Britbike forum

Classic British Spares Klempf British PartsBaxter Cycle BritBike Sponsor SteadfastCyclesSRM Engineering Lucas Classic Motorcycle Industrial tec supply Hepolite Pistons The Bonneville ShopLowbrow Customs

Upgrade your membership: Premium Membership
New Sponsor post
2022 Classic Triumph Motorcycle Calendars
by C.B.S - 09/28/21 6:22 pm
New FAQ post
How To: Add attached images in between text
by Morgan aka admin - 10/03/21 9:46 am
Manuals on DVD - Buy 4 for 3
All 4 DVD Manual
Member Spotlight
Roadwarrior
Roadwarrior
Nor Cal near Sutters mill.
Posts: 1,530
Joined: September 2007
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
Rohan 82
Top Likes Received (30 Days)
koan58 20
Newest Members
Pratty, AndyW, ChrisTriumph3, GLENN'S PLACE, Smartfella
11,876 Registered Users
Who's Online Now
4 members (NYBSAGUY, Hugh Jörgen, bill50cal, pushrod tom), 35 guests, and 57 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
#859668 09/30/21 1:17 am
Joined: Dec 2013
Posts: 373
C
Britbike forum member
OP Offline
Britbike forum member
C
Joined: Dec 2013
Posts: 373
Any thoughts on the amount and viscosity of oil for the M21 telescopic forks ?
BSA service sheets say 142ml of 20wt
Haynes Manual says 213ml ..
My forks are a bit 'clunky' on the rebound and in general...I had 220ml of 30wt engine oil in each leg.
More oil ? .. thicker oil ? to stop the 'clunkiness' .
Thanks friends ...Charlie.

BSA on eBay
Joined: May 2004
Posts: 4,961
Likes: 98
B
Britbike forum member
Offline
Britbike forum member
B
Joined: May 2004
Posts: 4,961
Likes: 98
M20 forks predate 2 way damping so they will always be klunky on the rebound.
There are upgrade kits to convert then to two way damped rod damper style .


Bike Beesa
Trevor
Joined: Dec 2013
Posts: 373
C
Britbike forum member
OP Offline
Britbike forum member
C
Joined: Dec 2013
Posts: 373
Thanks Trevor,can you give me details about where I can source the update kit please ??
... also,for the moment,do you have any thoughts on wt/amount of oil in each leg ? (1953 M21) .

Joined: Feb 2012
Posts: 221
P
Britbike forum member
Offline
Britbike forum member
P
Joined: Feb 2012
Posts: 221
According to BSA service sheet 706 printed in August 1963 M20 M21 M33 142cc of oil in each fork.

Joined: Aug 2001
Posts: 5,441
Likes: 57
R
Britbike forum member
Offline
Britbike forum member
R
Joined: Aug 2001
Posts: 5,441
Likes: 57
AFAIK, Paul Goff in the UK has an upgrade kit for BSA forks that contain the Dow style damper rods. There are also some drawings online somewhere that show how to make them if you have access to a lathe.

The Dow type dampers help a lot. But I had to do a lot of playing around with oils to find dampening I liked. Most oils recommended for BSA forks, are, IMO too harsh with Dow dampers. I am running 7.W shock/fork oil and the forks are really plush.


Never underestimate the human ability to elevate stupid to a whole new level!.
Joined: Aug 2001
Posts: 8,748
Likes: 89
T
Britbike forum member
Online Content
Britbike forum member
T
Joined: Aug 2001
Posts: 8,748
Likes: 89
The Dow conversion reduced the travel. Don’t know about modern versions.

If your spring length and rate and oil viscosity are right, normal road riding shouldn’t make the forks reach full extension very often.

After all, it’s the rebound movement that has damping.


Amateur Loctite enthusiast.
Charlieboy #859745 10/01/21 12:35 am
Joined: Feb 2014
Posts: 929
Likes: 140
C
Britbike forum member
Offline
Britbike forum member
C
Joined: Feb 2014
Posts: 929
Likes: 140
Hi Charlie,
If the fork legs are in good condition it is worthwhile to drill the 2 bleed holes in each one, as done on the later A,B&M models
This and the later oil quantity stops the forks topping out mechanically by trapping oil between the bushes near full extension
The top bushes need to be held tight by the circlip to stop noise, thin shims will break up in service, its better to machine off a few thou and use a thicker shim.
Adding the Dow type damper rod does not affect the travel unless you also fit the longer top bushes
I found that extra oil was needed to keep the damper valve submerged on full extension, as Rich says use fork oil and experiment with viscosity to get the effect you are happy with

John

Joined: Dec 2013
Posts: 373
C
Britbike forum member
OP Offline
Britbike forum member
C
Joined: Dec 2013
Posts: 373
Good one John,thanks for your thoughts mate .. I'll look into that.


Moderated by  Allan G, Jon W. Whitley 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5