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Building a C15 trials #395067
09/19/11 11:12 am
09/19/11 11:12 am
Joined: Nov 2001
Posts: 98
Netherlands
J
Jacco van D. Offline OP
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Jacco van D.  Offline OP
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J
Joined: Nov 2001
Posts: 98
Netherlands
To all,

I have a 1965 C15F (USA-model) and am converting it into a trials bike.
1. Is it possible to fit a 18 inch wheel inside the swinging arm?
2. Are the existing front forks suitable? I also have a pair of B40WD forks. I know the are better, but is that really necessary (the are also heavier). And I also have a pair of very late Bantam forks and front wheel. They look quite light/fragile, but are in extremely good condition.
3. Any advice on front wheel size? 19/20/21 inch?
4. Is it possible to use the B40WD wide ratio gears inside my engine.

I don't want to use modern (ie seventies/eighties Jap/Spanish/Italian) parts like forks and wheels and will not modify the frame.

Any advice is highlighy appreciated. Also on other parts.
Its just for fun and to discover if trials riding really is fun or boring.


Kind regards, Jacco


Triumph T100T 1969
Triumph TR6R 1972
Triumph T25T 1971
BSA B25 Fleetstar 1968
Laverda 750SF 1971
TWN Boss 1954
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Re: Building a C15 trials [Re: Jacco van D.] #395069
09/19/11 11:40 am
09/19/11 11:40 am
Joined: Mar 2008
Posts: 131
Wilmington, Delaware USA
O
oldcrow Offline
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oldcrow  Offline
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Joined: Mar 2008
Posts: 131
Wilmington, Delaware USA
Look on the Garage Sale board. Wilf's got a project well on the way, if you can afford the shipping. But I'm sure he can give you some good advice anyway.

Re: Building a C15 trials [Re: Jacco van D.] #395074
09/19/11 12:34 pm
09/19/11 12:34 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

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Joined: Sep 2002
Posts: 7,812
Seattle
Originally Posted By: Jacco van D.
To all,

I have a 1965 C15F (USA-model) and am converting it into a trials bike.
1. Is it possible to fit a 18 inch wheel inside the swinging arm?

Yes, not a problem.

Quote:
2. Are the existing front forks suitable? I also have a pair of B40WD forks. I know the are better, but is that really necessary (the are also heavier). And I also have a pair of very late Bantam forks and front wheel. They look quite light/fragile, but are in extremely good condition.


I think the stock forks are going to limit you on increasing ground clearance...the WD forks aren't much better. I don't know what the rules are or if you're even planning on competing, but it isn't hard to adapt a set of alloy forks from a late B25 or B50. These will be a little bit longer to give you more ground clearance.

Quote:
3. Any advice on front wheel size? 19/20/21 inch?


21 inch, definitely. Larger radius helps you get over obstacles and increases ground clearance. Also, it's hard to find trials tires in any other size. Finally, you can find complete Husquvarna or japanese 21" front wheels with alloy rims and lighweight brakes for pretty cheap.

Quote:
4. Is it possible to use the B40WD wide ratio gears inside my engine.


Yes, it's possible, but it requires quite a bit of work. I've done a similar conversion fitting victor 2nd 3rd and 4th gears to a C15. 1st gear has to be C15 because it incorporates the kick start. Bushings have to be re-honed to fit the larger diameter layshaft. I also added a layshaft drive side needle bearing conversion.

Quote:
I don't want to use modern (ie seventies/eighties Jap/Spanish/Italian) parts like forks and wheels and will not modify the frame.


See above, you will be at a disadvantage...I highly recommend relocating the footpegs rearward and upward. Hard to do that without modifying the frame.

Quote:
Any advice is highlighy appreciated. Also on other parts.
Its just for fun and to discover if trials riding really is fun or boring.



yes, have fun with it...but remember, weight, ground clearance, gearing and riding position will not only make a more competitive trials bike but also will make it much more enjoyable.

Good luck.


