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Before the warm weather gets here I would like put some new oil in my forks. I already spoke with Rod from RMR Suspensions about how much oil and what weight to use, but I am wondering what the process is like? From what I read in the manual, when I undo the top caps, the damper rod will come out as well, then I can just pour out the old fork oil. I will put some new oil in, compress the fork to flush it around and then drain that. I know the amount to put back in is 110mm from the top, fully compressed, no spring. But what settings will I lose from doing this? Rod said my bike was set up really well and not to change anything. Will I lose any rebound or even preload settings? If not the preload is easy enough to see where its at. I would like to make sure that my setup is the same after doing this.
 

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Some forks have a drain screw down near the base. But be sure that it IS a drain screw and not the compression damping adjuster. But to drain them you need to pump them through a few strokes so you need to support the front of the bike and it's also a lot easier to remove the front wheel and fender so you can do one side at a time. A ratcheting tie down strap can be used to lift the front up if you have a skyhook or rafter handy. If there's no drain screw then you pretty much need to remove the leg and tip it out.

If the stuff that comes out is really iccky looking (THAT'S A TECHNICAL TERM!! :D ) Then it would be a nice idea to sacrifice some of the new oil to fill, flush with a bunch of strokes and drain before filling with the good stuff a second time. I've seen some scarey stuff come out of some fork legs and I've seen stuff that I'd be happy to use over if I was cheap. You never know until you drain it.
 

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how about the seals?
Do they just pop off, or is there a technique, or special tool involved?

heh looks like I'm not the only one feverishly trying to prep a heap of junk before the spring kicks in full swing :)
 

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I'm surprised no has added carefully! :)
 

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The degree of difficulty depends on what type of fork you have. Old-style damper rod forks or air forks are often just drainable through a screw or pour out if removed. Make sure if you drain them that you look real closely at the drain screw as you remove it from a loaded front end.

A cartridge fork cannot be serviced this way. You'll never get all the old crap out. What I do is remove the legs, pour out what I can, after taking springs and spacers out of course, and then pump what I can out by flushing with kerosene and vigourously working the action to get all the crap out. I then hang them upside down over a bucket for a day or so, working the action occasionally, to make sure I have everything out.

CR
 

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TeeTee said:
Some forks have a drain screw down near the base. But be sure that it IS a drain screw and not the compression damping adjuster. But to drain them you need to pump them through a few strokes so you need to support the front of the bike and it's also a lot easier to remove the front wheel and fender so you can do one side at a time. A ratcheting tie down strap can be used to lift the front up if you have a skyhook or rafter handy. If there's no drain screw then you pretty much need to remove the leg and tip it out.

If the stuff that comes out is really iccky looking (THAT'S A TECHNICAL TERM!! :D ) Then it would be a nice idea to sacrifice some of the new oil to fill, flush with a bunch of strokes and drain before filling with the good stuff a second time. I've seen some scarey stuff come out of some fork legs and I've seen stuff that I'd be happy to use over if I was cheap. You never know until you drain it.
If the oil is drained through the drain hole, Does the top cap still need to be removed to fill with new oil? There isn't a fill hole is there? Sorry, new to bike servicing.
 

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lilfizzer said:
If the oil is drained through the drain hole, Does the top cap still need to be removed to fill with new oil? There isn't a fill hole is there? Sorry, new to bike servicing.
Even when there is a drain screw at the bottom of the fork they should be taken apart and cleaned propper. The grey sludge at trhe bottom is alum. wear and broken down oil. As the oil breaks down it starts to wear into the sliding parts of the forks. The problem is that if you were to have a set of wore or very used forks and a set that was changed regularly you wou absolutly feel the difference. You just don't feel it because they were slowly. Fork oil should be changed on a street bike at least every 20,000 kms or if you are a rider that pushes a bike then sooner. If you are on a track it should be changed at least every four weekends. On bikes that are raked out they need to be inspected on a regular bases because the bushing have a tremendous amount of pressure on them and wear sooner. ie Virago's.
As far as changing the oil, damper rod forks are very basic to change but still have to be taken apart because they wear the most. On cartridge type forks they have to be set up propper to get the most out of a stock fork. Please use someone with experience in good bike set up. There are things in the chassis set up that makes a bike handle way better then when they come out of a create. Remember "The best You Know Is The Best You've Riden" not my quote but very acurate. So if you have not riden a propperly set up bike then you don't know if yours can be better. Back to the cartridge oil change I will say that most dealers when doing the oil change or oil fork seal change NEVER ask if the bike is diving, bottoming, falls into a corner, hard to turn in, pushing under acceleration, bad tire wear, and more. These are all things that can be helped at that time of the work. So yes changing the oil is very important and putting them back together even more important, if you want the best handling chassis you can. I mean you don't have to be a speed freak to want it to handle good with out having to say well it's just me that is they way I ride or that is how that bike handles.
The shock is another item that needs attention. You change your engine oil every 3,000 kms because it will wear or your motor. Well the forks and shock are the same. Also the nitrogen looses pressure every year. Needs to be checked.
Who ever you take your bike to ask more questions about how to get your bike handling better and there are things that don't cost in order to make your bike better.
 

