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Standard fork bushing wear

kpke

kpke

Veteran
Joined
Apr 10, 2011
Location
Livermore
Moto(s)
many 2 strokes
06 R1 LE 158
Name
Ken
I am rebuilding the standard stock forks on the RZ350. I bought new bushings. I have measured the old and the new bushings and they are identical in thickness. The smaller ones on the left appear to have a bit of visible wear on the copper coating.

I am not so sure I need to replace these bushings. I can use them on another bike. These forks have approximately 10 K miles on them.

What do you look for and how do you know if these parts are worn out?

In both cases the new parts are on the left and the old on the right. The smaller ones are Yamaha parts and the bigger ones are seemingly knockoffs since they did not come with a Yamaha sticker with PN on them.

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I'd replace them since you're already in there, seems like a relatively cheap way to get peace of mind.
 
kpke said:
These forks have approximately 10 K miles on them.
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There's your clue. You got a ton of service out of a presumably OEM part and now have them disassembled. Slam 'em in there. I've replaced bushing on multiple bikes with identical OD/ID and they always run better.
 
They still look ok, the grey stuff is what tells you how worn out they are. If it's all rubbed off it definitely needs replacement. But yeah since you're in there might as well replace em.
 
Think of how many times per minute of riding that the bushings and seals are being "worked" and building up heat and friction. Even on a "smooth" road. Then ask your question again. Don't re-use bushings if you don't really need to. On the off chance you forget to service the forks you put the used ones in, or they are a second bike that doesn't really get ridden much, you'll regret it...
 
If the new bushings are OEM factory, put them in since you have it all apart.

If the bushings are aftermarket, don’t use them at all.
 
Fork bushings are coated with a anti friction material -the grey stuff which is generally very thin. If it is worn through to the copper or base material in any location, your bushing is shot. Yours look good to me.

You need to look at the inside of the narrow and the outside of the thick bushings.
 
you don't need to replace them, and the forks would be smoother with the old ones. Lindeman used to to "age" new bushings by scuffing them to improve function, do that if you are going to install new bushings.

as mentioned above, only look at the gray/teflon side of the bushing when looking for wear.....yours are good
 
I appreciate all of the replies!

I didn't know what to look for with regard to wear on these bushings. Now I know to look at the gray matter.

I'll bet there's many an old motorcycle out there with gazillions of miles on them that have never replaced these parts.

Ken
 
They look fine. I have only once seen a fork bushing wear out because it never had an oil change and also bent.

The only reason I've had to replace one otherwise was because it got messed up during removal.

Anyway those really look perfect still and I would reuse them.
 
Before you put the bushings back in, and if you want them as smooth as possible, burnish molybdenum disulfide powder or better, tungsten disulfide powder, into both the inside and outside surfaces of the bushings. Seriously. The stuff is vastly superior to Teflon and because of the gray color already on them, it’s probably been put on already.
 
My side gig is forks so I get to see a lot of them. The method many manufacturers tell you to separate the outer and inner tubes is to slide hammer them. Frequently the lower bushing try’s to slide under the upper bushing which scrapes a lot of the Teflon off. I just made it a rule if I’m taking it apart it gets replaced. If you’re in a situation where they are low miles and likely not too worn heat the area just below where the fork seal is to about 250 - 300 degrees and it will come apart usually with out damaging the bushing. They are actually worn out before the Teflon is gone. If you can see the copper color thru the Teflon it’s time to replace.
 
So they do use Teflon? Again, Teflon is completely inferior to molybdenum or tungsten disulfide powder. Not only is the coefficient of friction much lower, but the stuff works its way into the pores of the substrate it’s being worked into. It is the best anti friction material by far. Use it.
 
ST Guy said:
So they do use Teflon? Again, Teflon is completely inferior to molybdenum or tungsten disulfide powder. Not only is the coefficient of friction much lower, but the stuff works its way into the pores of the substrate it’s being worked into. It is the best anti friction material by far. Use it.
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If he puts any moly on these bushings it will just immediately disperse into the oil. There's really no point. The bushings operate primarily on an oil film with the Teflon as a backup.
 
The moly will stay on the bushings because it works its way into the pores of the bushing. Yes, some will get washed away, but what remains will stay there and protect the bushing from wear far better than Teflon. Teflon is a soft material and doesn’t hold up well to rubbing and abrasion.
 
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Thanks again guys. I'm in the camp that these are (still) good parts. ATM I'm going to put the new parts in this one and save the others for another fork if needed. As it's part of a fleet this bike probably won't get ridden much so I don't think it requires the additional moly friction reducer treatment. :thumbup
 
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