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: Building a C15 trials [Re: Jacco van D.] #395085
09/19/11 1:37 pm
09/19/11 1:37 pm
Joined: Mar 2011
Posts: 833
derby england
wak Offline
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wak  Offline
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Posts: 833
derby england
keep it simple use the standard forks a 21" would give the best handling but make sure under full compression theres enought clearence between frame and tyre(bsa went for a 20" on the unit bikes after using 21" on the goldies)wd gears wont all fit as they are of the g type,rupert ratio wrote a great boot about what will fit between the 3 different types of box


BSA lightning
BSA B50MX
TRIUMPH TR6C
BSA BUSHMAN
BSA Gold Star Daytona
BSA Gold Star Scrambler
BSA Rocket Gold Star
BSA C15S
BSA Cyclone
Triumph T120
Triumph T100 Daytona
Triumph 5TA Trials
Triumph T100 Scrambles
Cheney 560 TT
Re: Building a C15 trials [Re: Jacco van D.] #395456
09/21/11 3:09 pm
09/21/11 3:09 pm
Joined: Nov 2001
Posts: 98
Netherlands
J
Jacco van D. Offline OP
BritBike Forum member
Jacco van D.  Offline OP
BritBike Forum member
J
Joined: Nov 2001
Posts: 98
Netherlands
Thanks so far.

Oldcrow: shipping from USA to Rotterdam is a bit to expensive for a complete bike. I also have a freshly powdercoated frame and other parts.

Alex: I have the standard roadster type frame. Will a 18 inch really fit? And also 4 inch wide? I have read in a B40 parts book that a B40 has a different type of swinging arm. Maybe because it has 18 inch wheels???

WAK: I have the Rupert book. But my English isnt that good as I expected. So I wasn't sure if the B40WD WideRatio gears will fit.
Are the skimpy standard forks with inner springs strong enough?
I have an as new 20inch front rim from a B40WD. I will try to use
that one. Any idea if tyres are available?

Well thats for now.

Kind regards, Jacco


Triumph T100T 1969
Triumph TR6R 1972
Triumph T25T 1971
BSA B25 Fleetstar 1968
Laverda 750SF 1971
TWN Boss 1954
Re: Building a C15 trials [Re: Jacco van D.] #395465
09/21/11 3:34 pm
09/21/11 3:34 pm
Joined: Dec 2004
Posts: 9,060
Scotland
kommando Online content
BritBike Forum member
kommando  Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 9,060
Scotland
Alex: I have the standard roadster type frame. Will a 18 inch really fit? And also 4 inch wide?

18" yes but better if you extent the swing arm by an inch or so, 4" no way as the C15 chain run is too close (see comment on B40)

I have read in a B40 parts book that a B40 has a different type of swinging arm. Maybe because it has 18 inch wheels???

Mainly the change was to allow the wider tyre, the sprocket offset also changed so the swing arm cannot be fitted to a C15 without also messing around with the wheel offset.

WAK: I have the Rupert book. But my English isnt that good as I expected. So I wasn't sure if the B40WD WideRatio gears will fit.

As yours is an F you only have to worry about the layshaft inner shaft journal running in a bush, you can use the B44/B25/B40GB gearboxes if you bore it out to suit a needle roller and arrange for a thrustwasher. Even the first gears will fit.

Are the skimpy standard forks with inner springs strong enough?

No, use later B44/B25/B40GB with the rod damper which gives you stiffer forks and 2 way damping. Look for the correct version that matches your propose front wheel.

I have an as new 20inch front rim from a B40WD. I will try to use
that one.

That will fit rod damper forks with screw in spindle.

Any idea if tyres are available?

Yes but only off-road and hard to find.

Also fit longer rear shocks and move the top mounts upwards. Bend the rear frame hoop upwards so the mudguard is higher which allows the longer rear shocks and the 18" wheel to fit. Remove all surplus brackets etc.

Last edited by kommando; 09/21/11 4:00 pm.
Re: Building a C15 trials [Re: kommando] #395493
09/21/11 6:07 pm
09/21/11 6:07 pm
Joined: Nov 2007
Posts: 72
Michigan
dodgeboy57 Offline
BritBike Forum member
dodgeboy57  Offline
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Joined: Nov 2007
Posts: 72
Michigan
While a C15 has proven to be a good trials mount, you might want to see if you can find a B40WD which already has a Trans suited for Trials work and the extra grunt from the 350 is nice to have. An alloy B44 barrel can be cut down and used on the B40 to lower the weight.

