A A A
Avatar

Please consider registering
Guest

Search

— Forum Scope —






— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

Register Lost password?
sp_Feed sp_PrintTopic sp_TopicIcon
D14 lightweight front forks knock on full extension
Avatar
richard hyatt
Shaftesbury, Dorset.
Forum User
Site Member
Forum Posts: 96
Member Since:
December 30, 2017
sp_UserOfflineSmall Offline
1
January 25, 2019 - 2:26 pm
sp_Permalink sp_Print

Hi all,

Occasionally , my D14 front forks give a clonk on full extension.

For example my lane has some potholes and when the forks stretch I occasionally get a clonk. 

Normal riding fine , bushes and seals and (sae20) oil fine and new , I'm assuming the damping on full stretch it what it should be.

Any thoughts please ?

Avatar
Sponge
Lancashire (somewhere near Preston)
Forum User
Club Member
Forum Posts: 113
Member Since:
November 6, 2016
sp_UserOfflineSmall Offline
2
January 25, 2019 - 5:00 pm
sp_Permalink sp_Print

Hi Richard,

Is your bike a D14/4 or a B175 model ?? this is important because the B175 forks will crash ( known fault),  if the fork slider spacers are fitted the wrong way up or left out altogether. Especially noticeable when you ride off a kerb.  Once you turn them around the problem will go away and you will have proper damping once more.  If however your bike is a D14/4 (lightweight forks) then it is possible that something in the damper mechanism is assembled incorrectly.  I am not an expert with the lightweight forks but somebody on this forum will have an insight or a solution I am sure.      

Also ........ I have found that SAE20 oil in my forks gives a very soft ride and a 'dive' when I apply the front brake.  This is very apparent on my A10 so I have changed the oil out for SAE40 on the A10 and the B175 and I now get a much nicer ride.  This might be because the average bantam rider in my youth was about 9 stones soaking wet - but I ride at 15 stones plus my riding gear and helmet etc plus whatever kit I am carrying on my bike so its not surprising that the thinner oil doesn't cope so well. 

Hope this helps

Sponge  

Avatar
richard hyatt
Shaftesbury, Dorset.
Forum User
Site Member
Forum Posts: 96
Member Since:
December 30, 2017
sp_UserOfflineSmall Offline
3
January 25, 2019 - 6:25 pm
sp_Permalink sp_Print

Hi sponge, 

Thank you for thoughts,

D14/4 as far as I know ,

When I dismantled the forks to wash them out and rebush them , I was very careful on reassembly certainly - so hopefully everything in correct order .

I've  got 1/8th pint of sae 20 as per book. The damping seems fine this weather as far as temperature and viscosity of the sae 20. But I can foresee the damping will reduce in the warmer weather for sure , so your thoughts of sae 40 sound sensible. 

Avatar
Peterg
Forum User
Site Member
Forum Posts: 1153
Member Since:
October 1, 2012
sp_UserOfflineSmall Offline
4
January 25, 2019 - 10:35 pm
sp_Permalink sp_Print

It would do. They only have one way damping, on compression. After a series of bumps the oil can transfer to the top of the forks allowing the forks to top out on the rebound. I used to get the same on the B31. BSA didn't come up with two way damping until the mid 1960's (on the heavy weights)

Avatar
richard hyatt
Shaftesbury, Dorset.
Forum User
Site Member
Forum Posts: 96
Member Since:
December 30, 2017
sp_UserOfflineSmall Offline
5
January 26, 2019 - 2:21 pm
sp_Permalink sp_Print

Thank you all,

Oil changed , see what happens , if it doesn't snow !

Forum Timezone: Europe/London

Most Users Ever Online: 98

Currently Online: swalsh58
7 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

Cornish Rooster: 3303

Anderzander: 3209

bart: 3137

Sprung Chicken: 2650

David Dale: 2491

Mags 1: 2444

Munchkin: 2218

Blue Heeler: 2145

Katj: 2139

HowD1: 1945

Newest Members:

_1620

Forum Stats:

Groups: 9

Forums: 46

Topics: 11635

Posts: 100076

 

Member Stats:

Guest Posters: 519

Members: 2859

Moderators: 2

Admins: 3

Administrators: Piquet, JMD, Rusty Floater

Moderators: cocorico, xcgb