I've got a 03 400EX. I went for about 7 or 8 trips and changed the oil. It looked pretty effen dirty. I was thinking maybe i'd do it every 4 trips. What do you guys do?

I change mine every two "weekend" trips, or after a week trip. Probably overly conservative, but I think it's cheap insurance. You'll find a lot of opinions on this subject, so I wouldn't expect you will find a strong consensus one way or another.

You said your oil is "dirty". If you mean you had sand in your oil, you definitely need to change your oil more often. Some bikes get more sand in the crankcase than others, so the change interval is different.

In your case, I'd probably go maybe two trips, then do an oil change. Inspect your oil closely. If you feel you can stretch it to 3-4 trips, at least you'll know.

Also, keep your air filter clean every trip.

Every other trip for me on both my Banshee and my YZ450.

I change mine every 2 weeks.....a week usually conisists of....1 or 2 practice days at the track and a race or full day of riding on the weekends

You’d probably be ok every 4 trips if using full synthetic. If not then you’ll need to change it after every trip. However with that said it still depends on how you ride during the trips. Being an air cooled engine it’s harder on oil, especially in the warmer weather at the beginning and end of the season. Water cooled can get away with going a little longer between changes. I also change the oil filter with every oil change but if you don’t like spending the extra $3 for the extra protection you could do it every other oil change. So for my ’00 400ex my schedule is...

Winter Ridding:
Every 3-4 trips normal ridding with a few hard rides
Every 2-3 trips hard ridding with a few normal rides

Summer Ridding:
After every night ride trip if I do any ridding while the sun is up.

But then sometimes I get lazy and say screw it I’ll change it next weekend.

I change the oil in my yfz every 2 weekends, and clean the airfilter after every weekend.

I change the oil in my buggy every 2 trips, so I'll just start doing the quad at the same time. Thanks everyone. Troy out.

Change Synth oil every 3-4 trips.
Clean Air filter every trip.
Oil chain daily.
Check oil level daily.
Check/set tire pressure with gauge on first day, with foot rest of trip.

2 Yam 450s
1 Honda TRX450
3 Honda 400exs
1 Honda 300ex (will be for sale soon)
1 Honda TRX250

Geez, I get tired just thinkin about it. Next trip, my girls get a lesson on changing oil.

I clean my 400 oil after every trip. I do the same for all the spark plugs on our bikes. Keeps em runnin great. except that my banshees carb needs to be overhualed cuase shes starten to back talk.