Daniel, I think that 16/40 would be pretty tall gearing. The KLR has a tall first gear even with stock gearing, so changing it by 12% over stock might make for some difficulty getting it going.
Three teeth in the back is just about equal to one tooth on the front, so 16/40 is about equivalent to 17/43. People do that combination, so it's not unheard of. I remember, though, when my 2008 was stock and I put a 16 tooth on it. Wouldn't pull the hat off my head and had to be downshifted for grades. I tried a 17 much later, after installing a 685, and did not care for it.
These things don't mind being spun up if they are in good shape, so don't be afraid to cruise it at 4500RPM. For off-road, even power line roads, you'll want stock gearing or lower. Nothing worse that stalling half way up a muddy incline. BTDT.
That it had only 1.5 quarts in it would tend to make me think that it burns a bit of oil. It's not catastrophic; they'll certainly live with that amount of oil in them. Kinda indicates that it might have been rode hard and put a way wet in its past life. Definitely keep an eye on it and, when you have a chance, pull the exhaust cam caps off and look for scoring. If it was ever run too low on oil that is the first place that damage shows up. No damage there, no harm done.
Strongly recommend reading up on Paul's oiling mods, just in case you find it does burn oil. If it burns oil all the time then Paul's mods may not fix that, but if it burns oil at higher RPMs I think you'll find those mods helpful. The basic mods are cheap and easy.
I'm pretty sure it was ridden pretty hard, if not, it struggled a bit. The original owner was a monster of a man. He was 6'7" and around 400 lbs. Friendly guy, but he was enormous. I'm not a small guy (6" and 260 lbs) but I felt tiny next to him. He bought this thing as a dirtbike
and mainly a dirtbike...so I'll definitely pull those cam caps off when I do my oil consumption check.
Daniel, With 75% city - 25% highway intentions and a power-line road up coming and "seems to be lugging below 4000 rpm" comment, I'm wondering if you are figuring 'backwards'?
If you wish to pep-up the response and amplify the torque you need to go the other direction with your numbers.
Stock 43/15 = 2.866 , 43/14 = 3.071
Raise the rpm per road speed, let the engine rev more freely.
ps, I got interrupted and Tom beat to it.
Shit, I was wondering why that seemed off. Thanks for pointing that out.
I was going to order that set on Friday and I would've been a bit annoyed if it was less responsive than it is now.
I'm curious what the revs would be with a 14T/44T set up. Again, I'm pretty conservative when I'm on the highway as is because people around my parts are terrible drivers!