged it. Does anyone have any tips as to doing this easier.

Anyway, the result of all this effort, the bike took longer to start than it used to, and a lot longer to warm up before I could take the choke off, and when I took it down the road it is definitely smoother running with no apparent loss of performance at the top end, but I have now lost all the bottom end torque, and have to rev it and slip the clutch to pull away.

I am going to go out today and put the new 3.5 slide back in, as I suspect that the worn no3 is letting air past and weakening the mixture at the bottom end.

Stay tuned, as they say, 

Ralph.

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
13
October 6, 2019 - 1:55 pm
sp_Permalink sp_Print

Think I found a lot of the problem,20191006_115139.jpg20191006_115210.jpg 

I spent a bit of time rubbing the carb back and forward over a flat file placed on a flat surface. I started out with a 48 thou gap at the worst point, but managed to get it down to less than 2 thou (my smallest feeler gauge wouldn't go under) see below,20191006_121615.jpg20191006_121642.jpg20191006_121821.jpg

Avatar
N.D.James
Swansea
Top Gear User
Club Member
Forum Posts: 161
Member Since:
March 14, 2019
sp_UserOfflineSmall Offline
14
October 6, 2019 - 1:58 pm
sp_Permalink sp_Print

Looks much better but all the little bits make a big difference

 

Nathan 

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
15
October 6, 2019 - 2:07 pm
sp_Permalink sp_Print

Yes, must have been sucking air, there was a thick squidgy cardboard gasket which I removed to fit the tufnol spacer yesterday, with 2 thin paper gaskets. Now its back on and the faces are flat I am sure it is sealing, and it now will pull away from low revs. Still seems a little weak on the first third of the throttle though, so going to invest in a new no3 slide as old one has visible wear and may be letting air past. I will get there in the end.

Avatar
SpacedMarine
Up north
Top Gear User
Club Member
Forum Posts: 747
Member Since:
July 1, 2018
sp_UserOfflineSmall Offline
16
October 6, 2019 - 2:51 pm
sp_Permalink sp_Print

Is that a surface plate or the missus kitchen worktop?🤣🤣🤣

What's 7/16 in mm again?

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3716
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
17
October 6, 2019 - 4:21 pm
sp_Permalink sp_Print

Shouldn't the seal be made by an O ring? The flange of the carb appears to be machined for one.

Avatar
carpetralph
Pontefract
Top Gear User
Club Member
Forum Posts: 129
Member Since:
August 19, 2019
sp_UserOfflineSmall Offline
18
October 6, 2019 - 5:29 pm
sp_Permalink sp_Print

SpacedMarine said
Is that a surface plate or the missus kitchen worktop?🤣🤣🤣  

cocorico said
Shouldn't the seal be made by an O ring? The flange of the carb appears to be machined for one.  

That is a cast iron surface plate Spaced Marine, I am fortunate to have a pretty well equipped workshop, inbetween playing with cars and bikes I am building a half size steam traction engine, and have lathe, milling machine etc. See pics.

Cocorico, correct there is an O ring, but it is very thin, probably no more that 1.5mm thick, and of course half of that sits in the groove, leaving little sticking out, less I think than the distortion in the carb.little-samson.jpg20181025_064232.jpg

sp_PlupAttachments Attachments
Avatar
mike p5xbx
E-Sussex
Top Gear User
Site Member
Forum Posts: 1742
Member Since:
June 15, 2012
sp_UserOfflineSmall Offline
19
October 6, 2019 - 6:11 pm
sp_Permalink sp_Print

carpetralph said

, I am fortunate to have a  

and a Triumph TR2/3 as well smile

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

Avatar
N.D.James
Swansea
Top Gear User
Club Member
Forum Posts: 161
Member Since:
March 14, 2019
sp_UserOfflineSmall Offline
20
October 6, 2019 - 7:01 pm
sp_Permalink sp_Print

carpetralph said

cocorico said
Shouldn't the seal be made by an O ring? The flange of the carb appears to be machined for one.  

That is a cast iron surface plate Spaced Marine, I am fortunate to have a pretty well equipped workshop, inbetween playing with cars and bikes I am building a half size steam traction engine, and have lathe, milling machine etc. See pics.

Cocorico, correct there is an O ring, but it is very thin, probably no more that 1.5mm thick, and of course half of that sits in the groove, leaving little sticking out, less I think than the distortion in the carb.little-samson.jpg20181025_064232.jpg  

What an amazing piece of engineering

I would love to have that in my garage but i might have to work harder for a few more years yet 

Very nice 

 

Nathan 

Forum Timezone: Europe/London

Most Users Ever Online: 223

Currently Online: Blue Heeler, sunny, proth52, Unitminor
18 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

cocorico: 3716

Cornish Rooster: 3290

bart: 3113

Blue Heeler: 2864

Sprung Chicken: 2642

David Dale: 2453

Mags 1: 2329

Piquet: 2288

Munchkin: 2199

nickjaxe: 2070

Newest Members:

_3035

Forum Stats:

Groups: 9

Forums: 48

Topics: 12571

Posts: 109806

 

Member Stats:

Guest Posters: 1476

Members: 2288

Moderators: 0

Admins: 4

Administrators: Bantam-Super, JMD, Springs, Stoo63