This is a 2007 GS500F, with 8000 miles, gets 56 mpg highway, and burns about 0.15 ml of oil per mile. Runs very well, but the previous owner didn't follow maintenance schedule. I bought it two months ago and replaced oil, oil filter, spark plugs, and tires, and adjusted the chain. My winter plan is to drain the fluids, bring it into the living room, and do the following:

- Replace air filter
- Replace brake hoses and fluid
- Replace fuel lines
- Replace chain (current is nearing the spec limit)
- Check valve clearance

What else can I do to make to perform better? I'm usually a by-the-book-OEM kind of guy, so I don't modify or add upgrades.  However, I'd deviate if it's tried and true. For example, are there any unnecessary sensors or emission systems that limit the output?

That's a pretty good list already. I'd consider upgrading the front fork springs, especially if you're more than 150ish pounds. Even if you are sticking with the stock air filter and exhaust, you could consider rejetting the carbs. I don't think that's quite as necessary, but doesn't hurt.

I think the California bikes have a PAIR system that injects air into the exhaust to help with emissions. I don't think it does anything to hurt performance though.

I think that the benefit of higher flowing air-filter and exhaust is not enough to justify the outlay of time/money to get it set up right.  Even if it's dialed in perfectly, it won't be as reliable over the long haul as the stock set up because everything is dirtier and pushed harder.  If you want a bike that goes faster, it would be much more effective just to sell the GS and get a faster bike.

As Ed said, the best performance upgrades you can do on a GS are suspension mods.  The easiest of those being front end spring swaps, preload, and fork fluid weight and level changes.  Plenty of guidance out there to get things set up for your weight.  The next thing that many people have done around here is the R6 rear shock swap, which is plug and play in most cases it seems.

If you replace the chain, plan on replacing both sprockets as well. As the chain wears out, it wears out the sprockets to suit. Throwing a new chain on the old sprockets will just wear out the new chain at an increased rate.

Don't put stock rubber brake hoses back on. Go ahead and upgrade to braided stainless steel. Much better braking feel, and more robust then stock.

Add synching the carbs to your list.

Good point Slack. But put the carb sync after checking valve clearances - if you do it before the valves, swapping shims can throw the carb sync out.

Thanks folks. I'll let you know how it goes this winter.

1/2 a qt between changes with 8K, that actually may be worse than my first GS, tha t89 I had used 1/2 qt between changes @ 15k.
You cant maintain your way out of this. You're tolerances were loose from the factory. Nothing much helps. It gradually goes up.
I'd ignore it, and ride it. I've had GS'es that had 35K and barely used any oil. C'est la vie.
Cool.
Buddha.