BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
JWood Auction JRC Engineering dealers 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
MikesClassics
MikesClassics
Queensland, Australia
Posts: 83
Joined: November 2016
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
210 registered members (68 royalstar tony), 1,774 guests, and 585 spiders.
Key: Admin, Global Mod, Mod
Newest Members
Simon.Holyfield, Bushcreature, Doug Valley, tim_v7, BosBSA
10032 Registered Users
Top Posters(30 Days)
Lannis 144
kommando 102
Stuart 65
Popular Topics(Views)
476,308 mail-order LSR
Forum Statistics
Forums33
Topics65,711
Posts635,140
Members10,032
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate Thread
BSA C15 - Largest Oversized Piston Possible #287583
12/06/09 9:59 am
12/06/09 9:59 am
Joined: Nov 2007
Posts: 132
England
C
ceefer Offline OP
BritBike Forum member
ceefer  Offline OP
BritBike Forum member
C
Joined: Nov 2007
Posts: 132
England
I have been working on my C15's brakes and forks for ages and finally I am getting near to working on the engine. I have been reading the advice that I have received from this site before on increasing the performance of the engine, trying to settle upon the most sensible modifications, short of fitting a larger motor altogether.

One suggestion has been to fit a larger Triumph piston to increase the capacity and the compression at the same time. I am coming around to this idea as being most sensible and cost effective.

My question is: what is the largest overbore that a C15 can take and will a Triumph 650cc Tiger piston fit? Does anyone know whether 10:1 Triumph piston will give 10:1 in the C15 or does it alter dramatically? I seem to recall reading somewhere or other that these bikes can be taken out to about 320cc, but I might have imagined this. Any suggestions?

Thank you.

James.


James Alford
Copper Water Features and Garden Ornaments
www.craftedcopper.co.uk
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
Re: BSA C15 - Largest Oversized Piston Possible [Re: ceefer] #287697
12/06/09 11:44 pm
12/06/09 11:44 pm
Joined: Dec 2002
Posts: 3,235
arkansas
L
leon bee Offline
BritBike Forum member
leon bee  Offline
BritBike Forum member
L
Joined: Dec 2002
Posts: 3,235
arkansas
James: I've no idea, but I'm another of those guys hates to see a question never responded to. Have you seen this nice website? http://www.bsa-c15.org.uk/

Last edited by leon bee; 12/06/09 11:45 pm.
Re: BSA C15 - Largest Oversized Piston Possible [Re: leon bee] #287701
12/07/09 12:33 am
12/07/09 12:33 am
Joined: Feb 2003
Posts: 2,884
Ohio
R
Rickman Offline
BritBike Forum member
Rickman  Offline
BritBike Forum member
R
Joined: Feb 2003
Posts: 2,884
Ohio
Hmmm,
You might also look at the thread "BSA's for daily use", or something like that?
Maybe those guys over there might have some suggestions?

I've heard of other alternative uses, with parts from other various manufacturers.... It just takes research... Maybe some sort of alterations...

Re: BSA C15 - Largest Oversized Piston Possible [Re: Rickman] #287783
12/07/09 4:20 pm
12/07/09 4:20 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

BritBike Forum member
Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,812
Seattle
A .040" over (70 mm) triumph 500 piston is about as big as I'd want to go. The skirt gets pretty thin at this point. Daytona pistons will give you about 9:1. Remove 1 mm from the head or barrel and you get 10:1 and a better squish.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: BSA C15 - Largest Oversized Piston Possible [Re: Alex] #287791
12/07/09 5:26 pm
12/07/09 5:26 pm
Joined: Aug 2001
Posts: 1,839
British Columbia
hh Offline
BritBike Forum member
hh  Offline
BritBike Forum member
Joined: Aug 2001
Posts: 1,839
British Columbia
If you sleeve the cylinder, you can use the low compression 650 piston.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
Re: BSA C15 - Largest Oversized Piston Possible [Re: hh] #287794
12/07/09 5:32 pm
12/07/09 5:32 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

BritBike Forum member
Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,812
Seattle
Originally Posted By: hh
If you sleeve the cylinder, you can use the low compression 650 piston.


I believe that's the case for a B25? Dont see how that would change things for a c15..


