BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorThe Bonneville ShopBritBike Sponsor
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments.
Buy BritBike staff a coffee
Buy BritBike's staff a coffeeStill here since 1996 serving BritBike enthusiasts..
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Member Spotlight
headlamp
headlamp
the south
Posts: 139
Joined: April 2004
Show All Member Profiles 
Newest Members
Argos parts, Mr. Bean, rudi, Derek, Psychorider
10862 Registered Users
Top Posters(30 Days)
franko 167
DavidP 69
reverb 61
NickL 53
Popular Topics(Views)
1,019,344 mail-order LSR
a word from..
Forum Statistics
Forums34
Topics67,800
Posts680,417
Members10,862
Most Online14,755
May 5th, 2019
Who's Online Now
45 registered members (Al Eckstadt), 433 guests, and 864 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Technical help needed on big bore B33 #782238 08/22/19 4:19 pm
Joined: Aug 2019
Posts: 5
M
myB33 Offline OP
BritBike Forum member
OP Offline
BritBike Forum member
M
Joined: Aug 2019
Posts: 5
Hi Everyone, its my first time posting on the site, so go easy on me! I'm hoping that someone can offer me some advise on valve timing on my BSA B33.
It would be rude of me not to introduce myself and give a bit of background to the question I'm asking.
I bought my 1948 B33 roughly two years ago, it was an upgrade to my earlier & first British bike which was a C15 Star.
When originally bought the B33 was in tatty condition, mismatched & in a rough running order, with a little work i kept it running and rode it regularly until a problem of oil being blown out of the engine breather forced me take it off the road to remedy the fault, it had got so bad that i connected a hose to the breather and vented straight back into the oil tank!
Upon engine strip down i was surprised to find the problem was a broken exhaust valve guide, the exhaust rocker housing was chock a block with carbon, blocking the oil drain, which no doubt pressurized the engine causing the oil to be expelled from the breather! Once the engine was stripped, i found the piston was ok but the bore was badly pitted and a re bore was out of the question as the piston was on the final size available.
I found that the engine had goldie touring cams 2448, 2450 & head had been roughly ported, which explained why it was so much quicker than you would expect from a iron head B33 ! To cut a long story short, i had the barrel re bored and shortened to take a bigger 90mm wiseco cast piston, I've had the original B33 crank rebuilt with a shorter con rod with bronze bush for the gudgin pin, new valves, seats and such, I've installed a light weight modified jap clutch & larger cush drive sprocket, all is going well, but would like some advise on valve timing & ignition timing please, especially the valve timing with the goldie cams, this was a common upgrade years back so im hoping someone can help me,so i can get the bike running and back on the road. thanks

Support Your #1 BritBike Forum!

Check out British motorcycles for sale:
British Motorcycles on e-Bay UK
British motorcycles on e-Bay North America
Re: Technical help needed on big bore B33 [Re: myB33] #782258 08/22/19 8:06 pm
Joined: Jun 2019
Posts: 34
M
Motolab Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Jun 2019
Posts: 34
Hi, welcome,

In my opinion, B33’s do not cope very well with “goldie style“ internals.
The B33 is regarding thermal Design & behavior not meant for more power than basic (at least in petrol) the big Fin also not, so let alone the small Fin you have..

Every engine i know of witch is modified, breaks down because of the extra heat.. (and i know a few)

So my advise, put standard cams in it.. and compresion not higher than 7.5:1 or max 8 maybe.. but be careful there..
Timing of the cams is in both forms, standard... the pinion and all the cams are marked... stay with that...

It is an old slogger, respect it that way and it will run fine, tune it, it will break...
If you want to go quicker, buy an all alloy engine


Harold
BSA: M20 ‘40 M21,B31 ‘55 B33 ‘54, ZB34GS ‘49
Triumph 5T ‘49 + T100 speedkit
Sunbeam S7 ,48
Moto Guzzi LeMans ‘79
BMW R51/3 ‘ 51, R100GS ‘89
Re: Technical help needed on big bore B33 [Re: Motolab] #782312 08/23/19 10:35 am
Joined: Aug 2019
Posts: 5
M
myB33 Offline OP
BritBike Forum member
OP Offline
BritBike Forum member
M
Joined: Aug 2019
Posts: 5
Thanks Motolab for the input, I'm aware an increase in compression can cause the engine to run hotter, i don't think ive increase compression to that extent, one benefit of using the forged piston is that they do handle the heat much better than the alloy originals, I'm going to to run it with a colder plug, and the mixture slightly on the rich side, i don't intend racing the poor thing, these plodders dont like high rpm.. I just want a little more pop, low end torque.
Your deference to standard timing for the goldie cams is interesting, as it appears that these cams give a more abrupt lift compared to the originals which look more gradual, so i assumed timing of these cams would be an issue?
your thoughts would be welcome. thanks

