Click on a pic to enlarge:

Click on a pic to enlarge:

Triangle shaped side, battery box built into it. The drain plug (704) is on the left side of the bike on the side near the bottom of tank.
The oil filler neck is shorter than the -80 tank and is hidden behind a removable cover which also hides the battery.
The frame has welded on hooks to attach the cover up top with a screw on the bottom into the frame.
The left side is exposed without a cover and has a “Made in USA” transfer emblem in the center.

It's not clear what the actual oil amount is for the tank.
The 1979 owners manual shows a pic of a sight tube on the left side of the bike on the front edge of the oil tank.
The cap does have a dipstick but here is the Owners Manual instructions on checking the oil;
With the motorcycle on upright, there will be 1/8“ of air space at the top of the tube when the oil tank is full (3 quarts).
With the bike on the jiffy stand, the tube will be full (no air space) when the tank is full.
With the bike on the stand and the tank with only 2 quarts, there should be a 1-1/8” air space in the tube.
The sight tube never shows up in the parts manuals from 79 thru 85.

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Oil Tank Cover Mounting Brackets on the Frame:
The 80-81 frame will not take the 79 cover.
The 79 frame has welded on tabs for that cover (third pic below) , and a welded in place nut for the bottom mounting bolt, that the 80 frame does not have. ⁶⁾

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Triangle shaped side, battery box built into it. The drain plug (704) on is on the left side of the bike at the bottom.
There is an extra mounting tab welded to the top inner side of the tank in front of the vent nipple.
An “L” shaped bracket (66279-80) is attached there that is slightly curved on the end with a pad under it as a hold down point for one end of the battery strap.
The left side is exposed without a cover and has a “Made in USA” transfer emblem in the center.
The oil filler spout is higher up on the 80-81 than the 79 tank and the right side cover (66601-80) has a molded cutout to go over the spout and also exposes the battery.
You can check oil level and fill the tank without removing the cover.

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79-81 tanks are 15“ between the hole centers. ¹²⁾

Mounting tabs repaired on a 1980 frame:
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