Typically, a complete front end from a Rickman 125/250 is fitted. I prefer Yamaha conical front brakes because they work. You will find that a good front stopper is vital for trials work.

One problem with unit BSA trialers is that the engine is offset to the primary or left side. This was done by BSA in order to fit a wider rear wheel. Unfortunately, the bikes tend to want to turn left because of the weight offset and turning right can be a challenge.

For serious trials work you are going to want to change the steering head angle (tuck it in). Sammy Miller (UK) used to offer a nice modified frame and aluminum bits for unit BSAs.

The Otter frame from Faber frames is another trick way to go. Simply install the BSA Unit engine of your choice and ride.

http://www.faberframes.com/

I can help you with frame dimension if you want. I have both an Otter (original, not a repop) and a Sammy Miller BSA frame.

Peg placement is often that of a modern trials bike. As already mentioned, rearward is good. Below the swingarm pivot is good too.

I know a fella that used the dimensions and angles from a Beta to convert a 1966 Ducati Scrambler into a trialer. That bike (and rider) is hard to beat!

PS-typically vintage trials rules limit your suspension to 4" (10.2 cm) rear and 7" (17.8 cm) front.


Last edited by dodgeboy57; 09/21/11 6:11 pm.

45 M20
56 Ariel HS
56 Ariel HT5
(3x)57 B34 "Alloy Clipper" (Tri-Scr-ISDT)
58 A7 Bitza
61 Greeves Hawkstone
63 A10 GSS
63 Greeves MDS
65 Otter B40WD Trls
65 M&M B44(Miller frame/Dick Mann eng)
67 Greeves MX5 ChallengerTT
71 B50/570cc MX
Re: Building a C15 trials [Re: Jacco van D.] #395505
09/21/11 6:57 pm
09/21/11 6:57 pm
Joined: Oct 2007
Posts: 1,275
Nanaimo, B.C. Canada
W
Wilfred Offline
BritBike Forum member
Wilfred  Offline
BritBike Forum member
W
Joined: Oct 2007
Posts: 1,275
Nanaimo, B.C. Canada
Wow.....another C15 trials project. Frame....Swing arms from the early C15 ( 1959 ish ) are longer if you need one but that would just increase wheelbase. My project has longer rear units (13 plus inches) and 1962 B40 roadster front end (also longer than C15 roadster) with a 64 Bantam front wheel (19 inch). Rear wheel is Bantam hub, 18 inch rim with 56 tooth alloy sprocket to fit and 16 tooth gearbox sprocket along with 18 tooth crankshaft sprocket to get the gearing down. With some fabrication, I have installed BSA folding pegs directly below the swing arm pivot as factory bikes. With these frame changes I'll end up with somewhere around 8 inches clearance. 350/18 and 300/19 chen trials tyres. The only thing I haven't done is lower the subframe as in Morley's trials iron book, mainly because I haven't found a suitably shorter oil tank and as the tanks seem to be soldered together have resisted cutting a couple of inches out of one. C15 frame ( engine mounts ) have a closer chain run ala the tire so a B40 frame can be better. I had a couple of B40 frames but the comp rear wheel is really heavy so I opted for the C15 frame and Bantam hubs as the works bikes had and a 350 rear tire. And on it goes but circumstances and age have moved me to sell this project. This is the tough one to sell because of the time and money spent finding bits but that's life. I should be able to survive with only three bikes........If you have any other questions, ask, but I think there are others who know more about these things than I. Cheers, Wilf.


"It's about the ride..."
Re: Building a C15 trials [Re: Jacco van D.] #395540
09/21/11 10:30 pm
09/21/11 10:30 pm
Joined: Aug 2010
Posts: 73
birmingham uk
D
dave thomas Offline
BritBike Forum member
dave thomas  Offline
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D
Joined: Aug 2010
Posts: 73
birmingham uk
Here`s one I built earlier..my `66 C15 F

1, the 18" fits, but clearance is tight and mud can build up. I widened the swing-arm and spindle 1".
2, British forks can be made better although I went for the easy option of some Betors off a Can-Am Bombadier. I`ve got an original HT5 Ariel, and the strength and talent of the guys who threw these things around back in the day never fails to astound me.
3, 21" for grip and tyre choice/availability. You may have clearance problems as stated, depending on your front-end set up?
4, I went with stock C15 gears, and lowered the primary.

