Originally Posted by Sting32
I wont be the "last word" on this, everyone has opinions, I guess.
In my modern gasgas bikes, I run Castrol tts, 80:1, using a ratio rite cup to mix with. I DO NOT ride my 300cc Gasgas Raga Pro trials bikes, like most will ride a "dirt bike". I have done this since 2001. I have a good mechanic, who has had to fix things and he has never said "your cylinder" is showing signs of bad oil/fuel (aka lubrication/wear issues) knock on wood now.
Since the PRO model gasgas's trials bikes (since 03) the crank bearings are lubed via the transmission fluid, which is another reason you change the transmission oil VERY often... So, at least in my bikes, all you have is cylinder lubrication in a water-cooled engine.
In my air cooled bikes, I like to run at least 50:1 in those bikes, with the same oil. (this means it has more oil in the fuel).
Some run 50:1 in modern trials bikes, I dont think that is a problem, unless you start oil-fouling your plugs. so do what you wish, I think in that range... I know you should bias your gas:oil ratio by how or what you ride... If you tend to Motocross your trials bikes, then by golly use more oil in the gas, as in closer to 50:1 than 80:1.
Nice thing about trials bikes is, we're "idling" most of the day of riding, unlike other bikes and uses, where the bike will reach 1/2 to full rpms most of these same hours of riding, per day.
my Chainsaw, which when used is WFO most of the time I use it, will not take being mixed at 80:1, it likes a lot more oil because of how it is used. One chainsaw we had (old homelite) was 16:1 and lasted 25 years. new chainsaw is more like 32:1. my watercooled outboard motors like 50:1, since when you ride watercraft your duty cycles are usually wfo or near wfo most of the day. again it is a different duty the engine is being subjected too. Harder or more WFO the engine, the more oil you probably ought to use.