Re: Technical help needed on big bore B33 [Re: myB33] #782346 08/23/19 4:27 pm
Joined: Aug 2015
Posts: 1,436
A
Andy Higham Offline
BritBike Forum member
Offline
BritBike Forum member
A
Joined: Aug 2015
Posts: 1,436
I built a 400cc B31 using a T140 piston, I used DBD34 Clubman Vernier cams timed at IN 100 deg Lobe centre and EX 102 deg lobe centre 32mm Mikuni flat slide carb and Pearson crank with Carillo rod.
It Idled well, was tractable and when given a handful really took off, 85MPH in a standing start mile and still accelerating (measured using TAG Heuer equipment on a private runway). It was very smooth and I could still see a clear image in the mirrors.
It now has alloy DBD34 head and barrel


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: Technical help needed on big bore B33 [Re: Motolab] #782350 08/23/19 5:01 pm
Joined: Jun 2019
Posts: 34
M
Motolab Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Jun 2019
Posts: 34
Originally Posted by myB33

Your deference to standard timing for the goldie cams is interesting, as it appears that these cams give a more abrupt lift compared to the originals which look more gradual, so i assumed timing of these cams would be an issue?
your thoughts would be welcome. thanks



Originally Posted by Motolab

Timing of the cams is in both forms, standard... the pinion and all the cams are marked... stay with that...



Maybe i have should said, stay with the standard camtiming..... goldie cams are also marked... stay with that standard timing is what i meant..

BUT... B31’s can handle goldie touring cams, even with 50cc more, but they are not 500cc’s. B31’from 440cc on and B33’s handles tuning not so very well in my opinion, every body knows “big” stories, i have done that, seen this... well maybe tuning works on alcohol fueled B33’s but not on the hotter running petrol imho

As temperatures are only rising these day’s expect trouble in the summer...


If it breaks down, you are the one to pay the money for repair...


Harold
BSA: M20 ‘40 M21,B31 ‘55 B33 ‘54, ZB34GS ‘49
Triumph 5T ‘49 + T100 speedkit
Sunbeam S7 ,48
Moto Guzzi LeMans ‘79
BMW R51/3 ‘ 51, R100GS ‘89
Re: Technical help needed on big bore B33 [Re: Andy Higham] #782373 08/23/19 9:13 pm
Joined: Aug 2019
Posts: 5
M
myB33 Offline OP
BritBike Forum member
OP Offline
BritBike Forum member
M
Joined: Aug 2019
Posts: 5
Thanks Andy, an interesting post!

Re: Technical help needed on big bore B33 [Re: Motolab] #782374 08/23/19 9:18 pm
Joined: Aug 2019
Posts: 5
M
myB33 Offline OP
BritBike Forum member
OP Offline
BritBike Forum member
M
Joined: Aug 2019
Posts: 5
'Maybe i have should said, stay with the standard camtiming..... goldie cams are also marked... stay with that standard timing is what i meant'

Thanks for the clarification, much appreciated.

Re: Technical help needed on big bore B33 [Re: myB33] #782443 08/24/19 1:25 pm
Joined: Dec 2004
Posts: 10,068
kommando Online Content
BritBike Forum member
Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 10,068
BSA Service sheets

https://www.britishonly.com/tech/manuals/bsaservicesheets.asp


you download the sheets that cover the engine, frame , brakes , suspension etc that your bike is fitted with eg B series engine and also any Gold Star sheets.

Re: Technical help needed on big bore B33 [Re: myB33] #782518 08/25/19 8:17 am
Joined: May 2004
Posts: 4,107
B
BSA_WM20 Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: May 2004
Posts: 4,107
The only person I know with a big bore B33 & a bigger bore M20 is Ian Wright.
He inhabits the WM20 forum.
His bike seems to run quite fine as he is always popping off to somewhere in Europe on it.
Now that he has retired he has become very generous with technical information so pop over & repeat this thread over there.
wm20 forum


Bike Beesa
Trevor
Re: Technical help needed on big bore B33 [Re: BSA_WM20] #782691 08/26/19 10:24 pm
Joined: Aug 2019
Posts: 5
M
myB33 Offline OP
BritBike Forum member
OP Offline
BritBike Forum member
M
Joined: Aug 2019
Posts: 5
Thanks Trevor for the heads up, very interesting site with lots of useful information.

Re: Technical help needed on big bore B33 [Re: myB33] #782718 08/27/19 2:38 am
Joined: May 2004
Posts: 4,107
B
BSA_WM20 Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: May 2004
Posts: 4,107
The bulk on here are Unit engine owners with a smattering of Goldies and the odd preunit A, B or M owners.
I gather you have searched the site for "over bored & big bore & larger bore "
Ian who is OS at the moment occasionally does a run of oversized pistons for M & B series bikes so give it a day or two.
Responders do so in line with the speed their bikes run.


Bike Beesa
Trevor

Moderated by  Allan Gill, Jon W. Whitley 

Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.3