Fork Oil Change Today, "Without" Fork Cap Removal

[joejeweler]

Well, today i decided to change the fork oil on my '82 GS850GL, as i've owned the bike for 6 years (it's been stored for the 3 years previous to this year).

When i bought the bike, i changed the oil, secondary gearbox, and final drive to Mobil 1 synthetic. Never got around to the fork oil,......until TODAY!

I've been using Mobil 1 engine oil for the most part when i'm running it, except this year i rode 600 miles on some Valvoline conventional motorcycle oil to do a basic engine flush due to the 3 year storage to get rid of any acid build up.

Anyway, today i decided to drain the old fork oil, and while that was happening i would take the handlebars and fork tube caps off to allow me to refill. Had it on the centerstand with some additional support at the front of the engine to take as much weight off the front tire and fork tubes as possible.

Because the oil is most likely the original 30 year old stuff, i decided to run a year with some new oil, and then next year possibly get progressives for it and do a complete teardown at that time over the winter. This would give it a season to possible have the new oil flush some additional crud out.

Well,.....i blocked off the right side rotor to avoid any oil contact, glad i did because i FORGOT i had 15 lbs of air in the forks! I had a large stainless pail to catch the old oil, but as soon as the drain screw cleared the threads the oil SHOT straight out about 3-4 FEET! OOPS!!!

.......The old fork oil was black, Black, BLACK! YuK!!

I caught the last 5 or 6 ounces in the pail,.....but the 1st 2-3 ounces i had to clean up off the tools and some magazines, and my right forearm and pant leg got a good shot!. @#$%^&*(*%#!!

The 2nd fork was no surprise and i caught it all in the pail, but i left the air in the fork as it DOES blow the crap out REAL GOOD along with the old oil! Just be ready for it.


While the fork legs were draining, i took the handlebar bolts out and bundgied it up against my Vetter fairing to allow access to the fork tube caps. I loostened the top clamps, and proceeded to "start" to loosten the fork cap.

After a turn or so, i could feel what felt like pretty good spring tension against the cap. I had visions of getting the cap off, and then a struggle to get it back on after i added the new oil!

.............and then it hit me!!! I DON"T have to take the tube caps off to refill the tubes!!!! I would do it another way......

........i'll add fork oil through the air valve! Wish i had thought of that BEFORE i unbolted the handlebars and loosened the top clamps!

Yep,.....i removed the valve cores, and rigged a 3 foot piece of clean (clear) fuel line thru the center of a long neck funnel i use to change the engine oil. I used the 1/4" ID fuel line i had used to bleed my brakes, but washed it out with tap water and used my air compressor to blow air thru it till dry, and pushed some small pieces of paper towel thru for good measure. Clean as a whistle for this job now!

The clear fuel hose was a tight fit in the long neck funnel, so i sanded the 1st 1/2" of the hose on my small drum sander (on my flexshaft tool), cleaned it up, and then fed it through the funnel until the thinned part came out the pointy part of the funnel. Once i got a grip on it, it was easy to pull the 3 feet of hose through untill just an inch of so of tubing remained in the very tip of the funnel. Plenty of tension on the tubing with no leaks. I cut off the 1/2" of the fuel line to keep it full strength where it was attaching to the air valve stem. Didn't want any slip-offs, since the pint of fork oil was "just enough" to do the job if i didn't spill any. (Haynes manual calls for 8 1/4 ounces per tube)

I used a bit heavier fork oil than the manual called for, 20 wt "PJ1" Fork Tuner Oil. (manual called for 15 wt oil) This was because i'm carrying around a Vetter Fairing with this 185 lb body. It's lmost like having 1 1/2 riders at all times. And also,....the springs ARE 30 years old!

With the low miles and no noticable bottoming out before the new oil, i was hopeful there might be a noticable improvement in the front suspension, and i was RIGHT!

Now,....what i did takes some time. The oil has to go in "while" the air in the fork comes out. I attached the fuel line to the air valve stem (core removed), and hung the funnel temporarily between some cables. Next i measured the 8 1/4 ounces of new oil in a clean plastic measuring cup, and lifted the funnel as i poured the entire oil load in.

