Commando 850 Forks very stiff damping.

Joined
May 16, 2021
Messages
24
Country flag
Hi. I have just purchased an 850 1974 Commando and the front forks are very stiff, almost no damping at all. The front wheel is skipping over the bumps and its not a pleasant ride. Does anyone have any ideas please??
The seals are fine and no leaks but I have not checked anything yet. Could it be to much oil or not enough or wrong oil or is it more likely something else. I have a 750 Commando to compare them with so I know they are very stiff.
Thx for any advice!
 

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
17,771
Country flag
The title is "very stiff damping" but then you say the "forks are very stiff, almost no damping" so which is it exactly?

I have not checked anything yet. Could it be to much oil...

Possibly (reduction of fork movement?), if significantly overfilled.

or not enough

I'm not aware of not enough oil causing too much damping so that is unlikely in my opinion unless the forks are almost bone dry that might cause the stiffness.

or wrong oil

Yes, it could be.

or is it more likely something else.

It could be something else but due to the lack of information, I couldn't say if it is more likely or not.

Thx for any advice!

I suggest the first thing would be to check the fork alignment and change the fork oil.

If that doesn't cure the problem then time to strip the forks and investigate further.
 

holtcorseaux

VIP MEMBER
Joined
Jan 18, 2016
Messages
149
Country flag
Hi. I have just purchased an 850 1974 Commando and the front forks are very stiff, almost no damping at all. The front wheel is skipping over the bumps and its not a pleasant ride. Does anyone have any ideas please??
The seals are fine and no leaks but I have not checked anything yet. Could it be to much oil or not enough or wrong oil or is it more likely something else. I have a 750 Commando to compare them with so I know they are very stiff.
Thx for any advice!
Hi could it be springs too stiff? For example, progressive springs are too stiff in my limited experience. Nothing to do with damping.

Have a good weekend

Martin
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
17,404
Country flag
As LAB has said, being very stiff and having no damping are really two different things.

Someone could have put over stiff springs in. Stanchions could be bent. Bushes could be tight. Could be bunged up with rust. Etc.

The only way too much oil could cause what you suggest is if they’re so full they’re hydraulically locking. That’s the easiest thing to test… just drain the oil.

If that doesn’t work, which I kinda doubt, gotta strip ‘em and have a look.

They’re simple to work on which is good, but it can also be bad as it can lead to unsympathetic mechanics throwing them together without care, causing them them to stick and bind etc.
 
Last edited:
  • Like
Reactions: baz

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
17,771
Country flag
Also, check both yokes are the correct ANG-marked 850 items as a mismatched pair (one ANG and one 750) would twist the fork legs out of alignment.

Commando 850 Forks very stiff damping.
 

baz

VIP MEMBER
Joined
May 26, 2010
Messages
4,444
Country flag
You could check the oil first as a minimum
These bikes are only as good as the last owner
It could be many many things. Causing it
Bent leg
Pattern parts or simply poor assembly could cause this
 
Joined
Mar 14, 2021
Messages
107
@Peter Waller if the bike is new to you, I suggest you empty the oil out of the drain plugs in the sliders to start with.

You don't know how much is in there and what the viscosity is at the moment.

Leave it overnight to fully drain out, then refill it the next day.

Use proper 20 weight fork oil and fill each with 125cc instead of the 150cc detailed in the workshop manual.

Take the bike around the neighborhood and see what you think, then top up if you feel it bottoming out.


It's cheap and easy to do - only a couple of bucks for some oil, but at least you know where you are before you start thinking about tearing things down.
 

baz

VIP MEMBER
Joined
May 26, 2010
Messages
4,444
Country flag
Too many variables here
As gforce says the oil is easy to check
And If the fork weren't pumped and tightened on assembly in the correct order it could be that
What condition is the bike in ? Rebuilt ? Restored?
Best of luck with it
I'm guessing you moved on from the 750 to the 850 because you are getting older ? :D :D
 
Joined
May 16, 2021
Messages
24
Country flag
Getting older! Actually the 750 is a Norvil Race Replica and the 850 a Roadster....at the moment! Thx for the replies on the forks and will try changing the oil before anything else:)
 
  • Like
Reactions: baz

gortnipper

VIP MEMBER
Joined
Nov 11, 2013
Messages
5,360
Country flag
When you do that, and with the drain pugs out, pump the forks to expel any old fluid from the internals.

