Suspension help please!

[klx kid]

here goes

i brought my 2007 YZ125 second hand off trade me in about march this year. when i brought it i had do replace the front fork seals but i did not do anything to the rear suspenion. as i have raced my bike over the last few months i have noticed that the back is starting to sag alot lower than all my friends yz's and also lower than when i first got the bike (it has gone down approx 4cm) it is also getting very soft. i have put the suspension higher and tried to make it stiffer but it just sags under its own weight to a certian point (this is always the same spot it sits at no matter how much i change the settings).

does anyone know what this could be????? its getting worse as i ride and getting lower by about .5-1cm each 2 racedays (once a month)

[CRF119]

Make sure all of your linkages are working with no binding.

Do you have a stand that your bike sits on when being stored so both wheels are off the ground?

Maybe get the spring cheeked they can start to sag over time but its a new bike i wouldnt think it would do it so soon. My mates quad got lower and lower over time to. Must be a yami thing

[little.whittle]

Must be a yami thing[/QUOTE]

They also tend to need fork seals replaced often:doh:

[evoetr]

I'm guessing that it is height adjustable where the spring sits ? If so read below

At the top of the rear spring (What the spring sits hard against will be a plate that can screw up and screw down.... Normally there are two plates to stop them un-doing when riding. You probably want to check that you can't turn that top spring plate with your hand or if the thread is chipped or cross threaded etc.

Just an idea, think its bit more serious then that though.

[K6K]

the static sag is distance between the axle and guard with the wheel unloaded and on the ground with no rider weight. I think it should be 35mm or so (check your manual). The static sag is adjusted by preload on the spring. The more you screw down the spring the less the static sag there will be (tighter spring will compress less under the bike weight).
You may get the static sag right but have the wrong riding sag (should be 100mm or so - check your manual) In which case you may have to change spring rates.

How are you making the bike higher?

[klx kid]

the static sag is distance between the axle and guard with the wheel unloaded and on the ground with no rider weight. I think it should be 35mm or so (check your manual). The static sag is adjusted by preload on the spring. The more you screw down the spring the less the static sag there will be (tighter spring will compress less under the bike weight).
You may get the static sag right but have the wrong riding sag (should be 100mm or so - check your manual) In which case you may have to change spring rates.

How are you making the bike higher?

i have been raising the bolt that is around the spring. therefore making the spring higher......u might be on to something with my sag ect....?

[K6K]

raising it up will make the spring softer therefor giving you more sag! Try the other way...
Take care to set your riding sag also... you can adjust the preload a little bit to get the right riding sag but as I said you may need to change the spring.

[klx kid]

Make sure all of your linkages are working with no binding.

Do you have a stand that your bike sits on when being stored so both wheels are off the ground?

Maybe get the spring cheeked they can start to sag over time but its a new bike i wouldnt think it would do it so soon. My mates quad got lower and lower over time to. Must be a yami thing

there is no binding...... and my wheel is always off the ground when i store it.

[klx kid]

im only bout 60kg so i dont think i need to change the spring. il try settin it nw

[little.whittle]

im only bout 60kg so i dont think i need to change the spring. il try settin it nw


Use these as guidelines to set up

http://www.motocross-racing-tips.com/dirt_bike_suspension.html

[K6K]

im only bout 60kg so i dont think i need to change the spring. il try settin it nw

60 kg maybe a bit light for the spring. the manual will say what the standard spring weight is, what color the marking is on the bottom of the spring and what weight range it is for. If you are a bit light you will need to back the spring right off (winding up) to get your race sag which will screw up the static sag.

[klx kid]

thanks for the help every1. steve helped me fix it all. (everything was in funny places and all out from previous owner)

[Robert Taylor]

thanks for the help every1. steve helped me fix it all. (everything was in funny places and all out from previous owner)

How many hours has it done on the shock without a rebuild? Every single lap on a typical motocross track is equivalent to approximately 17,000 compression cycles. Ordinarily the shock should be serviced at least every 20 hours for peak performance, and thats just not a simplistic view of just ''reoil and regas'' !!!!

Aside from worn and seizing up linkage bearings mentioned by others the piston ring band and energizer rings inside the shock could well be appreciably worn if the shock has done a lot of hours, the oil could also be quite emulsified due to nitrogen migration.

Worn piston ring bands creates unwanted oil bypass and it can measurably affect static sag as there is less positive pressure on the compression side of the piston.

The stock spring ( if it is still stock ) is too firm in rate for you. When you set it up for a ''correct'' rider sag figure of around 100 to 105mm there will end up being too much resultant free sag because you havent had to preload the spring too much.

In simplistic terms a 2 to 3 year old MX bike is roughly equivalent to a 10 year old car, wear wise. A car being driven on a mx track over the same period would have major wear issues as its a very demanding environment that is very hard on equipment.