You will make life difficult if you do not alter the frame at all, it is a road-bike after all.There are lots of surplus lugs and tubes ( e.g rear foot peg mounts), and riders footpeg position needs sorting.
A lot of the mods used in current pre 65 trials aren`t just there to cheat, they are used by the majority of riders because they work and dont alter the appearance too much.
Good luck with your build

Re: Building a C15 trials [Re: dave thomas] #395554
09/22/11 12:31 am
09/22/11 12:31 am
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,812
Seattle
Dave, that ceefer looks simply delicious. Very nice. I have the can am Betors on my MX bike...doesn't look like a can am front brake though. Is that a rickman hub?


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: Building a C15 trials [Re: Alex] #395572
09/22/11 3:05 am
09/22/11 3:05 am
Joined: Nov 2007
Posts: 72
Michigan
dodgeboy57 Offline
BritBike Forum member
dodgeboy57  Offline
BritBike Forum member
Joined: Nov 2007
Posts: 72
Michigan
Originally Posted By: Alex
Dave, that ceefer looks simply delicious. Very nice. I have the can am Betors on my MX bike...doesn't look like a can am front brake though. Is that a rickman hub?


I'm going to SWAG Wassel hubs.


45 M20
56 Ariel HS
56 Ariel HT5
(3x)57 B34 "Alloy Clipper" (Tri-Scr-ISDT)
58 A7 Bitza
61 Greeves Hawkstone
63 A10 GSS
63 Greeves MDS
65 Otter B40WD Trls
65 M&M B44(Miller frame/Dick Mann eng)
67 Greeves MX5 ChallengerTT
71 B50/570cc MX
Re: Building a C15 trials [Re: Jacco van D.] #395604
09/22/11 9:01 am
09/22/11 9:01 am
Joined: Nov 2001
Posts: 98
Netherlands
J
Jacco van D. Offline OP
BritBike Forum member
Jacco van D.  Offline OP
BritBike Forum member
J
Joined: Nov 2001
Posts: 98
Netherlands
Wilfred:
Can you post a picture of your bike (or e-mail it to me)
I can't afford it to come over to Europe, but I think your bike will look very close to what I want to build. I want a period looking bike with as much BSA bits as possible. No modern (70's/80's) japanese or spanish parts.

To other repliers:
Thanks for the info. Some really good information.
Although I will not use all the information,hints and tips, everything is welcome.

PS: I have the book of Don Morley and Rupert ratio manual.
Nice picture of an early 60's C15 with steel tank inside the Morley book.

Kind regards, Jacco


Triumph T100T 1969
Triumph TR6R 1972
Triumph T25T 1971
BSA B25 Fleetstar 1968
Laverda 750SF 1971
TWN Boss 1954
Re: Building a C15 trials [Re: Jacco van D.] #395659
09/22/11 6:22 pm
09/22/11 6:22 pm
Joined: Aug 2010
Posts: 73
birmingham uk
D
dave thomas Offline
BritBike Forum member
dave thomas  Offline
BritBike Forum member
D
Joined: Aug 2010
Posts: 73
birmingham uk
Alex, the front brake is Can-Am, it was still in drab Green when I got it. Nice brake, the offside part of the hub unscrews to make initial spoke assembly easier I assume?
.
Rear hub is Rickman, eBay purchase, not cheap but came along just at the time I needed one, with Ti spindle and nuts too, though cant notice the weight loss!

Re: Building a C15 trials [Re: Jacco van D.] #395673
09/22/11 7:50 pm
09/22/11 7:50 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
Aaaah, it looks different from the one I have somehow, but then again I used only the brake plate and a Honder drum. I really like that tank. Those buggers aren't cheap and I'd only bang it up so I can't quite justify getting one for my trials iron.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.

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