'Nother fork oil question:

[Rundle]

I'd like to ask people's opinions on preferred methods of achieving fork oil level. I've got new Progressive springs, new fork seals & dust caps; I ordered new fork bushings but they're on back order, and won't likely arrive before I re-do the front end.

The two methods I'm familiar with for adding the correct level of fork oil seem to be fairly straightforward: 1) add a precise predetermined amount of oil to the forks, ensuring that the same amount gets into each fork leg. Or 2) add a little more than the recommended amount to each fork leg, and remove excess oil until a precise oil level, as measured from the top of each fork leg, is reached.

My questions are; a) does one method give a 'closer to spec' result than the other? b) Progressive springs being larger than stock springs, when combined with the stock amount of oil, would it result in too much oil/spring volume and not enough air volume in the fork? I do understand that with the Prog springs, I'll likely no longer need the air-adjustment feature on my forks.

As far as amounts and measures go, I think I recall that I should be using 241ml of oil per fork leg, or an oil level 140mm down from the top of the fork. The springs are Prog 11-1107, the bike is an '81 1000GL, the apparent red-headed step-child of the GS world. (My apologies to all red-headed step-children reading this.) This model seems to be harder to find info and specs for, and I don't yet have a manual for it. I do, however, have a Chilton repair manual that covers (among many other makes and models) '77-'81 GS750 & 850. I also have the old manual from my old '83 650 Katana. (There's a great story about loss and resurrection that goes with that bike, which I'll happily tell at a later date.) These two manuals, along with blow-up diagrams from PartsPitstop.com, should be more than enough to get this done; but, not having the correct manual on hand, is it safe to assume that the forks are generally like the 1100GL, while the rest of the chassis is closer to the 1000G?

I've been searching the site for specific info and found threads dealing with similar topics, but no direct answers as of yet. Hope this isn't beating a dead horse with questions already asked and answered.

Incidentally, the bike came to me with Progressive shocks on the rear. I don't know the spring rate on them, however, the PO was about 40 lbs more than me, (I'm around 160, but gradually increasing) but rode in a much more civilized manner.

Thanks,

-chris

 

[Steve]

Of the two methods you mention, the second one is more correct. The first one only works if you know for certain exactly how much oil is in the forks to start with. The only time that is going to happen is right after you have had them apart and they are DRY. Even so, it is better to set to a level, rather than an amount.

The reason is that air is trapped above the oil. As the forks compress, the pressure of the air will rise. If the oil level is different, the pressure in the two legs will not increase at the same rate (unless you have a cross-over tube). This can lead to some interesting situations.

The Progressive springs won't occupy much (if any) more room in the oil, so they should not change the oil level when they are installed. Yes, they are thicker, but there are fewer windings.

No, you probably won't need to add any air to the forks, especially if you take the time to set the preload properly. Ideally, your suspension (front and rear) should not 'sag' more than 20-25% of available travel when you are sitting on the bike, ready to ride. Most forks have about 6" of travel, so you don't want to 'sag' any more than 1 to 1.5". Start with the preload spacer suggested by Progressive, measure your 'sag', adjust as necessary. When that is set, you should not need any additional air.

.

 

[Guest]

I marked a metal rod with the distance from the oil to the top of the forks and used it like a dipstick.

 

[dcil]

On a similar note, what fluid u guys recommend? the manual said a 50/50 mix of 10w30 motor oil and atf. Also heard type e fork oil. what is better?

 

[Guest]

I use 15wt Bel-Ray fork oil.
The mix tends to foam up.

 

[dcil]

thanks for the info. mine needs changing.

 

[Nessism]

Salty Monk's fork oil trick works well; slightly overfill the fork oil, pump the forks a few times, and then take an old spray bottle pump and use that to skim off the excess oil. Mark the dip tube for the proper height and then just pump the excess out. Works a treat to quote Dan himself (sorry, just made that last part up).

 

[82Shafty]

I added 245 cc's on a fresh rebuild per fork; per the '82 owners manual.

I used an old small engine oil container to measure out my fork oil and gave it the same amount of measured time to drain.

Also, I used 15W fork oil from Dennis Kirk this time around with much better results...the mix of ATF and 10W Fork oil sucked. Get a 15W fork oil!!!

After just 8,000 miles the mixed fluid was shot and the seals were starting to change their stiction characteristics. New OEM NOK seals and 15W fork oil made a huge difference. I had fully disassembled my forks and cleaned them thoroughly with brake clean and allowed a few days to dry out...wasn't in a hurry.

I also rebuilt the front calipers and added all SS brake lines that came in a kit for our L's. If you are interested I can send you the part number for the SS lines... I don't recall the number off of the top of my head.

 

[Rundle]

Hi all;

Thanks for your input; I've been meaning to respond, but our internet at home went belly-up a little while ago, and my opportunities for personal use of the computer here at work are few and far between, and very brief when they do occur.

