Oil choice of Synthetic vs Petroleum doesn't matter: Synthetics are now mostly Group III severely hydrocracked petroleum (ever since Castrol won the lawsuit with Mobil 1), besides, MANY new vehicles come off the assembly line with a "Synthetic" oil. Yes, there are a couple of synthetics on the market that might be wise to avoid until the rings settle in...but, that's just a 100 miles or so.

Also, consider that this is a wet-sump bike (you'll get clutch debris in the oil), and thumpers have a reputation for being tough on oil viscosity breakdown...so, you'll probably serve your engine health better by frequent oil changes, not by using more expensive oil. Use a Hi-Flo or similarly highly-rated filter, and change it every few thousand miles (that should be every 3 oil change intervals, if you change oil every 1000 miles).

A little thicker oil may be better in this case, too, if you plan to extend your OCI beyond about 1000 miles...such as a 15w-40. Rotella fits this niche very well, and although it's classified as a 40 weight, it is only about 2 tenths of a Centistoke from being labeled as a 50 weight. It's cheap, it's JASO MA rated, and many of us old guy have been using it for decades without problems.

One other thing, if you truly want to maintain the best care possible: put a ThermoBob in your cooling system. The stock system allows gulps of cooled coolant to slam through your cylinder over and over. The ThermoBob has a bypass line as well as a slightly higher temperature thermostat, which does three things: 1) brings the engine temp up much quicker, 2) brings the engine temp up to a higher temperature at it's LOWEST point, 3) gently meters the cooled coolant through the cylinder, instead of gulp after gulp of cooled coolant. Some very experienced mechanics on the KLR650 (which has a similar stock cooling setup) report the cylinders of stock bikes get out-of-round relatively quickly, whereas the ThermoBob equipped bikes don't. I have one on my KLR650 as well as on my KLX331. Not all bikes benefit from this, as some have bypasses set up that allow sipping of cooled coolant (such as my CB919), rather than slamming gulps of it.

TIRES: Don't even ride on those tires/tubes at any speed you can't accept a blowout. They are dry-rotted. As far as what to get: DOT trials tires have become popular out here in the desert; if you're riding in mud and such...probably not so much. Kenda 270's are what I call "knobby trials tires" because they have a soft carcass like a trials tire, but, fewer *****, so, there is a bit more gap between *****. It's relatively inexpensive, lasts a good while on pavement, but, has the reputation for being a bit slippery on pavement...especially when new. I love this tire on my KLR650, but, I prefer a stiffer carcass on the KLX331 because I run the TuBliss system, complete with rimlocks, and can run the air pressure WAY LOW if needed. Also, if I got a flat on a trail that I couldn't or didn't want to repair, a stiffer-carcassed tire will ride out better. I do have a 606 on the rear of the KLX, and it's been good, I have a Geomax 71 on the front that has done well, too, but, it's not a DOT rated tire. Both are about ready to be replaced after 2500 miles, but, that's 90% HARD desert riding.

Great find on your bike! You'll potentially have lots of rubber bits to replace, and perhaps some friable gaskets in the carburator and petcock seals that may cause you some grief...but, once you get it all ironed out, you'll have a great little bike.

PS; well, it will be great after you do something about the hard compression spike in the front end. It really needs a different valve in there if you ride anywhere that has sharp bumps...you might get away with it if you are mostly on the road, and if you drop your fork oil viscosity down to at least a 5 weight.

 

Thank you for taking the time to with a very informative reply for me, very helpful. If remember correctly the old Yamaha enduro's 1970's came with Trial tires stock. Riding again 80% or more pavement and the rest trails no mud or sand. I do not plan on riding in the rain "I like to keep a clean bike".
Thanks Again!

Stashu

Moderators:--I also put the following in the new member area--If incorrect you can delete this--thanks!!
Additional:
Yes I am a new member and have not answered the questions BUT I feel some of the questions have nothing to do with bikes? I apologize :-) and some could be security question risk. Yes I work with security "in a way". Anyway here goes some that I feel are relevant. I hope the moderators accept this or they might have to ban me, But I hope not 
Thanks!.

Current bike :2006 KLX 250s
How many owned: about 14 total--not all at once :-)
How long riding: 40 + years
1st bike 1972 Kawasaki G5
Location:New York
Why am I here?---to have fun and learn and trade info!

 

My first bike was a 74 G5 100. I was in love with that thing!