Rear preload adjuster woes.

[Guest]

I'm trying to get the rear suspension of my GS750 ('83) cleaned and back together and I think I have a shot or damaged preload adjuster....

I noticed when it was on the bike that it was set to "5" and I couldn't turn the knob at all....well to make a long story short and safe for the whole family to read I twisted the knob right off tonight out in the garage!

I had mounted the preload body in the vice since I couldn't get enough force on it just holding the part and once I had it all padded and socked down I grabbed the knob, gave it a good twist towards "1" and broke it. SO now I'm minus one knob, the aluminum broke where its keyed to fit the notched shaft.

Once I got that off I used a pin spanner to remove the slotted plate under the knob, no problem there...now the shaft was all loose and I was able to turn it all the way out by hand...except the preload indicator is still pointing at "5" and no amount of persuasion I was willing to try tonight would gat it to budge...

How does this thing work?!?! I can't see for the life of me how turning the threaded shaft that the knob goes on does ANYTHING to ANYTHING? Am I missing parts? Should there be fluid in the adjuster? I know there is in the line going to the shock because I made the mistake of craxking it loose....hope it can live minus a few CCs of fluid.

The factory manual seems to make no mention of the preload adjuster at all.

Thanks,
/\/\ac

[Macmatic]

Anyone have any info or links on the monoshock preload adjuster? I'm usually pretty good at figuring out how things SHOULD work but this has me stumped.

/\/\ac
'83GS750EF

[bradleymaynar]

I checked bikebandit.com, and it seems that the preload adjuster has been discontinued. You may want to Google and see what you can come up with. The aftermarket suspension on bikebandit.com just showed replacement springs for the forks.

Brad tt

[Macmatic]

I checked bikebandit.com, and it seems that the preload adjuster has been discontinued. You may want to Google and see what you can come up with. The aftermarket suspension on bikebandit.com just showed replacement springs for the forks.

Brad tt

Brad,

Thanks for your reply! I just took a look at it again and managed to make some progress (?).

I screwed the threaded shaft back into the adjuster body and gave it a good tug with some pliers....and out came the indicator! I'll have to look on BB and see if it shows detail on the adjuster...would have saved me some time if it does.

I now see how it works, the indicator in actually on a piston that gets pressed in when you turn the knob and the piston must move something in the shock body via the fluid... I'm missing some fluid though, none in the adjuster body so it may be plugged or just low.

Any idea what I can replace it with? I'll go with ATE SuperBlue brake fluid if no one has a better idea.


Thanks,
/\/\ac

[bradleymaynar]

I'm not real sure since my 1100 is a dual setup vs. your monoshock. It looked like your 750 also has an anti-dive setup? Sorry I can't be of more help, but I just thought I'd throw some suggestions your way.

Brad tt

[Macmatic]

Easy baby...easy.

So I've got it back together and working just fine.... simple really when I got down to it.

I drained out all of the old oil from the adjuster body, hose and shock body (not much there at all).

Next I mounted the shock in a vice, port at the top.
Attached the hose to the adjuster body, covered the end of the hose and filled the reservoir with ATE SuperBlue brake fluid. Then I let the fluid flow downhill until it was coming out of the hose and plugged it again.

Next I instaled the piston/indicator, letting a little fluid seep past my finger as it went in. Once the piston was in place I held the body so that the port was at the top and let it sit for a few sec, gave it a tap and squeezed the piston in until no more air came out of the hose.

Once I had the body and hose bled out I put the end of the hose under the surface in a small cup of brake fluid and drew back the piston slightly past #1 positon to draw in fresh fluid.

Finally I twisted the hose end into the shock body until it was almost tight, pressed the piston in until the indicator just touched the #1 line and locked the hose down.

Seems to work like a charm! I didn't measure but it looks like the shock body expands by about 12mm, as opposed to 0mm before.

So if your preload is gone, dig in! I'll post back if I have trouble in the future because of the brake fluid but I think it should be fine. SuperBlue is supposed to be fine for any brake system so I don't THINK it'll damage seals.

<edit> Just an update, four months and 2,000 miles or so later the preload is still working fine. I make it a point to cycle it once a week on "bike check day" to keep it from sticking again.

/\/\ac

[Macmatic]

<edit> Just an update, four months and 2,000 miles or so later the preload is still working fine. I make it a point to cycle it once a week on "bike check day" to keep it from sticking again.

/\/\ac

New update 4/1/2009:

I kept checking that adjuster for about a year and it always seemed fine and I stopped checking it regularly. Sometime in the last 18 months or so I've lost all the fluid out of the reservoir/adjuster again so I'm going to have to repeat this process. I'll be riding the bike back to NY in about six weeks when I move so I'm going to ride a few hundred miles solo and with a similar load to what I'll have when I ride North (camping gear, food, water etc) and see if I need to do this repair now or if it can wait for NY.

I'm guessing I rode most of last year with no adjustment there since I didn't change it after about this time of year in 2008.

I'll update again if I have any new info on the job, this was one of my first motorcycle projects so I've gained a lot (I hope) of knowledge since then.

/\/\ac

[derwood]

I used ATF instead of brake fluid, just backed the piston in , then clamped off the line after i had the master cylinder full, then attached it to the shock and released the clamp.