I have a 2003 but I thought the engine was pretty much the same. Honda said it took .86 of one quart. Mine took all of the one quart.
You can download a xr80 manual here: http://www.torrentreactor.net/find/xr80-service-manual
about $120 dollars used. about $1,000 new.
Isn't an Xr80 a four stroke ? If so, there is no mix ratio, if it is a two stroke by some chance, I would say 32 to 1, so 4 oz of oil per gallon of gas.
4.5 quarts
3.2 quarts
No
about 5-15 hundred dollars
4.5 qts
4.5 qts. with new filter
Yes, it does.
5 quarts or until full on dipstick
10w-40 and it take 650ml of it