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I agree with RMR. It's always best to do it right. I think the drain screw is more a convieneince for folks that drain it more often or are switching viscosities more often so they don't actually need to disassemble the whole front end. But it really makes it harder to do well if you use the shortcut.

Lilfizer, you can't just fill it through the top with the cap on even if there was a "fill screw" which there isn't. All the manuals I've ever seen provide two measurements. One is an approximate volume of oil to use and the other is a measurement in inches or millimeters that the oil should be from the top rim of the tube. It is this top rim to oil measurement that is the critical spec. The volume is only approximate.

To measure that distance you need to take off the cap and lift out the spring and any spacers (spacers are always at the top anyway) and force the fork to compress totally and only then do you add the oil and adjust to get the right top rim to oil level measurement. Be sure to back out any preload adjusters before unscrewing the cap.

By now I think most of you would agree that the draining, flushing and refilling plus measuring is going to be a whole ton easier if you take the time to do it right and pull the whole fork leg out of the bike.

BTW, if the oil is reallllllly messy and it needs a good flushing out then you can use a two stage flush that'll really clean it super well. First drain the old stuff with some pumping strokes until you only hear air moving around. Then add about 500 ml of solvent and pump up and down about 3 dozen times to flush the solvent through the whole system. Tip and drain out the grunge with more pumping until you hear only air moving again. Repeat with solvent if it's still black and particles run out at the end of the first flush drain. Now fill with 500 ml of automatic transmission fluid and pump another 2 or 3 dozen times to flush with the ATF. Drain well with more pumping strokes to pump the oil out of the circuit as before. Let stand upside down for a couple of hours to drain well. Finally now you can stand it up and collapse the fork leg and fill with the proper oil of choice until it reaches the measurement listed in the service manual. This varies from bike to bike but for smaller bikes 4.5 to 5 inches is fine or until the top of the inside damping cylinder top that you can onlyl see with a flashlight is covered by about one inch of oil if there's any doubt. Pump the leg a few times until you don't hear any air moving around other than perhaps the odd "squish pop" here and there. Recheck and adjust the oil level with the leg compressed. That's done.

If the old oil came out nice and clean you don't really need to do all this flushing stuff. As said before I've seen prime examples of both extremes. If it's sort of inbetween then I'd suggest the ATF flush and skip the solvent steps. The solvent is really only for extreme grunge cases.

Extend the leg, insert the spring and any spacers and replace the top cap. Be sure to keep a firm and steady pressure on the cap until the first 4 or 5 turns are engaged to prevent the threads ripping out. The preload aduster should have been backed out first before you took it apart so once the top cap is back on it's time to reset it so it's where it started at.
 

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I just re-read Rod's post above this one. There's some fantastic gems in there. Good on ya for sharing Rod!

So many of you out there don't know just how good your bike can be made to feel with just a few tweaks of the suspension but yet you'll think nothing of spending a ton o' bucks on a noisy exhaust or the latest graphic hero helmet. Do yourself a favour and get your suspension tuned. Unless you're super lucky to have gotten a bike that just happens to have been set to match your weight I can guarantee that you'll be shocked at how much better the bike feels after even a few basic setup adjustments. It's my experience that only about 5% of the bikes out there are set properly. The others all need adjustments and/or component upgrades to be setup properley.
 

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People doing there own oil change should be checking the bushings at the same time. If there is 20,000 kms on the forks or the oil is very dirty then the bushing really need to be check. Remember if the oil is broken down then the wearable items such as the bushings could be worn through the teflon. Coventional or upside down. In a cartridge fork the teflon band on the rebound piston and or the seal between the damper rod and cartridge needs to seal propper or you will have blow by. This means the oil is not going though the valving causing the cartridge to be not working the way it should. The last thing is setting the cap (rebound) and preload correctly. There is also a correct amount of preload against the spring for the fork to work correctly. To much preload with an under rated spring and you get not enough free sag. This is usuall with sport bikes. The forks have too light a fork spring and too heavy rear shock spring. This is why getting your bike set up correctly will help you ride safer and make biking way more injoyable.

We offer bike set ups for $40.00. This gives you the best set up that the stock suspension can offer. We adjust the preload to set the chassis front and rear and then adjust the clickers. It makes a difference!
 

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If you don't know how to change your fork oil you should consider taking it in to a shop....sometimes trying to save a few bucks is not worth putting yourself in danger....just spilling oil on your brakes is one of the many things that could go wrong....if you don't put the right amount in or change the dampening settings you could get speed wobbles or excesive diving during hard braking...if you disassemble the front end and don't put it together propper things can fall off or worse...jam up the front wheel and make you fall.....the "tuning" of the forks dictates how the bike will steer into and through the corners.....some things are best left to pros....a good suspension shop/guy can make your bike ride and turn better than you can imagine....an experienced rider/racer can feel 2 clicks change in the front...
 

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make sure if you are doing the quick oil change method (20 min a side) where you drain and fill without taking the damper rod out, that you pour the old oil into a container and mark it, then clean it, and fill the clean container with the new oil TO THE SAME LEVEL, that way, you only put back in what you take out! Because these "quick changes" only drain like 90-95% of all the oil. And because they are "quick, it means you are not taking all the shit off the top so you will not be able to measure the level and you wanna make sure you keep it at the right level (assuming there are no leaks) If it's leaking take it in....
 
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