Shocking problem

oldman19

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This afternoon i decided to top up the oil in the rear shock preload adjuster, and on the advice from someone on another 1150gs site i topped it up with atf fluid. Luckily after assembly, i started to screw the preload adjuster in to check it was working better, everything working good until the last full turn of the adjuster when the seal on the collar above the spring went pop and spewed oil out everywhere. Question is: what did i do wrong, and can the shock be stripped to replace the seal. Glad it happened on the workbench and not on the bike. :confused::confused::confused:
 
What age is the shock? I believe the later ones might be serviceable but more knowledgeable voices will be along I’m sure.
 
The bike is year 2000 with 42000 miles. I had watched a video on YouTube where the guy used hydraulic jack oil, and the garage where i bought the atf oil said that's what they use. The oil i used was Dexron 2D.
 
When I think about it, there was a time, way back, when Honda recommended their ATF for use in bike forks, before fork/shock oils were available commonly. Many cruiser owners reckoned it reduce fork stiction too, but that was years ago, when addiitves were limited.

In these days of Dexron ratings for ATF ......... https://en.wikipedia.org/wiki/DEXRON .... these fluids have been formulated in a very specific direction, for the auto transmission of a car, not for bike shocks. If you trawl the internet, you will find mention of the latest Dexron ATF blowing fork seals in short order & it rather sounds like that has just happened to your shock. Seems like some seals are OK with it, some not & obviously the seals in your old shock could have been in poor condition anyway.

My conclusion would be that using ATF in the way you describe is best avoided, aside an emergency situation.
 
Overfilled??

I don't think they can be overfilled Mike

HPA's that I have seen are full of oil and don't have an air space ie; the preload on the slave cylinder only moves as much as the piston (master cylinder) capacity allows.

The seal (normally just an O ring) was probably failing anyway hence the need for topping up.

The BM shocks may be different but the hpa's that I've seen are generally retained by a small snap ring around the shock body which can be removed once the spring is compressed (the hpa probably has a small grub screw to keep its orientation on the shock body) this allows the hpa to be removed for disassembly.
The BM set up may be different.

I can't see oil type causing it's failure.

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