Answers
There is a bobber type gauge to read and it has a wide range to read - there is a discrepancy - do you read the top or bottom of this guage?
I read it by the bottom. If you look at the line for "Full", there is enough room above the line for the entire float, so the bottom of the float is on the line when the tank is full. Most standard oil tanks are 275 gallons and there is no way to read it within a gallon or two. You are lucky to read it within +/- 10 gallons. The best way to read it is with a stick, or to know where empty really is. Most tanks suck oil out the top and the line is left several inches off the bottom so you don't suck up all the crud.
Progress so far
Bike Profile
Style - Bobber, stretched and lowered, drag bars, minimal look, single gauge small light front.
Colour scheme - Matt black, matt red twin stripes, satin black frame, polished alloy and chrome motor and accessories
Rough sketch of the style i'm after.
My names Mat i'm from western Sydney and i'm currently building my 1st XS 650 bobber. Its an 82 model and i'm pretty much doing all the work myself with the help of some mates, except for the welding, unfortunately that's one skill i haven't had a chance to learn yet but plan too in the future. For now ive gotten some help form an engineer out my way to get the hardtail and mounts welded on. Its still early days but its starting to take shape, here's a few pics!
Here's what the bike looked like when i bought it , not what i like at all but each to their own. The only parts i will be re - using are the front half of the frame , the forward controls, motor and headers, forks , wheels , guards and tank. The rest goes in the spare parts bin.

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News
Harley-Davidson rumbles for a comeback with new Blackline Los Angeles Times- Feb 24, 2011
Harley-Davidson rumbles for a comeback with new BlacklineLos Angeles TimesIn an attempt to rip itself off even more as Harley delves deep into its bobber past and declutters this modern-day machine, the speedo has been moved from the tank to the triple clamp. Instead of a gas gauge there is merely a warning light to stop, and more »- Feb 22, 2011
The Fishing Report — Feb. 25, 2011Record-SearchlightTHERMOLITO AFTERBAY — Bass action is non-existent but some shore anglers are drifting a bobber/worm down the channel above the Wilbur Rd bridge for steelhead. CLEAR LAKE — The bad news was it was very cold here, in fact it snowed. and more »