Fork oil change mod?

[Guest]

I need to change my fork oil. I have this idea, based on past experience with other bikes:

My 78 gs1000 has air forks, which feature I never use. The air caps have a small hole going from the fitting which holds the air stem, through the aluminum caps at the top of the fork, into the fork body to allow air to pass.

Currently, one must remove the fork cap to have access to the fork tube to replace the oil. The fork lowers have a drain screw, which allows easy draining of oil.
Refilling the oil in stock configuration, means some inconvenient disassembly.

It looks possible to remove the fork caps, and from the bottom, carefully drill out the hole to a larger diameter, to allow oil to be filled from the top without needing to remove the fork cap. All that would be required would be to remove the air fitting, then refill the oil using a suitable funnel and tube, using the measured amount appropriate for the forks, in this case 240 cc.

The air fitting seal would not be disturbed, and should still work as intended. The only change is a larger diameter hole to allow oil to pass easily into the top of the fork tube throught the air fitting, either with the valve core removed, or with the whole air cap removed, whichever works best This would make the job much faster and easier.

Thoughts on this idea are welcome.

I tried to search this thread, but for some reason the search function doesn't work.

[tkent02]

You need a way to put oil up to exactly the same level on both forks. Normally done by removing the springs, comressing the fork and sucking the oil out through a tube to an exact level. The idea is not to get the same amount of oil, but to ensure the air volume above the oil is identical. This is necessary for the forks to work the best. Not sure you could do it your way.

[MAC10]

Thanks tkent,

If the forks could be completely drained with certainty, would it then work, so thst exactly the same amount of oil is in esch fork?

[salty_monk]

Within the realms of manufacturing & measuring tolerances - yes! (That's to say that perhaps the ID of your fork tubes are slightly different etc).

In practice I can't see it making much difference to you on these 35 year old tech forks!

[Agemax]

just remove the fork tops and pour the oil in. takes about 30 minutes to do both forks.......no big deal and its not like a fork oil change is a daily or weekly nessecity, once a year (or 2) maybe.

you wont notice any difference on the oil level if its a few cc's difference between legs

[oldgrumpy]

I need to change my fork oil. I have this idea, based on past experience with other bikes:

My 78 gs1000 has air forks, which feature I never use. The air caps have a small hole going from the fitting which holds the air stem, through the aluminum caps at the top of the fork, into the fork body to allow air to pass.

Currently, one must remove the fork cap to have access to the fork tube to replace the oil. The fork lowers have a drain screw, which allows easy draining of oil.
Refilling the oil in stock configuration, means some inconvenient disassembly.

It looks possible to remove the fork caps, and from the bottom, carefully drill out the hole to a larger diameter, to allow oil to be filled from the top without needing to remove the fork cap. All that would be required would be to remove the air fitting, then refill the oil using a suitable funnel and tube, using the measured amount appropriate for the forks, in this case 240 cc.

The air fitting seal would not be disturbed, and should still work as intended. The only change is a larger diameter hole to allow oil to pass easily into the top of the fork tube throught the air fitting, either with the valve core removed, or with the whole air cap removed, whichever works best This would make the job much faster and easier.

Thoughts on this idea are welcome.

I tried to search this thread, but for some reason the search function doesn't work.

....................... hi guys i used delray 10w for the forks with new progressive spring from the states regards oldgrumpy

[MAC10]

Having now accomplished this job without much hassle, I have concluded that while my proposed mod is possible, it is not that necessary. It is easy to remove just the fork tops, and refill with new oil. My fork tops removed after loosening the top fork bolt, and unscrewing them. Reinstall was a little harder, but will be easier now I have marked with a waterproof felt pen the point where the threads engage.