Then you can feel if there are any spots of resistance along the length of movement.

When you add new fork oil back in, you will also need to and prime the dampers. Section G8 of the shop manual describes the procedure for fork alignment and priming.
 

Tornado

VIP MEMBER
Joined
Dec 5, 2017
Messages
3,377
Country flag
The oil can fly out everywhere. Took me longer to clean the floor than refilling the fork. :) A bucket underneath and plenty of polythene next time.
Can a plastic bag be wrapped around lower end to direct spewage down into a catch can?
 

Mart UK

VIP MEMBER
Joined
Mar 11, 2021
Messages
765
Country flag
Can a plastic bag be wrapped around lower end to direct spewage down into a catch can?
Yes something like that is the way to go. Easier with the wheel out, but not easy to pump the forks then. Sure it can be done well with the wheel on and some polythene strategically taped on, to channel the oil down. I just wasn't expecting the 'splat'! Naively, I was emptying it into a measuring jug, out of interest, to see how much oil was in there. Quite a lot, as it turned out :) .
 
Joined
Jan 31, 2010
Messages
2,778
Country flag
Based on my similar experience I would drain the oil - see what comes out. If little/none or looks more like tar than oil or the opposite extreme, like dirty WD40, don't bother putting in new oil, remove the forks, strip the them down and clean/check the springs/all parts, install new seals reinstall the forks and THEN new oil.

Actually, the best practice IMO would be to just strip the forks and not even mess with worrying about what's in there now! ;) Just do it!
 

Tornado

VIP MEMBER
Joined
Dec 5, 2017
Messages
3,377
Country flag
I did the fork disassembly and new bushes/seals two seasons ago. I"m having a bit of fluid seep out the damper rod holding bolt. Can this be fixed without full tear down? I recall Ludwig stating the rod needs to be held from rotating when torquing the bolt and saying to use the drain bolt hole to fit longer bolt in to hold against the damper?
 

mdt-son

VIP MEMBER
Joined
Jan 19, 2012
Messages
1,450
Country flag
Hi. I have just purchased an 850 1974 Commando and the front forks are very stiff, almost no damping at all. The front wheel is skipping over the bumps and its not a pleasant ride. Does anyone have any ideas please??
The seals are fine and no leaks but I have not checked anything yet. Could it be to much oil or not enough or wrong oil or is it more likely something else. I have a 750 Commando to compare them with so I know they are very stiff.
Thx for any advice!
If I were you, I'd remove wheel, mudguard, springs & dampers, and check sliders for free movement. I bet one or both bind, based on what you wrote.

- Knut
 
  • Like
Reactions: baz
Joined
Jan 31, 2010
Messages
2,778
Country flag
"If I were you, I'd remove wheel, mudguard, springs & dampers, and check sliders for free movement."

I agree! FWIW, when I purchased my current Commando in '06 (from a reputable seller that stated the bike was ready to ride across the country), the front suspension, with a highly touted (by the seller) Hyde fork brace, was essentially non-existent. I discovered that one fork had no oil at all - the spring was totally rusted. The other had a few teaspoons of what might once have been oil.:rolleyes:

I stripped/cleaned everything/installed the necessary new parts and put it all back together/went for a ride. There wasn't much improvement! I disassembled again/removed the Hyde brace and the suspension transformed into a working unit. The Hyde is adjustable for fork alignment but I found that at no point in the adjustment did it allow the forks to freely move. So I tossed the Hyde in the trash can.

The point is that any misalignment of the forks will cause the problem. That can occur anywhere in the system - from the triple trees on down. Sometimes rotating the forks in the triple trees will create/remove such interference.
 

Onder

VIP MEMBER
Joined
May 11, 2010
Messages
3,355
Country flag
Let us know how it goes....and just strip it down and start over you will know what is what and it will be all correct when finished.
 
  • Like
Reactions: baz
Top