Rare bike fork oil questions

[Zapblam]

I searched high and low all over GS and the web. I acquired an all original 1982 GN125 with 5500km last summer. Its small but it was free from a relative and I only use as a short trip work commuter. 85mpg aint to bad either. All tuned up and running perfect. The carb took some work (sat 6 years with gas) but dipped/shined very nicely.

First problem is that a manual is hard to find, year and size, you understand. Watching ebay closely.

My problem is that I do not know if there is any fork oil in the forks or how much. There is no drain plugs anywhere, and I looked everywhere. I know for certain that the oil has NEVER been changed. I cannot bottom out the forks, no oil on forks, no pits. It seems a little soft at front brake stops. Little rough on larger bumps and potholes. Its a tiny bike so I thought this was normal considering my 170lb mass.

Is there a way to check the oil level and/or change fork oil without removing the forks from the bike. Again, no drain screws of any kind. I would like to change the oil first then determine if the seals are any good. I only have 6 good months of ride time here in Canada so I am hoping I can leave the forks on bike untill fall when I park it again. I am probably SOL on avoiding fork removal.


Its not a common bike so I understand if there are no tips.

[Zapblam]

Its probably a stretch, but anyone have proper fork oil level specs for this GN125. The only suzuki shop here could not find this. Said the mechanic would probably just guestimate on a tiny bike like this.

[Billy Ricks]

Its probably a stretch, but anyone have proper fork oil level specs for this GN125. The only suzuki shop here could not find this. Said the mechanic would probably just guestimate on a tiny bike like this.

Someone here may have the spec. If there are no drains you have no choice but to slide the tubes out of the triple clamps and turn them upside down to remove the old oil. While they're off flush then with kerosene or diesel by removing the springs and pumping the fork a few times to work the solvent through the internals. Drain again and repeat a few times. You might be able to tell how high the oil should be by looking at the internal surface of the tubes.

[adamd]

Drain and add 20ml, just make sure both are even amounts.

[Zapblam]

thanks lots. I will use the 20ml amount. Probably need new seals, will soon find out.

[jimcor]

Pump out old oil

You can use a (name might be off but it's something like) Mighty Vac pump to remove oil from the forks, or one of those 12volt electric oil change pumps to suck the old oil out. Newer Concours have no drain plug (go figger) and using a Mighty Vac is standard procedure for lots of guys in COG.

[Billy Ricks]

You can use a (name might be off but it's something like) Mighty Vac pump to remove oil from the forks, or one of those 12volt electric oil change pumps to suck the old oil out. Newer Concours have no drain plug (go figger) and using a Mighty Vac is standard procedure for lots of guys in COG.

If his bike has never had an fork oil change he would do well to flush them though. Once he does a thorough job of cleaning and replacing the oil then in the future that would work great. That way he can be certain the forks are empty and after refilling he can measure where to fill to the next time.

[Zapblam]

Awsome awsome awsome guys.

I decided to remove the forks and give them a complete scrubbing. Just a tiny bit of oil dumped out. Sloshed lots of deisel to get the large amount of gunk out of them. Got as much of the gunk out as I could. I put in 20ml of 15w fork oil (spend more time with precise measuring than filling). Reinstalled the forks.

Holy moly, didnt realize how the suspension was supposed to feel. I dont have the pogostick effect anymore. (couldnt add that to symptoms as I thought it was normal)

There is a very tiny slight leak on both forks, and that I should be able to wait till fall for a seal overhall. I will keep close tabs on this though.

Thanks again for your good advise and help.

[Billy Ricks]

Awsome awsome awsome guys.

I decided to remove the forks and give them a complete scrubbing. Just a tiny bit of oil dumped out. Sloshed lots of deisel to get the large amount of gunk out of them. Got as much of the gunk out as I could. I put in 20ml of 15w fork oil (spend more time with precise measuring than filling). Reinstalled the forks.

Holy moly, didnt realize how the suspension was supposed to feel. I dont have the pogostick effect anymore. (couldnt add that to symptoms as I thought it was normal)

There is a very tiny slight leak on both forks, and that I should be able to wait till fall for a seal overhall. I will keep close tabs on this though.

Thanks again for your good advise and help.

PJ-1 makes a fork oil that has a seal swell additive to get rid of minor leaks. Yours may go away on its own. One thing you can try is to get a piece of thin rigid plastic and insert it between the seal an fork leg. Push it down and work your way around the entire diameter. It may clear out whatever is causing your leak. The leader off of film negatives is about the right thickness.