Article [13] ST1300 - Final Drive Oil Change

Al Gully said:

What I like to do is mark the fill cap to the final drive casting before I remove the fill cap with a pencil mark, this way I don’t over over torque it with a 17 mm wrench
Fill cap is made of pot metal and breaks easily.
DAMHIK Don’t ask me how I know.

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Yup, very low torque values.

The service manual says to replace the Oring on the fill cap every oil change but I think few ever change it. So it’s compressed and deformed over time allowing the cap to come to on metal to metal contact with no feedback of snugging up. Honda completes the setup for cracking the cap by designing it to take a 17mm wrench or rachet handle that typically easily provides 4 times the torque value of 9 ft lbs. when a 17mm fastener starts pulling snug. The wrench handle is much longer than need be for 9 ft lbs. and no feedback.

Oldbikefixr said:

Wouldn't hurt to replace the o-ring on the fill cap. They do retain a permanent squash after a while and may lead to metal/metal contact around the perimeter.
Just a note....these caps are the same as the valve covers that were used on the old Honda small bikes.

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Mellow said:

I have no idea, never replaced one but good idea.

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Oldbikefixr said:

I used to replace a lot of these, back when I was restoring old Hondas. Seems pliers were the preferred tool for removing these caps.

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Mellow said:

Looks like it just pops off..

https://www.partzilla.com/product/honda/41306-MB0-020?ref=020baaea5d1b2643d87da4194111cbd27bc9639c

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You guys are talking different caps here. The vent (breather cap) in your post Mellow is not a fill cap.

W0QNX said:

You guys are talking different caps here. The vent (breather cap) in your post Mellow is not a fill cap.

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Yes, I know... we were discussing the previous post about how water could have gotten into the oil, so the breather cap is one possibility.

The o-ring in the filler cap is another... even some bad FD seals could be the culprit.

I would just fill and ride and check at the next oil change to see if it looks good.

Oddly enough the manual says replacing the crush washer on the drain plug is optional.

Mine did not have one.

I have spare aluminum and copper washers in a kit, but none of aluminum ones were the proper inner diameter so I put a copper on instead vs not having one at all.

Hopefully there's no metal interaction between the aluminum plug, body and the copper washer. I'm aware that aluminum deforms better than copper.

W0QNX said:

You guys are talking different caps here. The vent (breather cap) in your post Mellow is not a fill cap.

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I was referring to the large flanged hex headed filler cover. I have replaced the vent/breather caps on my ST's...don't like a rusty patina....which are press fit.