RE: engine troubles
they recommend 25:1 for max engine life and for the lowest running temps.
i personally think that 32:1 is better because you get better performance but you need higher quality oil to do this safely. i use [link=http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.3312/.f]this[/link] oil. i am running the rest of my first gallon of fuel in my km baja. i used 25:1 for break-in but once i finish this gallon, i'll switch to 32:1. there are plenty of people at my LHS who have 5th scales and most run 32:1. one guy even runs 40:1 in his fs king kong. that klotz techniplate oil is very good and has 80% synthetic and 20% castor.
if you want to stay on the safe side (especially during hot summer days) run 25:1 but if you want a little more power, run 32:1 as long as you have high quality oil. 40:1 isn't too bad as long as it's not too hot outside and the oil is VERY high quality. For winter use, i think that klotz oil should do just fine in your baja at 40:1 as long as you don't tune it too lean. it is hard to tell when you are running lean when running gassers. with nitros, it is very easy to tell if it's lean. i was running my baja lean until one of the 5th scale "veterans" told me to turn the HSN 1/8 turn to the left and i got more power by richening. Gassers will happily run too lean without many symptoms so spark plug reading is one of the better ways to tune. I just run the factory carb settings to be safe. (for a km baja's engine, factory setting is dead-on. no tuning needed after that. not too rich or lean. the only problem is that it usually comes way out of whack from the factory and needs to be set to the specific settings. the HSN is supposed to be 1 3/8 turns out and mine was 4 turns out.)