Fork Oil Change Made Easier

[hppants]

To clarify, on my Gen 1, I put an exact volume of oil in each fork. I believe it was 655 cc. I have a graduated funnel that is pretty accurate (to within 5 cc). I always did that with the forks extended. I must be mistaken regarding the oil overflowing issue, I've done this on a lot of motorcycles and some of them are this way (overflowing when fully compressed).

Regarding the Gen III oil levels, can anyone offer the exact volume for each fork, perhaps from the field service manual, as opposed to adding oil up to a certain level?

 

[gixxerjasen]

Aha. There's a difference between putting a measured amount into the forks and filling up to a "Full below the top" method. The method used by the original poster is the "Full below the top" method where you have the fork compressed and fill to a specified distance from the top of the tube. Both will work, it just depends on what tools you have on hand. Obviously your garage is blessed with nice measuring devices.

 

[MCRIDER007]

To clarify, on my Gen 1, I put an exact volume of oil in each fork. I believe it was 655 cc. I have a graduated funnel that is pretty accurate (to within 5 cc). I always did that with the forks extended. I must be mistaken regarding the oil overflowing issue, I've done this on a lot of motorcycles and some of them are this way (overflowing when fully compressed).
Regarding the Gen III oil levels, can anyone offer the exact volume for each fork, perhaps from the field service manual, as opposed to adding oil up to a certain level?

The problem with filling the forks by volume is that you will never get all the old oil out unless you completely disassemble the forks so your oil height usually will be be less than recommended but to answer your oil volume question, the stated oil volume in the 13A service manual (14A is probably the same) is:

716 cc (24.21 US oz) on the left fork, 694cc (23.46 US oz) on the right fork.....which seems to be backwards from the recommemded 106mm oil level on the left fork and 90mm oil level on the right fork....but probably is correct if the right cartridge has damping pistons and the left cartridge does not.

 

[hppants]

I think technically - the "Fill below the top" method must be more accurate. I suppose sarcastically, "drip dry" for each fork still leaves a film of 1.7 cc (give or take 0.8cc) of fork oil in the fork. One could also assume that in the absence of disassembly, some grunge is left in the bottom of the fork leg, which of course takes up some volume in the assembly, and can throw the overall expected volume of oil off. Again - a miniscule amount, IMO.

Since the spec is EXACTLY 716 cc/649cc, it would appear that Yamaha feels pretty passionate about the volume of oil in the fork. I've changed the fork oil/seals in 10-15 different motorcycles - that doesn't make me an expert. I've noted the S/M volumes in my owners manual (where I have all kinds of tidbits I've picked up in preparation for doing the maintenance on my bike). I'll probably go with my volume method and then take a measurement and see where it falls. Since I'm lucky enough to find good balance in having the dampening settings in the middle of the range, I suppose I could always adjust the suspension to compensate for any minute differences the oil volume may displace. But truthfully, I don't think I will be able to notice it.

Good discussion for me - I'm more of a parts changer than a mechanic. It helps me to understand the science behind the maintenance. I can then decide how far I need to take it, and still feel comfortable about what I'm doing,

 

[rbentnail]

Want a better way to service your forks?
Call dealer, make appointment. Drop off bike. Go do whatever you want to do. Get phone call, go pick up serviced bike. Pay nice people for doing that bullshit for you. Ride away happy.

You can thank me later.

Until you find the dealer broke and/or fucked up stuff on your bike. Never again. I'll suffer through trying to learn to do something myself, em-bare-ass-mint included.

 

[MCRIDER007]

Since I'm lucky enough to find good balance in having the dampening settings in the middle of the range, I suppose I could always adjust the suspension to compensate for any minute differences the oil volume may displace. But truthfully, I don't think I will be able to notice it.

Oil level is not going to change damping unless the level is so low that it is below the top of the cartridge. It only changes the way the forks respond at the end of the compression stroke under heavy braking... too little oil and the forks may bottom too quickly, too much oil can reduce the total amount of travel available before the forks bottom.

 

[hppants]

That makes good sense ^^^^. As long as there is a head of oil on top of the dampening orifice(s), then dampening will occur.

Also, couldn't the "dead fork" actually have a cartridge in it with a fixed orifice in the "piston" (or whatever it is called), and not have the adjustability?

I guess I've jacked up this thread pretty good. Apologies to the O/P.

 

[MCRIDER007]

Also, couldn't the "dead fork" actually have a cartridge in it with a fixed orifice in the "piston" (or whatever it is called), and not have the adjustability?

That is what I would expect but according to Motorcyclist, Traxxion, and GP Suspension it is not the case. See Post #37 in this thread.

 

[want2ride]

I just changed out the oil in my forks. Reading Pants write up on this was a big help. It was a nasty black oil that came out of the forks. Since the bike is new to me I have no idea how old the oil was. I used a entire quart of ATF to flush them. Tomorrow I shall take it for a test spin and see how she does. This spring I will swap out the springs and change the valves as suggested to improve the handling. Yes the rear shock should also be changed....

