New fork seals bad?

MARK IT

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#1
I have a 89KX250 and have just replaced the fork seals
just recently and road two enduros on them, we wen't and
raced moto X and after two laps the left seal is leaking, whats
the problem. I used ATF for fork oil (don't say this is the problem
unless you are sure) and had it at the recomended level.
 

RM_guy

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#2
I doubt the seal is worn out. There is either dirt trapped under the seal or you have nicks in the inner tube.

The dirt is easy to fix by sliding down the dust seal and spraying contact cleaner at the oil seal to dislodge the loose dirt. Then take some cardstock or heavy paper and carefully slide it under the seal to remove debris under the seal. It may leak a bit while doing this but it will stop.

A nick or scratch in the plating of the inner tube is more difficult to fix. Sometimes you can polish out minor scratches. Don’t get it too smooth though since some surface roughness is needed to retain oil for lubricating the seals. If the nick is completely through the plating, you’ll need new tubes.

Good luck
 
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#3
Im not sure, but using Automatic Transmission Fluid in a fork is just not a good idea! The valves and passages in a fork are extemely small and require usually a 5 weight, not 30 or 40 weight oil! The internals of your fork may damage quickly with that oil. I think the reason that your seals went, was because when the oil was forced thru valves the oil put a lot of pressure on the seals before being able to move through. Fork oil is worth its weight in gold compared to ATF for the same job.

Also, if you have a nick in your fork tube you could get the tube replated if necessary. I dont think theres a limit to how smooth you want the inner tubes, they dont need to hold oil like a cylinder because the tubes are bathed in oil.
 
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RM_guy

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#4
Originally posted by FMX_novice
...I dont think theres a limit to how smooth you want the inner tubes, they dont need to hold oil like a cylinder because the tubes are bathed in oil.
The IS a point where the tubes can be too smooth. For any oil seal to function properly there has to be a thin film of oil between the seal and the surface you are sealing against. If there was no oil, the seals would stick to the tubes and tear. Not a good thing. The roughness of the fork tubes doesn’t have to nearly as high as the engine bore but you still need something.

When polishing the tubes, compare the “shininess” of virgin sections of the tube and don’t exceed it.
 

MARK IT

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#7
Well I removed the dirt with my fill'er guage, there was more than I thought
ther would be. I haven't tryed it but I'm sure this will solve the problem.
Jeremy, is there a easy way to remove and add new ATF to the forks
on this model (no drain screws and spring is bolted in). say if I rigg somthin
to vacume out the old oil?
FMX, ATF is 7.5 wt and I've used this for years with no problems, but if I do
install new seals I may go to some Bell Ray.
 
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#8
The 89 KX was the only year of the 46mm upright forks that have attained cult status popularity among some. The easiest(only?) way to add oil is to remove the caps on top of the fork and remove the springs.
 
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#9
If there is some dirt stuck in the seal, take some old film negatives slide it along the tube past the seal..