Now you have a choice, you can hang the funnel from a line coming down off a garage beam,....or hand hold it like i did. If you have no patience, hang if from the cealing and come back in one hour or two. It works a lot like an IV bag, and you'll see air bubbles rising as oil gets into the fork and pushes out the air.

I preferred to actively manipulate the hose to keep the air bubbles coming as actively as possible. Air bubbles are your friend in this instance, for it means that oil is getting into the fork!

BUT,.....it does take awhile. It took me about an hour per fork to get each one filled. It might take TWO hours per side if you just hang the bag and aren't there to work the bubbles up and out , maybe more. But if you don't want to personally "hang around",.....hang the bag and do something else for awhile.

I actually enjoyed it,....felt like a conductor directing a symhony of air bubbles. But then i was a bench jewelry repairman for 35 years, and developed a lot of patience in that job.

Anyway, this only works "if" you have air assisted front fork caps. Without those you'll have to pull the fork caps and deal with the mainspring tension.

But if you want to do a simple fork oil change and not have to take the handlebars and caps off, this might be just the ticket!

After all the new oil was in, i replaced the valve cores and added 15 lbs of air in each fork. I've run 15 lbs of air ever since i bought the bike, and the air was still there after the 3 year storage when i got it out this year! The 20 wt oil is a BIG improvement over what was in there, for sure. The forks are much more controlled, and less jarring when you hit a small pothole or road crack. The nose dive during braking about half what it was before the change!

Next fork oil change i might try to hook up a syringe system to add the new oil, but the sharp bend thru the air valve to get into the main tube might be difficult,....although some thin hose or bending the syringe needle might work.

Frankly,.....i'm quite happy with the feel of the tubes as is,....and may never get around to progressives until these springs bite the dust. They really are quite nice now.

Low miles and center stand storage have helped the tube springs last 30 years,....but the 20 wt "PJ1" fork oil did a lot also.


PS,.....if i ever switch over to progressives,....i might pick up a spare set of tube caps for this bike. Then drill out a small hole and tap it for a screw. Regular fork oil changes would be much quicker with an access hole to allow the air to go out as the new oil went in through the valve stem.

[bwringer]

Sorry, to do it right you still have to take the fork caps off, remove the springs, and measure the level.

The volume of oil is mostly irrelevant -- the level is what's important to set correctly.

The spec requires the oil levels to be set to a specific level within 1mm of each other, and there's absolutely no way to tell what's in there now. It's very likely overfilled, since it's impossible to remove all the old oil without full disassembly.

You've certainly made a significant improvement with your shortcut, but if you go back and do it right (get rid of the added air pressure band-aid and drop in some Sonic or Progressive springs while you're at it), I bet you'll be amazed at how well these forks can work.

[tkent02]

Because the oil is most likely the original 30 year old stuff, i decided to run a year with some new oil, and then next year possibly get progressives for it and do a complete teardown at that time over the winter.

Good plan sort of. If you use ATF for a few hundred miles or so, when you do disassemble the forks to do it correctly as Brian suggests, all of the dead bug parts, mud, rust, smelly gooey stuff, and other nastiness will come out a lot easier.

[joejeweler]

Good plan sort of. If you use ATF for a few hundred miles or so, when you do disassemble the forks to do it correctly as Brian suggests, all of the dead bug parts, mud, rust, smelly gooey stuff, and other nastiness will come out a lot easier.

Sorry, to do it right you still have to take the fork caps off, remove the springs, and measure the level.

The volume of oil is mostly irrelevant -- the level is what's important to set correctly.

The spec requires the oil levels to be set to a specific level within 1mm of each other, and there's absolutely no way to tell what's in there now. It's very likely overfilled, since it's impossible to remove all the old oil without full disassembly.

You've certainly made a significant improvement with your shortcut, but if you go back and do it right (get rid of the added air pressure band-aid and drop in some Sonic or Progressive springs while you're at it), I bet you'll be amazed at how well these forks can work.