Thank you all for the enlightening information you share here.

By the way, I have put 11K on my FJR since getting it the end of February. 11k of fun filled miles!

 

[painman]

Thanks to this great forum I have learned and performed many maintainence items that I would have never attempted on my own over the years. And thus have the personal satisfaction of knowing it was done right even if it was difficult to do at times. And not to mention the hundreds of dollars saved in the process. This place rocks! PM.

 

[Lowcountry Joe]

You will be ahead of the game if you always take a measurement of the height of the oil in each leg BEFORE you start tearing down. You will NEVER get all of the old oil out unless you totally dismantle the leg and wipe/clean surfaces of EVERYTHING that is in the leg and the interior walls of the legs themselves.

So there's really no need to be so anal about this procedure. Proper height of the oil in each leg trumps quantity of oil every time. If you stick to a quantity fill, then you may be screwing-up (the required air space) unless you take it all apart and clean absolutely every surfance of everything in the leg....and why do that for a simple fork oil change?? Even then, oil height still trumps quantity every time...every time. The air space is all important.

There is no way I would ever allow this (or much of anything else) to be done by a dealer. It's way too important to do it right.

 

[Fred W]

I agree that measuring the air space is (by far) the preferred method. I really don't really see the point of trying to measure when what you are trying to do is create a specific air space, and it is easy to measure when you are filling. They also have these handy syringes, for the truly anal among us, where you slightly overfill the leg, set the air space height on the syringe's needle and then suck out fluid down to the exact level you want.

That seem like a cool way to do it, though I've always just used the old school method of a little 6" metal scale and iteratively filled to the desired level.

All of that said, the fork air space is just another parameter that you can use to tweak the suspension's performance characteristics. Not many folks obsess over reproducing the exact viscosity of their stock fork oil, and will often use something other than the OE oil to attempt to change the overall damping.

That air space above the oil will influence the "total" spring rate, adding more or less "progressiveness" to the fork springs. As long as you do not put so little oil in that the dampers suck in air, or put so much that you get hydraulic lock and blow out the seals at full compression, you can play with that level to your heart's content.

 

[Lowcountry Joe]

I use one of those MP syringes and it comes in handy for sure. Kudos to the OP for making his own...but I like storebought for some things.

 

[gixxerjasen]

They also have these handy syringes, for the truly anal among us

Speak for yourself. They also are easy and work really well for the lazy among us.

Fill it, set it, suck it, done.

Ok, that didn't come out quite right...

 

[Fred W]

Being anal about service tasks is not necessarily a bad idea.

 

[Lowcountry Joe]

 

[HaulinAshe]

By far the MOST important thing is to change the fork oil periodically. The interval truly depends on three major factors; mileage, time and typical riding conditions. Just like engine oil, if fork oil has degraded to a point where it has lost its viscosity and lubrication properties, you've probably screwed up the internals. But long before that happens it's the contaminants in the fluid that truly wreak havoc.

If you have a fork oil tool, great! Love the homemade tool shown earlier, classy! I eventually bought a MP version after a few thousand fork oil changes with my old homemade turkey baster tool.

If you don't have a fork oil tool use a cheap metal scale or similar to slowly add and measure to the proper level. 5mm either way is almost impossible to detect in performance. Especially since as stated earlier, it really only matters when the fork is nearing full compression. You're usually too busy with other concerns to say to yourself... "Hmmmm, that right fork feels like it may hit the deer a little harder than the left fork."

If you live in the dreaded north (I'm sorry, did I say that out loud?) and only ride your FJR a few times each year, you can probably do fine changing fork oil ever other year. If you frequently pursue goat paths, banjo music and frequently wipe rain, mud or frost off your face shield, you better change that dead-cat smelling stinky fork oil at least annually.

Remember it's the impurities/contaminants that matter most, not how exacting you are with the oil level. Follow the manual. Get it close. Do it often enough.

 

[Niehart]

^^^^^^^

Like

 

[LKLD]

Want a better way to service your forks? Call dealer, make appointment. Drop off bike. Go do whatever you want to do. Get phone call, go pick up serviced bike. Pay nice people for doing that bullshit for you. Ride away happy.

You can thank me later.

Thought I would check into the dealer, being as I'll be getting a rear tire put on before going on a trip next month. Quote was $250, plus parts...............for EACH fork! F%#k me! I'll definitely be doing it myself.

 

[HotRodZilla]

Want a better way to service your forks? Call dealer, make appointment. Drop off bike. Go do whatever you want to do. Get phone call, go pick up serviced bike. Pay nice people for doing that bullshit for you. Ride away happy.

You can thank me later.

Thought I would check into the dealer, being as I'll be getting a rear tire put on before going on a trip next month. Quote was $250, plus parts...............for EACH fork! F%#k me! I'll definitely be doing it myself.

Holy crap. I was with you until you said EACH. Jeeze, my dealer is around $250 for the full job. No wonder some of you hate your dealers so much.