Fork mods

Here you can talk about all kind of TECH for the B50 B44 B25 And Other BSA unit Singles

Moderator: minetymenace

fastharry
>120
>120
Posts: 123
Joined: Tue Dec 14, 2010 9:40 am
Location: Leicester England
Flag: England

Fork mods

Postby fastharry » Thu Dec 05, 2013 7:42 pm

I have recently bought a B50mx, i have read somewhere that there are modifications to the front forks that can make a great improvement. Has anyone got any idea what they are,

User avatar
minetymenace
Gerry1
Gerry1
Posts: 6679
Joined: Wed May 26, 2004 1:00 am
Location: Between Reading and Newbury, England
Flag: England
Contact:

Re: Fork mods

Postby minetymenace » Fri Dec 06, 2013 2:05 am

<135 to the forum fastharry.

I'm going to move this to "Tech" as is is more of a technical question rather than a write up (don't be put off, it is what I do)

Would you also update your profile and let us know where you are please?
Abyssinian Wire-Haired Tripehounds Gnash.

User avatar
gunnag
>720
>720
Posts: 734
Joined: Fri Oct 01, 2004 9:32 am
Location: farnham surrey
Flag: Great Britain

Re: Fork mods

Postby gunnag » Fri Dec 06, 2013 8:55 pm

Not sure about MX bikes but certainly one improvement for BSA forks is to change the springs to progressive types. This will help the forks to be more sensitive on smoother surfaces, absorb shocks on rougher surfaces an prevent bottoming out/diving. You can get progressive springs from SRM, Hagon and other BSA suppliers.

The other modification is to change the damper valves to improve compression and rebound damping. This is more of a specialized modification which may need an expert in suspension like Maxton though it may be possible to do on a diy basis using Racetech cartridge emulator damping see http://racetech.com/HTML_FILES/DampingRodForks.HTML

fastharry
>120
>120
Posts: 123
Joined: Tue Dec 14, 2010 9:40 am
Location: Leicester England
Flag: England

Re: Fork mods

Postby fastharry » Fri Dec 06, 2013 9:52 pm

Yes, progressive springs are one of the mods i have in mind, i was hoping someone might have had a positive experience to pass on, I did talk to maxton and i was a bit shaken at the price of a revalve on what is a fairly simple fork design, £450 + vat at 20%, im hoping some one has tried things like the raceteck valves and give us there veiws.

User avatar
roadplough
<1100
<1100
Posts: 1189
Joined: Sat Nov 27, 2004 12:25 am
Location: Noosa, Australia

Re: Fork mods

Postby roadplough » Fri Dec 06, 2013 11:32 pm

When I bought a pair of legs last year the seller mentioned a damping mod, supposed to be a vast improvement.
I didn't quite get what he meant so he sent some pics but I still don't understand and can't offer any further info but here are the photos:
T160.jpg
T160
No idea of the relationship of the T160 legs to these next 2 pics:
DamperMod.jpg
DamperModd.jpg

Some one else may be able to explain.
Another (easy) mod is to replace the damper o-rings with the split metal type which along with progressive springs I got from that mob in New Zealand.

User avatar
gunnag
>720
>720
Posts: 734
Joined: Fri Oct 01, 2004 9:32 am
Location: farnham surrey
Flag: Great Britain

Re: Fork mods

Postby gunnag » Sat Dec 07, 2013 1:26 am

My understanding is that the Racetech cartridge emulators provide much finer and accurate control of compression and rebound damping as commonly found on modern bikes and therefore give much better control of the ride. I believe the cartridge emulators can be purchased and retro fitted to some BSA's, but I dont know how its done.

Regarding the progressive springs, I have a set fitted on my 68 A65 and they have made a big improvement in the ride quality, so I can recommend them. I have also fitted a pair of Hagon adjustable 2810 shocks which are also very good and improved the rear end damping no end, these are similar to the old koni dial a ride dampers.

Norman_John
>140
>140
Posts: 158
Joined: Tue Jul 08, 2008 5:16 pm
Location: Nuneaton, England

Re: Fork mods

Postby Norman_John » Sat Dec 07, 2013 9:49 am

The same for me as Gunnag - progressive springs in the otherwise bog standard forks on my 1968 B44 made me happy enough to looking for modern forks I could bolt on.
John

fastharry
>120
>120
Posts: 123
Joined: Tue Dec 14, 2010 9:40 am
Location: Leicester England
Flag: England

Re: Fork mods

Postby fastharry » Sat Dec 07, 2013 7:45 pm

Fantastic, just what i was after. Can you tell me the make of the the progressive springs as there are many out there, Thanks again.

