'84 Ninja 900 rear suspension play

[84ninja900]

I've been rebuilding my Ninja and have a question about play in the rear suspension. When I inspected the suspension linkage I found that the lower shock bearings and sleeve were bad, so I replaced them. All of the other bearings and sleeves looked good so I just cleaned and regreased them. After I reassembled everything I found that if you push up and down on the end of the swingarm, there is still around 2-3mm of play. The manual doesn't have any info on this, so I'm wondering if this is normal or if I need to replace the rest of the bearings and sleeves?

[elr658]

You ain't done yet.

[Lawn Masters]

got more bearings to replace I think.

[oldcatman]

My '84 Ninja has about 14,000 relatively easy miles on it. It too shows about 2-3mm of vertical play at the end of the swing arm after cleaning, inspection re-greasing and with all pivot bolts torqued to specifications. I can detect no play at the swing arm bearings by twisting. Play in the main swing arm bearings would bother me. As for the vertical play from the linkage, I'm calling it good for now.

There are 5 bearings (not counting the swing arm bearings and counting the two linkage arms to the swing arm as only one) that contribute to the vertical play we are seeing. The swing arm adds a mechanical amplification of about 5 to the combined play from these bearings. Each bearing (except the two shock bushings) has needle bearings with an inner sleeve and a shaft running through the center of that (more play). Do the math and you'll see that as a first approximation, if you've got .004" of play in each of the bearings you'll see the vertical play we are seeing at the end of the swing arm. I'm guessing that if you replace everything it isn't going to make much difference, but its just a guess. Bottom line is that this play will only show up when the suspension bottoms out or if the swing arm somehow tries to extend faster than the shock can follow it.

If you do replace everything, I'd be interested to know if it helps, and probably of more interest, for how long. Good luck and keep at it. Sounds like you are going to beat me to the finish.

[84ninja900]

Thanks for the replies. I took a closer look at it today and it looks like alot of the play is coming from the upper shock mount. I can see the top of the shock move up and down slightly when I move the end of the swingarm, which I know isn't good. It looks like the inner sleeve on the upper shock bushing is not being pinched between the mounting flanges on the frame when the bolt is torqued, so I think I'll try making a shim washer to take up the extra space between the sleeve and the flanges. I'll post up the results when I'm done.

oldcatman, thanks for the info and encouragement, but I wouldn't be too sure about finishing before you. I've got lots yet to do and I keep getting distracted by other projects.

[84ninja900]

Well I've shimmed the upper shock mount, which took care of the play I was getting there and that made a big improvement in the suspension system play. I'm now getting about 0.012" of vertical play at the end of the swingarm, which doesn't seem too bad to me. Using oldcatman's logic about the bearing clearances, this would give an average clearance of about 0.0005" for each bearing. That seems reasonable so I think I will leave it and see how it works. Thanks for everyone's comments.

[Lawn Masters]

btw, GREASE the upper shock mount. This WAS my original upper shock mount on my 1000R, the zerk fitting to grease it was MIA, whcih caused this to happen.



these "were" my bearings once.