This was just a stop gap measure,.....to get the new oil helping to absorb more of the old oil residue until i dump it again,.....possibly after a few thousand miles when i next change my Mobile 1 synthetic racing engine oil out at the same time. I wanted to get a feel for the 20 wt oil also,....and with me and the extra Vetter fairing weight i do like the extra rebound control the slightly heavier fork oil gives me. At that time i may do one more flush with ATF fluid,....not sure.

I also intensionally left out 1/8 ounce of new oil,.....figuring at least that amount was left behind coating the springs and other goodies. While the fluid was draining, i did pump the forks up and down to get everything i could out, and a few extra squirts came out that way. If they are overfilled a bit,......i can't tell. They feel great, are well rebound controlled and the overall response to my liking.

Honestly these original springs feel pretty nice,.....they are FAR from being shot. The bike has low miles (14.2 K now), and i've ridden pretty conservatively over the last 4K or so i've put on. At 56 i don't take many risks. The bike accident i had when i was 16 (when we all think we're invincable!) straightened me out!!! Haven't fooled around since.....

At that time around the High School i was showing off in front of some friends (and a few girls). I popped a wheelie thru an intersection that had a huge tree blocking a stop sign,.....didn't see it in time. A car came thru at my left and his right fender smashed the left engine fins and flipped the bike 3 or 4 times. I rolled off his windshield and took out his antena, and cracked his windshield also. My Suzuki 6 speed 2-stroke 3 cylinder bike was totaled! Had it just 3 weeks and paid for it with my paper route money after saving for a full year!

I had a slight bruse on my left knee,....but at just 125 lbs (5"10" tall) i was pretty lucky. Had i been going a few MPH faster or him a little slower, my left leg would have been smashed into the bike,....likely losing it!

Anyway, i see no sense in getting progressives until these springs bite the dust. I'd rather put the money into getting the Mosfet Honda R/R upgrade, and a few other upgrades like the "harder" rear wheel spline, since mine is a 1982 model with the soft sh*t. (personally, Suzuki should have stepped up and recalled the 1982/1983 bikes and replaced the way too soft rear wheel spline )

I just installed a brand new petcock and a full set of stainless steel speed bleeders for the brakes today. In a day or two i have a front set of HEL SS braided brake lines coming. Progressives, if i get them,....will be in next years budget. A few weeks ago a new set of Bridgestone Spitfire tires went on,....had a local shop do it as at 56 i'm done hand changing motorcycle tires! A rear HEL SS brake line probably in a few weeks is next, along with a full set of EBC brake pads to see if my slight bobbing while front brake is pulled goes away. Just got thru rebuilding both front calipers, and i got the rear kit in today for install soon......

.....so much already done,......so much yet to do! I like some wrenching,......but love riding more!

[joejeweler]

Sorry, to do it right you still have to take the fork caps off, remove the springs, and measure the level.

The volume of oil is mostly irrelevant -- the level is what's important to set correctly.

The spec requires the oil levels to be set to a specific level within 1mm of each other, and there's absolutely no way to tell what's in there now. It's very likely overfilled, since it's impossible to remove all the old oil without full disassembly.

You've certainly made a significant improvement with your shortcut, but if you go back and do it right (get rid of the added air pressure band-aid and drop in some Sonic or Progressive springs while you're at it), I bet you'll be amazed at how well these forks can work.

A thought did cross my mind, and i haven't found the answer although i searched a bit on the net.

When you're setting the oil level from a cleaned out fork tube (off the bike with no spring, spacer, or washer), using factory leveling guidelines,.......aren't those levels "set" using stock springs with specific wire coil dimensions and number of coils?

Now you slap a set of progressives in, which are likely to have different total coil amounts AND wire diameter than the stock springs. The spacer used with progressives is also of different dimentions than the stock one factored in.

......so now considering these changes,.....isn't the net affect a slightly overfilled fork tube since the additional wire coil numbers, dimentions, and spacer add to the internal tube volumn? In the end, the "in use" oil level would be higher than if stock springs and spacers were maintained.

So i'm thinking all you folks wanting to totally disassemble your fork tubes to get a "precise" and accurate oil level, ......are not getting what you've worked so hard to get?

