First of all, I have a 2000 Big Bear 4X4. I am planning on changing all the fluids within the next week (oil, final gear oil, differential, etc.).

I have a couple of questions, do I really have to use Yamaha's oil, or can I use any quality motor oil (I happen to have 5 gallons of Castrol Syntec in the garage that won't be used otherwise)? Why/why not? Also, I notice in the schedule that adjusting the valves is recommended. Do they really need adjusting as frequent as recommended?

Any other comments/tips ver much appreciated.

I don't know about the valves but the owners manual says not to use any oil with friction modifiers such as multi weight car oils. They claim clutch slippage will occur.

Yeah I know, but I don't pay a whole lot of attention to that stuff - that would be too easy.

But really, I know in cars and trucks, you can't believe everything you read in the owner's manual service recommendations - I'm sure the same is true with these machines. As a matter of fact, I know 5 out of the other 6 ATV owners on my deer lease use regular 10W-30 motor oil and 3 of those machines are between 5 and 10 years old with no clutch problems, etc.

That's why I wanted some third opinions.

TXRam...I too have a 2000 BigBear. I'm running Mobil 1 Synthetic Oil and have experienced no problems at all, it seems to run a touch cooler with the synthetic. A riding buddy has a BigBear also, his cooling fan comes on more often when we ride trails or on the river...so either my temp sensor is messed up or the oil helped. Since we noticed this he started using Castrol Syntec, he hasn't had any problems yet, but he hasn't put that many hours on it since the switch.
I'm also running synthetic gear oils in the front and rear diffs. Don't know why...just thought it might be better stuff.
I say go for it.

As far as valve adjustments go, I had my 20 hr. service done at the dealership (which includes a valve adjustment) mainly to preserve my warranty. By the time my 20 hrs. had rolled around you could hear the valves clattering more then when it was brand new. So i'm gonna use my ears to determine when to adjust my valves. I'll probably check them when the manual says (which will be pretty soon) but they sound real good right now, so I doubt that I'll have to do any adjusting.

I have a 2000 Kodiak,I just had my first service done afew weeks ago.I would recomend you get the valves done after the first 20hours.The mechinic told me that the intake valve was tight on mine,my friend also has a Kodiak his were the same way.As far as the oil, wait on the synthetic until the machine has about 50 hours on it,the engine is still breaking,for the break in you want the engine to get to its normal temp.The synthetic will cool it a few degrees which is great once the engine is broken-in.good luck

Java
2000 Kodiak