BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
  JWood Auction  
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Photo posting tutorial

Member Spotlight
Posts: 79
Joined: September 2005
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
215 registered members (Adam M.), 1,815 guests, and 550 spiders.
Key: Admin, Global Mod, Mod
Newest Members
Brian Ellery, Jon Andrews, Berni Ernst, johnguppy, michael morgan
9955 Registered Users
Top Posters(30 Days)
btour 190
koan58 100
Stuart 88
NickL 66
Popular Topics(Views)
437,160 mail-order LSR
Forum Statistics
Forums33
Topics65,270
Posts632,147
Members9,955
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate This Thread
#629311 - 12/08/15 10:53 am B31 using a T140 piston.  
Joined: Apr 2012
Posts: 253
British Ironwork Offline
BritBike Forum member
British Ironwork  Offline
BritBike Forum member

Joined: Apr 2012
Posts: 253
England
A pal of mine in France wants to use a T140 piston in the B31 motor he is building, to up it to 400cc. He has heard that a barrel spacer is needed, but gets two answers when searching the web, some say 2mm whilst others say 3. Has anybody here had any experience in doing this mod?
Cheers.

Support Your #1 BritBike Forum!
Membership Type! Free
Member
Premium
Member
Premium Life
Member
Vendor
Member
Site
Sponsor
Recognition No Premium Member Premium Life member (5 years) Vendor Member Site Sponsor Membership
Post commercial threads No No No Yes Yes
Custom title No Yes Yes Yes Yes
Upload avatar & photos No Yes Yes Yes Yes
Link avatar & photos Yes Yes Yes Yes Yes
Private Message Storage: 10 100 100 100 100
Length of signatures 255 600 600 600 600
Removes this very advert island between post 1&2 No Yes Yes Yes Yes
Price Free $12.90/year $105.00 No End
$55.00/5 years
$210.00/year
($17.50/month)
Email
Click on button >>
  Premium Member Premium Life member Vendor Member Site Sponsor Membership
#629351 - 12/08/15 3:29 pm Re: B31 using a T140 piston. [Re: British Ironwork]  
Joined: Apr 2002
Posts: 962
beezageezauk Offline
BritBike Forum member
beezageezauk  Offline
BritBike Forum member

Joined: Apr 2002
Posts: 962
North East England
I did this modification to my B31 back in 2000 and have covered many thousands of trouble free miles with it since. I've also converted quite a few engines for friends without any negative feedbacks.

I've always used a 2mm spacer (decompression plate) but must admit that I showed concern when I first fitted Goldie touring cams with the high compression T140 piston. However, there was no need for me to worry as nothing fouled and that engine has been running fine for quite some time now.

So, I would suggest that a 2mm spacer should be fine but once the job is done I would advise to turn the engine over very slowly before trying to fire it up, just in case!!

Beezageezauk.

#629358 - 12/08/15 4:08 pm Re: B31 using a T140 piston. [Re: British Ironwork]  
Joined: Apr 2012
Posts: 253
British Ironwork Offline
BritBike Forum member
British Ironwork  Offline
BritBike Forum member

Joined: Apr 2012
Posts: 253
England
Thanks for that, I'll let him know.

#629360 - 12/08/15 4:19 pm Re: B31 using a T140 piston. [Re: British Ironwork]  
Joined: May 2013
Posts: 4,533
Allan Gill Offline
Allan Gill  Offline



Joined: May 2013
Posts: 4,533
Rotherham - S. Yorkshire
You can always put some strips of plasticine on the crown, the valves will cut an impression and you will know exactly how much clearance you have.

( I can vouch for Ray's bike)


beerchug
#629367 - 12/08/15 5:35 pm Re: B31 using a T140 piston. [Re: beezageezauk]  
Joined: May 2011
Posts: 432
GS DAVE Offline
BritBike Forum member
GS DAVE  Offline
BritBike Forum member

Joined: May 2011
Posts: 432
england
Did you use 2 base gaskets or just sealant ?

#629544 - 12/10/15 6:21 am Re: B31 using a T140 piston. [Re: GS DAVE]  
Joined: Apr 2002
Posts: 962
beezageezauk Offline
BritBike Forum member
beezageezauk  Offline
BritBike Forum member

Joined: Apr 2002
Posts: 962
North East England
Originally Posted By GS DAVE
Did you use 2 base gaskets or just sealant ?


If I'm converting an engine for somebody else I ask if they have a preference and act according to their wishes.

I generally don't use gaskets in my own engines. Instead, I use "Granvilles Instant Gasket". This is a specially formulated silicon based substance that comes in a squeeze tube. It's available in various colours, including clear (my preference). Most of my riding is doing long distances and this stuff is ideal if I need to undertake repairs on the roadside or on a campsite miles away from anywhere. With no worries of damaging paper gaskets or trying to make replacements. I'm just more careful of using it around oilways.

I put a smear of this each side of the decompression plate.

Beezageezauk.

#629580 - 12/10/15 2:03 pm Re: B31 using a T140 piston. [Re: British Ironwork]  
Joined: Aug 2015
Posts: 931
Andy Higham Online content
BritBike Forum member
Andy Higham  Online Content
BritBike Forum member

Joined: Aug 2015
Posts: 931
Bolton Lancs UK
Before you do anything decide what compression ratio you require.
Temporarily assemble barrel head and piston onto the engine, position with the spark plug hole uppermost.
Turn engine until piston is at TDC on compression stroke, or leave pushrods out
Using a graduated syringe fill the combustion chamber with thin oil until it reaches half way up spark plug hole and note exactly how much oil has been added
Your compression ratio is the cylinder capacity + the quantity of oil / the quantity of oil.


1955 BSA B31 400cc "Stargazer"
1962 Greeves 200cc "Blue Meanie"
1962/67 Greeves 350cc
1967 Greeves 360cc Challenger
1984 Suzuki GSX1100 EFE "Sorcerers Apprentice"
Modified Nu-Trak GM500cc sprint/LSR bike "Deofol"
2003 Aprilia RSV Mille "Lo Stregone"
#629581 - 12/10/15 2:17 pm Re: B31 using a T140 piston. [Re: British Ironwork]  
Joined: Dec 2004
Posts: 8,887
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,887
Scotland
Andy, why 1/2 way up the spark plug hole, I would have thought it would be just as the oil entered the hole and touched the threads.

#629586 - 12/10/15 3:01 pm Re: B31 using a T140 piston. [Re: kommando]  
Joined: May 2011
Posts: 432
GS DAVE Offline
BritBike Forum member
GS DAVE  Offline
BritBike Forum member

Joined: May 2011
Posts: 432
england
Due to the void between the insulator and the threaded body.
Ie a near representation of volume when the plug is fitted.


Moderated by  Allan Gill, Jon W. Whitley 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.409s Queries: 15 (0.080s) Memory: 0.8526 MB (Peak: 1.0444 MB) Zlib disabled. Server Time: 2017-11-21 09:44:47 UTC