Front Fork Oil Change

[DgM]

My 1983 front forks seem to get squirrely unless road is smooth as glass, probably have original oil in them.  I'd like to drain old oil, add new oil, see if there is a difference, decide on replacing springs later.  Is it a matter of removing allen screw from top of each leg, oil drain screws, pumping forks to get ride of old oil, sealing up drain screws and adding new oil?  Anyone recommend a specific oil?  I live in SoCal so bike is usually ridden in warm/mild weather.  Thanks.

[montmil]

I'm painting parts on my VW Cabriolet right now or I'd look up the thread for you, but...  Use the Search tool as we recently went through a lengthy discussion re: fork oil. There's also a link from a guy who did a ton of research that is quite interesting. It's also a cure for insomnia. Appears that Spectro is the fork oil in official BMW jugs. Later...

Monte

[MrRiden]

The BMW fork oil at 7 1/2 weight works well in my '82 LS. I ride one up not too aggressively.  There are many other brands out there but you should know that there is no standard when it comes to rating the weight of fork oils so a BMW 7 1/2 could be the same as brand X 15 weight. Stick to one brand while experimenting. You'll need to pick up a measuring cup to replace the one you'll be taking from the kitchen cabinet for this job If I recall it takes 300cc to fill a leg but check the manual before you believe me. Whats that? Your measuring cup doesn't have marks for CC's? thats OK it will show ML and the conversion is 1cc=1ML
rich

[MrRiden]

Just saw Monte post while I wuz typin'. I have more time to kill so I think this ts the thread he referred to, hadn't read it before myself.
http://suraklyn.com/yabb/YaBB.pl?num=1216474556
rich

[nothing]

front forks seem to get squirrely unless road is smooth as glass

Also be sure to do this, quoted from Snowbum:

"When you reassemble a wheel to the motorcycle, do not forget to tighten the axle nut, and THEN bounce the fork, or rear end, before tightening the  pinch bolt(s), to help centralize the wheel in the forks or swing arms.  Failure to do this may cause stiction in the front forks, especially annoying over small road irregularities; and some rather expensive repairs to the rear drive.  Having the axle lightly greased not only protects and lubricates the fitment, but ensures the forks/arms move as required during the bouncing. "

This made a BIG difference in the straight-line handling of my bike.

[montmil]

Just saw Monte post while I wuz typin'. I have more time to kill so I think this ts the thread he referred to, hadn't read it before myself.
http://suraklyn.com/yabb/YaBB.pl?num=1216474556 rich

That be the one. Thanks, Rich!  And you ought to see the Cabrio's fender flares... sparkling. Will get 'em mounted up this afternoon.

[DgM]

Thanks for the oil info.  Question remains - can I change oil while wheel and forks are assembled on bike?

[montmil]

Thanks for the oil info.  Question remains - can I change oil while wheel and forks are assembled on bike?

Sure! Use caution when reinstalling the small drain plug bolts. If possible, use a new crush washer and DO NOT torque to the manual's specifications! Gently snug 'em up. many DIYers have regretted stripping out the threads on the fork lowers.  

To add fresh fork oil, you may want to consider a veterinarian-sized hypodermic sans needle. Easy to find and cheap. Marked in CCs. I can never hold a funnel, pour oil and keep it all in the right place.

Depending on your knowledge of the fork's service history, you may appreciate seeing the crud that is most likely living at the bottom of the fork lowers. Lots of prior posts around here on disassembling the legs. When I did the chore with my '81, I was glad to get rid of the "silt" as it most likely affected damping action. Your call.  

[DgM]

Thanks again for info - vet syringe excellent idea. I loosened, retightened axle bolts, pinch bolts, situation remains.  I'm hoping it is poor condition of oil, possible crud causing wheel chatter - it gets worse when bike has been ridden a while, fork oil warmed up.  Any thoughts on flushing forks of crud, as in riding to warm things up, draining oil, inject some WD40, bounce forks, drain, refill with new oil?

[montmil]

...Any thoughts on flushing forks of crud, as in riding to warm things up, draining oil, inject some WD40, bounce forks, drain, refill with new oil?

Way too much work!  You can pull the lower legs with a 6mm Allen wrench. Not necessary to disturb the top end of your fork assembly.

Reinstalling will likely require about fourteen inches worth of 1/4 socket extension with a 13mm on the end. It's a really simple deal and you can then be assured that all the agricultural samples are removed.

Check back in if you decided to go this way. There's a couple tips on the fork plug removal... [smiley=thumbsup.gif]

[Bob_Roller]

If you just drain the fork oil, and then put fresh oil in, the correct amount is 190 cc, if you disassemble the forks completely, 220 cc of oil.