125-200cc Weight of fork oil and effects

[R-J van Hulst]

Hi
My SM 125 has non adjustable shocks.

for the street it performs acceptable yet there is one annoying element on the front fork behavior

When braking it dives simply to deep (to a extent that even with the slightest tip on the rear brake the rear wheel blocks so no effective braking in the back department)

I am not looking into a set of Ohlins I am looking for a simple remedy to improve this specific behavior.

would different weight of the fork oil be a solution and what would be a benchmark to start from and what direction to go (pretty sure that all is bone stock on this bike regarding the suspension).

Robert-Jan

 

[Dirtdame]

Heavier fork oil will slow down the stroke, but you may need to set the sag properly, or put in heavier springs, or set the oil level higher. All those things could have a bearing on what's going on with your forks. Start with making sure that the springs are the correct weight for your application. Then set the sag (1.25 inches with the bike unladen is a good general setting). Then set the oil height. Start at a stock recommended level and go up (in your case) or down 25 CCs at a time to get it correct.

 

[NCSteve]

+1 And, if the forks are stock who knows what's in there. When I serviced my stock forks there were different quantities of different looking fluid in each fork leg. Can you still adjust preload on the rear? Get your rear sag right or close before you judge your forks. Although if the front is diving in turns the springs are probably too light for your weight. Increasing oil level, weight and maybe adding some spring preload should help.
Advise is usually to make 1 change at a time until your happy.

 

[R-J van Hulst]

Thanks for the tips


attached is the fork page of the manual and the thing that baffles me is, where is the spring?

Also no spring listed in the part list.

Robert-Jan

 

[NCSteve]

That's strange. This page says you've got 40mm Zokes, if that's any help: http://www.motorcycledb.com/Husqvarna_SM125S_2011/34098

This page lists springs by dimension for referrence: http://www.racetech.com/page/title/FRSP-RT Fork Spring List

good luck!

 

[R-J van Hulst]

the motor on the page that you show is not the same as that mine is.

the engine block is an old one with a mechanical oil pump and a electrical actuated power valve.
the model I have is electrical oil pump and a mechanical power valve (same as the WR and the CR).

the picture also show a rear shock with a canister and seems to be adjustable.
mine is just a conventional spring type no adjustment at all only sag.
mine front fork is black and there is again nothing adjustable.


to come back to the issue I played a bit with the rear sag settings and stepped away from the standard setting that I have on my WR.

I set it a bit softer (sink deeper) and it improved considerably.

I think the reason is the smaller front wheel that needs the sag in the rear to be bigger to get the good balance back in this bike.

I will open up my forks in the coming weeks.

will update you if there are springs in there.

Robert-Jan

 

[R-J van Hulst]

so I played a bit more with the sag and still did get a better response from the bike

what did boggle me is that the sag setting is far far different then my WR

I dived a bit more in the details and the only explanation that I can give is this.

smaller wheel at front but also equal size of wheels.

another explanation is that the swing arm from the SM is a few cm longer then the WR.

these two bikes look the more or less the same in many aspects but there is no way that sag setting can be copied and have the same balance.

still the newer frame on the SM was even with the wrong setting noticeable better and it keeps me impressing more and more.

to be continued

Robert-Jan