Bonneville America Forums Forums Technical Forums Performance Mods Bob's how to measure fork oil, forks on the bike

First off the bike must be on a lift, the kind with the two forks and a foot pump. With the bike on the lift and the front wheel off the ground remove the bars and lay them on the tank that is covered by a blanket. Remove the fork tube caps, and pull out the spacers, washer, springs of both forks. Lower the bike carefully and compress the front forks all the way up. I took it really slow because I didn't know how it would react. It wasn't a problem. At this point you could measure the oil with the T-square (see picture)and see how much was in there, or just suck it out with your mighty vac and measure the oil you took out. I did both. I noted that all the oil I could get out without taking the forks apart was 325 cc +or- 5cc. The manual says dry they hold 484cc's There is some trapped in the bottom of the leg that I couldn't get out. I measured out 325 cc's of oil and poured it into each fork leg. I then took my T-square, set at 166mm per the manual, and slid it into the leg. The wide blade of the square lets you know where the center of the fork leg is so you can get the same measurement as you would get if you held the leg straight up and down off the bike. I added or subtracted oil until both legs were the same. I shot for 166mm or a little less because the progressive springs were supposed to displace a little more oil. In the weeks to come and after hitting a few big bumps I will know if I put in too much oil when the seals blow out.. If they do I will put in a little less next time ..... Questions?

Nice illustration. Using the carpenter's square is a nice idea!! Wish mine was metric

Very cool. I'm looking forward to your next report as I'm due to change the fork oil (a little over, actually) and plan on putting in the progressives when I do.

166mm = 6 17/32nds inches +or- a dust spec on my bifocals

166(mm)/25.4(mm/in)= 6.5354' or about 6-17/32". This conversion stuff is fun.

I had to have the nifty oil level tool.
Don't remember if I got the one from Progressive or something else.
Didn't worry about volume.
Just used the tool to set the level.

Started out with one jug of Belray 10w.
Ran out & went back for another, but the place was closed.
Had to go to another shop.
They had something with a pic of a V-twin motor on the bottle.
Had to look viscosity up in a book.
They said it was 10w.
Next time I'll get two jugs of Belray for starters.

Bill
(Excelsior Springs)

Well I went for a 25 mile ride tonight, and it's like having different bike. I would hit bumps, but wouldn't know it until I hit them with the rear wheel. Someone said upgrading the forks will show how poor the rear shocks are. That upgrade is a considerably more expensive venture.
Any way the forks worked perfectly, and no leaks.

Good to know. I have progressives front and rear, but I am still a little wallowy over bumps, if that makes sense. I think some firmer fork oil will then allow me to adjust the rears up more and ballence the bike better, ya know?

Yeah I hear ya. I actually backed off on the preload in the rear with the 440's and it is much better now.

Thanks K-Bob. I plan on doing the fronts with Progressive this winter. I really notice the front-end dive on this bike more-so than any other Brit bike I've owned in the past. The T-Square idea is a good one.

OK, since I don't own one, I'll ask. I've done some searching for "mighty vac", but received mixed results.

Could you post a link to the specific unit you used please? Any other ideas for alternative gizmos used to suck out fork oil or brake fluid are also welcome, thanks.

Regards,

Tom

Tom, Of course I spelled it wrong. "Mityvac" one word. I had no idea they had so many different products. All you really need is the hand pump, and the little 100 cc plastic catch can. Mine has the gauge on it which is kind of nice for looking for leaks in things but you don't need it for this process. Here is a couple of links I found.

http://www.mityvac.com/ Is their web site. The hand pump on the home page is the one I used. I think I have the brake bleeding and tune up kit with out the case.

http://www.tooltopia.com/index.asp?PageAction=VIEWPROD&ProdID=8121 This is basic kit I have but I bought mine at a local auto parts store and didn't get the swell case. The case would be nice.

I got one at an autozone I think. Not sure if it is the official mytivac or whatever, the idea being that it is a "vacuum brake bleeder." Sorta likie a Kleenex is a tissue...

Nice technique. However, why not just remove the forks? At least I found it easier to remove them, hang-em upside down, refill using the wooden dowel measurement technique, then reinstalling.

I've removed mine before too, but I can see not wanting to deal with possible alignment problems when re-installing the forks. That's a pretty good reason...

Take 'em off and hang 'em high. I let mine drain for an hour like an animal carcass while I did other stuff. It not only gets all the oil out but the goobers and sludge too.

Benny, The alignment issue is really not a big deal. Leave everything sorta loose then compress the forks a couple of times, then tighten the binders to specs. Those goobers were nasty too. The bitter dregs so to say.

I am in the market for a fork oil change one of these days, so I'll probably hang em hi also. There's a second story deck out back with a nail or two in it just lookin for something to hang from it.