I'll first ask how many miles are currently on the meter?
Then I'll ask if your drive chain is or is not loose enough to lift the lower run Up to touch the rear tip of the rubber underslider?
If the chain can't touch it, when you set on it, it goes bow-string tight and robs HP.
Next what tires are you running & at what pressures? And how much do you weigh?
For reasonable fuel mileage I'll never recommend under 32 Front & 30 Rear regardless of brand & model of tire, but I might recommend More.
The 'choke' cable adjuster is under the fuel tank, dang them! The factory usually left them with too much slack.
Once the bike is running & warmed up, how far do you have to pull the enrichener lever before it affects the idle speed?
The cold start lever is NOT connected to a choke plate. It opens a separate fuel jet & air passage way.
If one opens the throttle plate even a smidgeon, it severely reduces the effectiveness of the cold start Enrichener Circuit!
Keep your hand OFF the RH grip and use your RH index finger on the starter button. And hold the button engaged for 5 full rotations of engine.
If it didn't start, let off the button & count to 10 to allow the raw fuel to vaporize, then engage the starter again.
The worst things we can do is 'play with the throttle' and 'tap,tap,tap' the starter button. IT will Not grind gears like a car starter.
You could even touch it at red-line! It would only 'spin-free'.
I live at 5000+ ft also. And I do know that a clean, stone stock KLR carb will work great from 5000 - 13,000 ft altitude.
And even quite well down to sea-level. They all came from the factory with the same set-up & can achieve 45-60 mpg if everything else is good.
But if it has been previously gunked up with old ethanol fuel, its needs a complete & proper cleaning.
Many people miss the 3 tiny low speed transition holes under the bottom lip of the throttle plate.
The Dyno-Jet brand jetting recommendations are TOO rich.
An un-oiled air filter can create an oil burner & cause low cold cranking compression, which can cause reluctant starting.
Tight valve tappet clearances, due to even normal wear can cause low CCC, which can cause reluctant starting.
The factory even got a few of the '08-'09 KACRs miss-timed, which can cause reluctant starting. (Which can be modified.)
Chances are high that your exhaust header to engine port Exhaust Gasket #11060-1108 needs to be replaced to reduce the 'after-fire' popping from the tail pipe.
Chances are high that no one ever re-torqued the header nuts by the 600 mile Break-in Maintenance & they may even be MIA.
But your FMF "silencer" will never muffle it as well as the stock muffler will.
There is a member on here by the handle of @Sarguy
who lives in Reno I believe who must be a pretty good home mechanic. Click on his hi-lited name & send him a private message, I think he might like another riding partner.