I only use my bike for short trips. What should I do?
There are several things you can do to help your bike if you only ride short distances on it.
Use synthetic oil
Synthetic oil, specifically Shell Rotella T6 5W-40, is good for bikes that make short trips because it lessens the poor lubrication that happens on these bikes. Cold oil does not flow well, so when the engine is cold the oil doesn't move very well. Rotella is a fully synthetic oil with a very high film strength, which means it doesn't dry off of the metal parts easily, so it lubricates well even when cold. This will help reduce wear on your engine.
Take occasional longer rides
The next concern with short trips also has to do with oil, but it isn't something that is going to be helped or solved by using a particular kind of oil. This is condensation in the engine. On short trips, the engine will warm up partially but not fully. Then when you reach your destination and the engine cools back down, condensation can form in the open area within the crankcase. It's a small amount, but unless it's eliminated it can add up, and it can only be eliminated by bringing the oil to full temperature. So, while you're inside working your 9-5, gravity will carry the water down into the oil. Over time, the percentage of water in the oil will add up.
So, what can you do? Ride the bike. If you commute just a few miles a day, take the bike out on Saturday morning or take the long way home once or twice a week. On an average warm day, the coolant is warm in 3 or 4 minutes, but it takes as much as ten minutes of highway riding to warm the oil up. Once the oil is fully warmed up, all the mixed-in water will evaporate out very readily. A half-hour ride will reset the percentage of water to zero.
Change the oil more often
If you can't find the time to take the bike for a "full" ride on a regular basis, then you're going to have to consider changing your oil more often. In addition to reducing the oil's ability to lubricate effectively, water buildup will react with other things in the oil to form acids which will eat the engine metals. It's not really possible to tell how much more often to change the oil, but if you're serious about keeping the bike very well maintained, then you could do changes at about half the regular interval. But the absolute best thing you can do is simply find some time to ride it at least 15 miles at a time once a week or so.
Pay attention to the choke
Regarding the choke, the less of it you use the better. Obviously, you need it for cold starts and to keep the bike running when the engine isn't warmed up, but be conservative with it. When the choke is on, you're dumping a bunch of extra, un-atomized (liquid) fuel into the combustion chamber. Un-atomized fuel combined with relatively cool cylinder walls will result in lots of fuel washing down the cylinder walls. This washes away the thin film of oil that helps preserve the cylinders and piston rings. Also, you're running the engine rich, which can lead to spark plug fouling and carbon buildup in the engine. These are what you would call progressive conditions; they won't really come to your attention now, but down the road they can build up and cause problems.
When the engine reaches full operating temperature, it will clean off new carbon deposits automatically just by virtue of being so hot. Since you're not going to reach that temperature on a short trip, you want to reduce your carbon production as much as possible. Do this by using the bare minimum choke necessary to keep the engine running. If your normal idle is 1300 rpm, then use whatever choke it takes to hit 1300 rpm and no more. As soon as you can turn it off without the engine stalling at idle, do so. Even if it kicks around at only 900 rpm, if you can roll on the throttle without it stalling, then nix the choke.
Stabil-ize your fuel
Not putting a lot of miles on your bike will impact your fuel and fuel system. If you're only riding 6 miles a day, 5 days a week, that's only 30 miles per week. At that rate, assuming no additional trips, it could take you as much as ten weeks to burn through a tank of gas (YMMV). Fuel left in the tank that long is going to go stale and present problems which will require you to remove and thoroughly clean the carbs to fix. If you're going to regularly go more than 14 days between fill-ups, stabilize your fuel every time you fill up. Buy a bottle of STA-BIL and add the appropriate amount every time you fill the tank. STA-BIL keeps fuel fresh for up to a year and prevents gum and varnish buildup in the carbs.
Use a larger battery
When it's time to replace your battery, get one of the 9 amp hour or larger batteries available for the EX250. Stop-and-go city traffic will usually charge your battery just fine, but having more capacity is a good thing.
How you want your bike to run will determine how particular you are about how you service it. The kind of operating conditions discussed in this article are referred to as "severe" conditions. Severe conditions require increased care, along with maintenance at more frequent intervals. Following these guidelines will help increase reliability and consistency of performance, while decreasing the need for additional major maintenance and service in the future.