Plug caps are the hard plastic pieces that go onto the spark plugs. They screw into the wires. The best way to check timing is get the radiator out of the way and take off the belt covers on the front of the motor. The belt pulleys have timing marks on them. There is a cap on top of the crankcase just behind where the fuel line comes out of the tank. Take the cap off, (about the size of a silver dollar) and turn the engine around until the T1 mark lines up. Both cam pulleys should be up according to the marks. If you don't have a manual, you'll need one and you can download it from this site. Paul
Oops, I thought you said plug caps. Dennis is right on the plug GAPS. He's also right about the timing. There is no distributor or anything to turn, the cam pulleys have to be in the right position to the T1 mark. There are "UP" marks on the pulleys but there is also a timing notch on the outside that lines up with the housing on the cover castings which is more accurate. The only thing that can mess up the timing is loose orbroken belts. You can check with a timing light at the T1 mark but you will also need a piece of plastic or glass to cover thehole to keep oil from spewing out. If the belts are in good shape and on right, you're good to go for a long time. I would change them around every 5 years or not more than 60,000 miles. You will get all kinds of opinions on this. Like we say, get a manual if you don't have one.