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: BSA C15 - Largest Oversized Piston Possible [Re: Alex] #287799
12/07/09 5:55 pm
12/07/09 5:55 pm
Joined: Aug 2001
Posts: 1,839
British Columbia
hh Offline
BritBike Forum member
hh  Offline
BritBike Forum member
Joined: Aug 2001
Posts: 1,839
British Columbia
Alex, is the crankcase spigot hole too small for a bigger sleeve? I've seen Commando barrels with a sleeve that poked through the fins, so I don't think that would necessarily be a problem. I could be confused with the B25.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
Re: BSA C15 - Largest Oversized Piston Possible [Re: hh] #287890
12/08/09 3:47 am
12/08/09 3:47 am
Joined: Jun 2002
Posts: 913
Jaffrey, NH, USA
Peter Quick Offline

Sponsor
Peter Quick  Offline

Sponsor
Joined: Jun 2002
Posts: 913
Jaffrey, NH, USA
James, There are a bunch of things you could do to increase power. What is the year and type of motor? The scrambler motors had hotter cams then the road version. They had a different head with a larger intake valve and a bigger choke to take a bigger carb. If you have an early C15 road type bike, not a SS80 you might want to be careful about too much compression. The crank design went through at least 3 improvements to handle more power and compression. If you really want to have high 10:1 compression you might want to consider replacing your timing side bush with a roller conversion. If you have an old bushed crank don't do anything until you replace it with a newer better caged roller bearing one. I guess it all depends on what motor, head, carb you are starting with. A bigger bore and higher compression need to be complimented with the other items I mentioned otherwise wasted effort or blown up motor. Peter


check out: www.bsaunitsingles.com
2500 BSA part numbers with inventory in stock just for the unit singles!
Re: BSA C15 - Largest Oversized Piston Possible [Re: Peter Quick] #287909
12/08/09 8:23 am
12/08/09 8:23 am
Joined: Nov 2007
Posts: 132
England
C
ceefer Offline OP
BritBike Forum member
ceefer  Offline OP
BritBike Forum member
C
Joined: Nov 2007
Posts: 132
England
Thank you for the advice: as usual, so helpful.

Alex: thank you for the recommendations on the piston and skimming. This is exactly what I was trying to find out. Do you think that a 650 Triumph piston would be suitable as I have been offered some!

PeterQ: I have a C15F side points engine. It has a roller bearing big-end and the needle-bearing conversion on the timing side. I have already fitted a different cam, larger carb, inlet valve and opened out the inlet ports.

Other suggestions that I have received include changing the entire top end for one from a B25. This does need the barrel spigot to be reduced and a plate (1/4", I think) under the barrel to allow it all to fit. This seems the "obvious" route to take, but having carried out the other work to the head, I am undecided.

I need to consider carefully the most sensible option for my purpose which is to add a little more sparkle to the performance for road use.

Regards,

James.

Last edited by ceefer; 12/08/09 8:35 am.

James Alford
Copper Water Features and Garden Ornaments
www.craftedcopper.co.uk
Re: BSA C15 - Largest Oversized Piston Possible [Re: ceefer] #288355
12/11/09 8:31 am
12/11/09 8:31 am
Joined: Nov 2007
Posts: 132
England
C
ceefer Offline OP
BritBike Forum member
ceefer  Offline OP
BritBike Forum member
C
Joined: Nov 2007
Posts: 132
England
Decison reached: I will look out for a 500 Daytona piston and try that along with the 1mm skim.

Next step - searching for a piston.

Regards,

James.


James Alford
Copper Water Features and Garden Ornaments
www.craftedcopper.co.uk
Re: BSA C15 - Largest Oversized Piston Possible [Re: ceefer] #288371
12/11/09 10:23 am
12/11/09 10:23 am
Joined: May 2006
Posts: 509
melbourne, australia
7
76degree-triumph Offline
BritBike Forum member
76degree-triumph  Offline
BritBike Forum member
7
Joined: May 2006
Posts: 509
melbourne, australia
Gday James, I reckon I have a pair of used (never seized) 69 mm pistons from my '69 T100c. If you pay for postage they are yours. tribsa70@hotmail.com if you are interested.
Chris.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
Re: BSA C15 - Largest Oversized Piston Possible [Re: 76degree-triumph] #288544
12/12/09 9:39 am
12/12/09 9:39 am
Joined: Nov 2007
Posts: 132
England
C
ceefer Offline OP
BritBike Forum member
ceefer  Offline OP
BritBike Forum member
C
Joined: Nov 2007
Posts: 132
England
Chris. Thank you. I shall e-mail you.

Regards,

James.


James Alford
Copper Water Features and Garden Ornaments
www.craftedcopper.co.uk
Re: BSA C15 - Largest Oversized Piston Possible [Re: ceefer] #292227
01/04/10 4:41 pm
01/04/10 4:41 pm
Joined: Oct 2008
Posts: 38
Houston, Texas (West end of th...
Lucky Strike Offline
BritBike Forum member
Lucky Strike  Offline
BritBike Forum member
Joined: Oct 2008
Posts: 38
Houston, Texas (West end of th...
76degree-triumph,

Since you have a pair of pistons, and ceefer needs but one, may I ask for the other for my 1960 C15??


Fast. Cheap. Good. Pick any two....

1973 T140V
1960 BSA C15

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
Powered by UBB.threads™ PHP Forum Software 7.6.1.1