Rear diff didn't take much oil

Changed the rear diff oil on my ST1100. Old oil looked perfect, but service records showed it was last changed 24,000 miles ago. I really wish I had left well enough alone.

It didn't seem to take much oil. I have it level on the Condor chock on the trailer because it has been lowered so I can't get it on the centerstand by myself.

Would it be OK to try to add a little when it is on the sidestand? No oil came out when I removed the top plug, so I guess I'm not that far off, but I'm not out of the neck of the squeeze bottle. I tried to squeeze in more oil but it went everywhere. I'm afraid of an airlock somewhere.

No, there's no airlock possible. It doesn't hold much. (You did drain with the bottom plug and fill up to the bottom edge of the upper plug, right?)

That's what I did. I loosened the top bolt first, then the drain bolt. I didn't want to drain it out and not be able to refill.

About 150 cc is what it takes.

If your oil container has a tapered top/spout (Castrol synthetic gear oil style), get a 10 to 12 inch piece of clear plastic tubing big enough to slide over the spout firmly. This allows you to tilt the bottle while guiding the hose into the fill hole. Solves the mess problem. Top it up until you can see the oil is starting to rise on the threads of the filler bolt hole.

Did you know there is a small magnet fixed into the drain bolt? It is there to collect fine metal shavings from the gears. Inspecting that each drain will give you some idea of how well your chosen gear oil is working. I have found a full synthetic gear oil keeps it virtually clean.

It had no shavings and the oil looked brand new. Thanks for the tip.

jspringator said:

Changed the rear diff oil on my ST1100. Old oil looked perfect, but service records showed it was last changed 24,000 miles ago. I really wish I had left well enough alone.

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You really can't tell the condition of the oil by looking at it. You'd have to have it chemically analyzed. It's best to change it as called for by Honda (every 24k, many do it more frequently). Once you've done it once, it's no big deal. You're supposed to run the bike a few miles before you change it to warm the oil up and aid in draining. It only takes 5 ounces, so once it starts coming out of the upper fill plug, you're done.

Be very careful not to over tighten those plugs. There have been posts by guys who have sheared them off - these are not solid steel plugs.

SMSW said:

Be very careful not to over tighten those plugs. There have been posts by guys who have sheared them off - these are not solid steel plugs.

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+1. I'm one of those guys. The cap has an o-ring so it doesn't need to be tight to seal. Follow the torque specs and just snug it.

SMSW said:

Be very careful not to over tighten those plugs. There have been posts by guys who have sheared them off - these are not solid steel plugs.

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Also be careful loosening it off, although not sure what careful would look like in that case. Admittedly, my filler cap hadn't been removed for 17 years, but my bike is now stuck in the garage whilst I wait on a new $7 filler cap. Correction, two $7 filler caps.

KevinM said:

Also be careful loosening it off, although not sure what careful would look like in that case. Admittedly, my filler cap hadn't been removed for 17 years, but my bike is now stuck in the garage whilst I wait on a new $7 filler cap. Correction, two $7 filler caps.

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I would wonder about this - with something so fragile, unless you expect it to be seized up, by the time you think about trying other methods (heat, kroil, etc) you have a two piece cap. Was the rest frozen in the threads or did the O-ring just compress and provide so much friction that the head broke off? Good reason to change this oil only at winter layup time (but since you are cursed with year round riding weather that's another problem (grin)).

SMSW said:

I would wonder about this - with something so fragile, unless you expect it to be seized up, by the time you think about trying other methods (heat, kroil, etc) you have a two piece cap. Was the rest frozen in the threads or did the O-ring just compress and provide so much friction that the head broke off? Good reason to change this oil only at winter layup time (but since you are cursed with year round riding weather that's another problem (grin)).

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Most owners reinstall these caps without lubing the o-rings. If the perimeter of the hole is cleaned of all oil residue, then you get a really tight grip over time. Since they are o-rings, it's difficult for penetrating oil to well....penetrate.
Same/similar cover used on Honda tappet covers since forever. I have broken several over the years, and have learned to keep a spare or two laying around.

SMSW said:

these are not solid steel plugs.

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The same plugs Honda use on the old 750 to cover the valve adjustment... as mention it has an O ring , super tight is a NG