I'm a practical sort, and i cannot imagine it's all that critical as long as you don't vary drastically from a reasonable range. For sure when these bikes were new and someone went to their dealer for a fork oil fluid change,......i highly doubt the dealer is going to take the forks OUT to do the change! Yet here we are with 30 year old bikes that generally run mighty fine!

More likely the dealer would drain out what he could, measure the amount removed, and replace a similiar amount. (of course all that presumes NO oil has leaked out at the seals)

.....or as i did drain out as much as possible and work the forks several times to get more, let sit for 5 minutes, and add a bit under the factory fluid amount to allow for any risidual oil remaining. In my case i added 8 ounces in each tube where the manual stated 8.28 ounces called for. In my case draining the old oil while the tube is pressurized works pretty slick,...as my wall can testify! Pumping the forks got some more.

.....food for thought.

[mike_of_bbg]

The level measures given in the manual are fork fully collapsed, upright, no springs. Progressive springs have more widely spaced, but thicker, coils. At least mine did.

The EXACT measure of oil level is probably a bit lesser in overall importance than that both fork legs are even. What actually compresses in the forks (well, in addition to the springs of course) is the air inside of them. If the fluid levels are different than the two sides will compress at different resistance rates.

[joejeweler]

The level measures given in the manual are fork fully collapsed, upright, no springs. Progressive springs have more widely spaced, but thicker, coils. At least mine did.

The EXACT measure of oil level is probably a bit lesser in overall importance than that both fork legs are even. What actually compresses in the forks (well, in addition to the springs of course) is the air inside of them. If the fluid levels are different than the two sides will compress at different resistance rates.

You hit on the point i'm aiming at,......the "absolute" oil level is not as critical as some would make it out to be. (within reason)

I realize the oil level measures given in the manual are "fork fully collapsed, upright, no springs". But the fact remains those levels were set while taking into account the dimensions of the factory spring/spacer/washer setup.

The even fill between forks is more important i'd think, as you mention, and that can be reasonably assured by draining each fork as well as can be done while assembled. Refilling with a measured amount a bit lower than if the tubes were apart and totally dry would allow for some consideration of any risidual oil remaining in the tubes.

I plan on draining out and replacing the just replaced fork oil after 500 miles, just because i believe the oil i took out was the original. (nasty looking!) This will give the tubes a reasonable flushing.

At that time i will attempt to carefully measure the amount removed from each leg. "IF" the amount coming out is fairly even between forks, that will at least confirm some consistancy in draining proceedure. I would then keep notes on any future drain and fills, to see if the amounts removed vary significantly when compared to the previous times. The refills will be maintained at 8.0 ounces oil added per leg (for my '82 GS850GL), as that allows for .28 ounces residual oil in each tube impossible to remove from an assembled fork. (my manual calls for 8.28 ounces each tube)

I'm hoping each time i drain the fork oil over time, i get near exactly 8 ounces out!

As my forks springs have not died yet (low miles help), i'm hoping working with the bike this way will develope some useful information for those wishing to routinely change their fork oil without a total disassembly of their forks.

BTW, ...."if" the factory expected fork oil changes ONLY to be made on totally disassembled fork tubes, why did they add a drain screw at the bottom of each leg?

[TheCafeKid]

The drain plug makes a messy job less messy.

As to the point you're trying to make about different springs etc...the fork oil is to be set without any of that stuff in there... The displacement caused by different springs etc is insignificant. However, uneven loading of the axle caused by mismatched oil levels can not only be dangerous, it can be catastrophic according to some of the owners manuals...I dunno how much of that is an over blown CYA warning, but I'd rather not chance it..

[joejeweler]

The drain plug makes a messy job less messy.

As to the point you're trying to make about different springs etc...the fork oil is to be set without any of that stuff in there... The displacement caused by different springs etc is insignificant. However, uneven loading of the axle caused by mismatched oil levels can not only be dangerous, it can be catastrophic according to some of the owners manuals...I dunno how much of that is an over blown CYA warning, but I'd rather not chance it..