I've been trying to do quick searches for confirmation on oil level for my forks, but have not found numbers that relate specifically to the '81 1000GL. Is the oil level supposed to be 140mm down from the top of the forks? As I recall that measurement is to be taken with the forks perfectly vertical, fully extended, with the springs in place; is this correct? Pour the oil in, compress the forks slowly a few times to release any trapped air bubbles, and then remove excess oil until the desired level is reached.

Also, in the absence of a proper manual specifically for the 1000GL, is the fork diagram & information for the 1100GL the same?

I know the info is here on the site, but currently I've only got computer access for 2-3 minutes at a time, a couple of times a day, so doing a full-on search is virtually impossible.

82Shatfy, if you do remember the part # for those SS brake lines, I'd love to have that info.

Thanks again folks; see you on the road.

-chris

 

[Nessism]

Fork oil is always measured with springs removed and forks fully compressed. Your 140mm level sounds about right. Remember, the main thing you are doing is adjusting the amount of trapped air there is in the fork, which will help reduce bottoming of the forks. The amount of oil has nothing to do with increasing the damping action.

 

[Mercaholic]

Fork oil mix

Fork oil mix

On a similar note, what fluid u guys recommend? the manual said a 50/50 mix of 10w30 motor oil and atf. Also heard type e fork oil. what is better?

I don't get foaming with a 50/50 mix of ATF and 10W30

 

[posplayr]

Salty Monk's fork oil trick works well; slightly overfill the fork oil, pump the forks a few times, and then take an old spray bottle pump and use that to skim off the excess oil. Mark the dip tube for the proper height and then just pump the excess out. Works a treat to quote Dan himself (sorry, just made that last part up).

Cute, I have a super size syringe I bought but this is even cheaper.

 

[Rundle]

"Fork oil is always measured with springs removed and forks fully compressed."

Thanks Nessism. Geez, I couldn't have been more wrong if I'd tried...(and the wheel with the driveshaft goes at the front, right?)

When I get my head screwed on right I'll let you know!

Thanks again,

-chris

 

[posplayr]

"Fork oil is always measured with springs removed and forks fully compressed."

Thanks Nessism. Geez, I couldn't have been more wrong if I'd tried...(and the wheel with the driveshaft goes at the front, right?)

When I get my head screwed on right I'll let you know!

Thanks again,

-chris

Most of these details are in the factory manual. If you dont have one, get one BikeCliff might have one for free download depending on your bike.

+1 on actually measuring the level v.s. trying to pour in a predetermined amount.

 

[almarconi]

Salty Monk's fork oil trick works well; slightly overfill the fork oil, pump the forks a few times, and then take an old spray bottle pump and use that to skim off the excess oil. Mark the dip tube for the proper height and then just pump the excess out.

That's the method I use, works really well.

 

[82Shafty]

GS1100GL SS Brake lines... I have them on my bike and they do work great and were easy to install.

From Bremzen Brakes

http://www.bremzen.com/store/product_info.php?cPath=345_460_619_621&products_id=20064

As you go through it, I believe it where I specified to add the rear brake line as an additional cost and to have them in black. It came to 149 plus shipping.

MSF7777-MSR7777

 

[jknappsax]

I just disassembled, cleaned out my forks out thoroughly, put in new seals, and reassembled the front end. I remember reading somewhere here that measuring the fork oil level should be done with the forks vertical, not mounted in the triples, and therefore with some rake. I just got my Progressive springs, and the instructions (which I glanced at briefly) said that since the Progressive springs take up more space, that setting by level was the correct option. I really don't want to pull the forks again, but if vertical is the best way, then that's what I should do. Opinions?

 

[JEEPRUSTY]

I may be wrong but what would be wrong with using a large syringe to measure and fill the forks?

They are accurate as that is what they are made for. That way there would be no doubts and no need to screw around.

You should be able to get a plastice one at a reasonable price at a pharmacy.

 

[BassCliff]

I just disassembled, cleaned out my forks out thoroughly, put in new seals, and reassembled the front end. I remember reading somewhere here that measuring the fork oil level should be done with the forks vertical, not mounted in the triples, and therefore with some rake. I just got my Progressive springs, and the instructions (which I glanced at briefly) said that since the Progressive springs take up more space, that setting by level was the correct option. I really don't want to pull the forks again, but if vertical is the best way, then that's what I should do. Opinions?

Hi,

I suggest you take the forks out. It's much easier to get an accurate level measurement. Have a look at these for more information.

Install Progressive Fork Springs​

Fork Seal Replacement


Thank you for your indulgence,

BassCliff

 

[1_v8_merc]

Those methods sound too complicated and anal.

I just mixed 15w30 or 40 with ATF....50-50.

Compressed forks, and added the recommended level.
Then Reassembled as necessary.


I added 7psi of air, or whatever it says.


Bike handles like a friggin dream!

Waaayyyy better than before.