Norman_John
>140
>140
Posts: 158
Joined: Tue Jul 08, 2008 5:16 pm
Location: Nuneaton, England

Re: Fork mods

Postby Norman_John » Sat Dec 07, 2013 11:10 pm

If you can make your way over to Nuneaton from Leicester I have an unused pair in the cupboard you can have... PM me?
John

User avatar
minetymenace
Gerry1
Gerry1
Posts: 6679
Joined: Wed May 26, 2004 1:00 am
Location: Between Reading and Newbury, England
Flag: England
Contact:

Re: Fork mods

Postby minetymenace » Sun Dec 08, 2013 12:16 am

Leicester to Nuneaton is less than 20 miles and most of it is motorway!
Abyssinian Wire-Haired Tripehounds Gnash.

fastharry
>120
>120
Posts: 123
Joined: Tue Dec 14, 2010 9:40 am
Location: Leicester England
Flag: England

Re: Fork mods

Postby fastharry » Mon Dec 09, 2013 12:22 am

I certainly will. Its the A5 for me.

blaise
>180
>180
Posts: 187
Joined: Thu Dec 13, 2012 10:22 pm
Location: San Carlos, CA. USA
Flag: United States of America

Re: Fork mods

Postby blaise » Wed Feb 05, 2014 12:58 am

I am scheming to make some modifications to the front forks of my 1969 BSA B25 (B44 motor), as I am unimpressed with the stock forks. I most certainly will keep this great forum posted on my progress, but am just drafting out my plan for now. It involves grafting in some modern cartridge forks to the stock BSA hub. This likely will be my first attempt at making custom yokes.

Would any of you know the OD (outside diameter) of the steering head bearings outer race that fits into the frame. I am trying to source a good set of tapered bearings, but did not want to take the whole fork apart on my bike during this planning stage (If I can avoid it).

I found a measurement of 1.78386" (45.31mm) doing an internet search, but this may just be for an oil in frame set up (part number 97-4031).

I think that the stock part number for my steering head bearings is 99-9913 and just the outer race is 66-4149.

Thanks in advance.

Image

blaise
>180
>180
Posts: 187
Joined: Thu Dec 13, 2012 10:22 pm
Location: San Carlos, CA. USA
Flag: United States of America

Re: Fork mods

Postby blaise » Wed Feb 05, 2014 1:28 am

Oh, I just got some information on this, with a measurement of 2.125" (2-1/8").

User avatar
HPbyStan
>1400
>1400
Posts: 2873
Joined: Mon May 24, 2004 9:31 pm
Location: Janesville, Wi. USA
Flag: United States of America
Contact:

Re: Fork mods

Postby HPbyStan » Wed Feb 05, 2014 1:42 am

I just today turned out two adapters to mate TT500 Y*maha taper bearings to the '67 C25 frame I'm putting the '71 B50 engine in for my NZ mate to ride in the int BSAOC rally in Petaluma in May. I made the steering stem from Aluminum bar stock to fit Ceriani clamps although I made my own clamps as well.

blaise
>180
>180
Posts: 187
Joined: Thu Dec 13, 2012 10:22 pm
Location: San Carlos, CA. USA
Flag: United States of America

Re: Fork mods

Postby blaise » Thu Feb 06, 2014 8:14 pm

HPbyStan wrote:I just today turned out two adapters to mate TT500 Y*maha taper bearings to the '67 C25 frame I'm putting the '71 B50 engine in for my NZ mate to ride in the int BSAOC rally in Petaluma in May. I made the steering stem from Aluminum bar stock to fit Ceriani clamps although I made my own clamps as well.


Stan,

Hopefully we can meet in May in Petaluma. I plan to be there.

Blaise

gpvictor
>20
>20
Posts: 32
Joined: Sat Aug 30, 2008 6:30 am
Location: Bristol
Flag: Great Britain
Contact:

Re: Fork mods

Postby gpvictor » Thu Feb 06, 2014 8:30 pm

Hello Stan,
I am pushing my nose in un-invited but is an aluminium stem going to work ok?
Co-efficient of expansion of a steel headstock and an ally stem and all that implies. You could use a bit of 1/2 inch steel rod with ally inserts to pack out to the bearings if you haven't got a piece of inch steel tube - you only have to clamp the bearings in the headstock - the stem doesn't take a lot of force.
Sorry, if you have discarded this idea already.
Mike

blaise
>180
>180
Posts: 187
Joined: Thu Dec 13, 2012 10:22 pm
Location: San Carlos, CA. USA
Flag: United States of America

Re: Fork mods

Postby blaise » Mon Feb 10, 2014 8:31 pm

Here is my first lower yoke design drawing. It is basically inspired by the stock yoke, but meant to grasp a larger fork tube (1.690").

Image

This is my first time making a yoke, so am wondering if anyone has tips on making the steering stem.

How is it typically secured to the yoke? This yoke will be made of 6061 aluminum. I think that on my BMW, it is simply pressed in (actually expand aluminum to slip steel stem in).

fastharry
>120
>120
Posts: 123
Joined: Tue Dec 14, 2010 9:40 am
Location: Leicester England
Flag: England

Re: Fork mods

Postby fastharry » Thu Mar 06, 2014 6:56 pm

I have several spondon engineering steering sets, they are all alloy and the stem has a small top hat at the bottom to stop it pulling through the bottom yolk, it is just pressed in,

blaise
>180
>180
Posts: 187
Joined: Thu Dec 13, 2012 10:22 pm
Location: San Carlos, CA. USA
Flag: United States of America

Re: Fork mods

Postby blaise » Thu Mar 06, 2014 7:43 pm

fastharry wrote:I have several spondon engineering steering sets, they are all alloy and the stem has a small top hat at the bottom to stop it pulling through the bottom yolk, it is just pressed in,


Thanks


Return to “Tech”

Who is online

Users browsing this forum: Bing [Bot] and 6 guests