Not sure you can separate the two??? The displacement would seem to me to be drastically different over a stock spring setup, say, if you were to use a progressive spring in the "tight coils down" mode. Many more coils, of a thicker dimension down in the actual oil bringing the working level up.

From what i remember reading in the progressive spring install guide here, there is less fork noise than if the tighter coils are at the top. That article mentioned that progressive said it didn't matter which way the springs went in. (of course, assuming they were going in the SAME way!)

Is not the critical thing to make sure that, no matter what the fork's relative position or degree of compression, that there is oil covering the rebound control hole or holes? Anything above that wouldn't seem to be as critical, especially in a non-air pressurized fork. With air pressure run forks the oil level seems a bit more important, as the pressure rises higher with forks compressed when there is an overage of oil present. (seems that way to me anyway?)

The "CYA" warning i couldn't say for sure how critical it is to have the oil levels "absolutely" the same. With all the home mechanics, (some probably drinking a beer or two during the job? ), i'd think over the years we'd be hearing about more bike accidents caused by mismatched fork oil levels.

But certainly something to shoot for in any case!

The drain plug making it easier, ....sure. But really, "if" a fork oil change required the forks removal to to it properly, how messy is it to remove the cap and pour the oil out by tipping? Seems like the lower drain screw would be pointless if general maintainence "required" fork removal to do it properly, or was the only sensible option.

Anyone who's worked at a motorcycle dealership and are aware of their usual "MO" for changing fork oil, feel free to offer an observation....................but i'd surmise the usual course is drain from the bottom, fill at the top while assembled.

The labor rate charged to customers to do it with complete fork removal being prohibitive,......maybe that's why so many forks contain the original oil!

[1_v8_merc]

I just use the drain nut as well, then fill it up a couple ML's less than what the capacity is. If I put too much oil or air, it will usually creep out of the fork seals, then self-correct itself, lol.

[TheCafeKid]

Well, I have to say, having rebuilt many a set of forks, and being a bit of an amateur suspension set up freak, I have pretty great success doing it by the book. Not to say your way is wrong, as I've never tried it. Just seems more complicated than doing it the way I've always done it. Changing the oil is a half hour job on most models. Rebuilding the forks maybe takes an hour or two if you're being meticulous... But whatever works best for you.

[Bass Man]

GS850G newbie posting, so go easy on me! Bringing my '81 back to life, after it's been in storage since 1988. Bought it new in AZ, rode daily for a few years (18K miles), then moved across country several times, had a few kids, life happens. Then my 22 year old son says to me, " hey let's get your bike back on the road", so it's become something of a father/son bonding experience. Poured some gas in, new battery, a few quarts of Rotella 15W40 (thanks to all of the good posts on that, I used to be a firm GTX user). Poured some Mystery Oil into the cylinders. Lo and behold, the damn thing started right up! Have since rebuilt the front brake master cylinder, new front hoses. Couple of spins around the neighborhood, and it's still got that old GS magic!

Anyway, have some fork oil leakage, hoping that for now the seals will swell a bit and still hold some oil. The Suzuki shop manual has both the volumetric measure and level measure methods listed on the same page (filling while shocks apart). The Haynes manual only has the 8.48 measure. Being a manufacturing guy, I tend to think that the production line injects a given volume into each shock, assemble, and ship. Measuring the level would be cost prohibitive.

At any rate, I'm going to try a fork oil replacement with the forks on, but will risk taking off the valve cap. Will put in 8oz of oil, think that should be OK! Any recommendation on type of oil to use?

Cheers!

[tkent02]

All of the dead bugs, feces from the road, rainwater and other stuff has been in there thirty years, do it right. Take it apart, clean it out, get the oil level right.
It's very easy.

Congrats on the father / son thing, that would be great.

[Bass Man]

Road feces, hmmm, hadn't considered that...

Saw a good deal of all of that when riding in AZ. Good points, thanks man!

[Bass Man]

tkent02, I followed your guidance, pulled the shocks today, took apart, drained, cleaned, refilled (measuring cup method). You were absolutely right; it was easy (other than the end caps), and 30 years of crud in there! Used Amsoil Shock Therapy #10, seems a bit stiffer than the 30 year old gunk, but happy so far.