Hi Bowhunter, Ive moved you post to the outdoors section as it seems to be the place for endless discussions about vehicles..

Good topic though. Have been thinking about a bike myself. 

I use a two wheeler a lot to go hunting.

Trail bikes in general are geared to go too fast for your average Kiwi hunter's need. so drop the front sprocket a tooth or two. Say down to 12 tooth up front. Makes them a lot more ridable, especially when coming back out with a couple of deer boned out in the pack on your shoulders.

Clutch. Most DR's XR's and AGs are cable clutch operated.  Keep them well lubricated (there's a do-dad available at bike shops that clamps to the cable and lets you spray CRC longlife or something else down the cable) You have no idea just how stiff a cable clutch is to pull in till you have ridden a modern trail bike with a hydraulic clutch

Bark busters are a given for a hunting bike. They are always getting dropped, so you have to protect your clutch and brake levers.

Lights on a trail bike rarely point the way you want to look at night. Also in lumpy going the stock light leaves a big shadow under the front mudguard. Led lightbars are a good idea, though check to see just how much DC power your bike makes. Its normally not very much at all. All trail bikes run 12 volt (sometimes 6 volt) AC to operate their headlight, and leds don't use AC

I now run a bike headlamp (from Aliexpress) through a recitfier and regulator to get 8.4 volt DC . I have a plug up on the handlebars so that when I arse off (not if ), I separate from the bike with the plug pulling free from the socket, instead of wires stretching and breaking.

ALWAYS carry a few tools for plug changes (drowned bike) puncture repair and CRC (again for a wet bike). Heavy duty 10mm wide zip ties will keep a flat tyre on the rim if you can't fix it yourself. Just travel slowly.

DR's and XR's and AGs are pretty bulletproof, though are also pretty heavy. XR's are an absolute pig to get started again when you have dropped them when they are hot Learn how to restart them before you are miles away from civilisation.
2 strokes can be quite a bit lighter in steeper terrain, though don't buy an ex motocross bike. Their gearbox ratios and motor characteristics are completely wrong for a hunting bike. Ag 100's and Mudbug 125's  are worth looking at as they are light and simple mechanical wise.

A 2 wheeler will get you into terrain that a quad bike can only dream about. They also use less gas, and are easier to carry to your hunting spot (rack on the towbar). BUT they can't carry the kitchen sink like a quad can.

For all the dramas of converting AC into DC for a led lightbar on your hunting trail bike, depending on how many times you think you will ride at night, it can be a whole lot cheaper and simpler to run cheap and nasty Chinese bicycle lights bungied onto your handlebars. This video shows the standard Mudbug headlight, (candle!!) then three bicycle lights. Two bungied onto the handlebars and one on a headlight headband. They run off their own batteries. total cost about 60usd. Fitting time. 1 min:)
Bought them 3 years ago. Still work fine.


https://youtu.be/YEbMZ4P-n_k

I've owned both. Still have my 1978 Mudbug 185. Absolutely no work done on the motor in 39 years and still going strong, if somewhat rattly!
The ag 2 strokes (yamaha and suzuki) from the 1970's and 80's were all mechanical oil injection so you didn't have to run premix. They are pretty simple systems, hence still going today. But the Ag 100 did have the injection pump in a vulnerable spot as the mechanic told you. The mudbug has the pump up behind and inside the engine casing from the countershaft sprocket, so is more protected.   The bikes would last forever, but forgetting to refill the 2 stroke oil container under the seat would always lead to a seized engine. Dairy farm bikes generally fall to pieces from corrosion from the cow poo and too infrequent oil changes.
Modern (2017 models onwards) 2 stroke enduro bikes have just gone back to oil injection, but electronically this time, and in different injection locations on the engine  to make the bikes comply with the latest Euro emission standards

if you get oil injected 2 stroke $120 to get an oil cutout fitted. we do this to all our ag100s as staff cant seem to check oil and saves a hefty repair bill.