Hi Dunch

I've owned a 3AJ Tenere for 12 years and am currently 13 months into an Alaska to Ushuaia trip. Currently in Chile. I like your choice of bike!

Your fuel consumption does seem very high to me. On a quite heavily loaded bike, I am getting 12 miles per litre cruising at about 65 mph.
Also the top speed you quoted does seem a little bit low. Perhaps you need to rev it harder through the gears to get a better top speed? My rev counter is currently broken (!) so I can't quote rpm, but I change into 5th gear at 60 mph. Any lower than that and it seems hard on the engine/transmission. Personally, I wouldn't alter the gearing, as you are likely to find yourself on fast roads on occasions, and you don't want to be reving too high. I would clean the air filter and set the valve clearances. I would also do an engine compression test to see how worn the engine is.

As others have said, your cutting out in the rain is probably a problem on the HT side. First off, are the rubber seals on the plug caps still soft and sealing? Changing the cap is cheap (if you use an NGK plug cap) and easy.

You may or may not be aware of the famous 5th gear issue. I won't repeat the wisdom on this topic. There's lots about it on the HUBB if you do a search. If you've got a Mark 2 3AJ it's less of a concern than a Mark 1 or previous models, I believe. The Mark 1 had a black engine, the Mark 2 a silver engine.

As for spare parts, I think you're very wise to take a rectifier/regulator with you. I've had two fail on me in 10 years. The original fitted to this bike is very small and I presume heat eventually kills it. Later XT600e's had ones with cooling fins added, but they won't physically fit in the original position on a 3AJ. You could always fit one under the tail piece behind the saddle, extending the wires to reach. This has worked fine for me. Actually, now I think about it, it wasn't as simple as all that! I think I had to swap the positions of the wires in the plastic housing to suit the different regulator - so just be aware of that!

Other spares I would take:
If you suspension isn't top notch, then take chain rollers (inner and outer). I chewed through several sets of these on the first overland trip from UK to Australia. Now I have a good suspension set up and no problems here in 30,000 miles.

The Tenere was never imported into South, Central or North America (as far as I can work out). There are some grey imports, but Yamaha dealers only seem to have Tenere spares that are common to XT600e's. So you can get oil filters, sprockets etc, but not control cables (which are longer than on the XTe) So, I carry spare clutch and throttle cables.

I also carry spare brake and clutch levers, a CDI unit, ignition coil with HT lead, plug cap, wheel bearings, spare inner tubes and brake pads. The front brake pads do not seem to be common to any other bike imported into this region.

Hope this helps. Good luck with all the prep. I think it's the most difficult part of overlanding!
Mark