(1)  Small bits of carbon tend to build up in the area around the ring land. All of this section should be thoroughly cleaned of all debris.

We do all of the basic stuff, timing, plugs and that sort, but how often do you look inside of the motor of that bike with more than a few years on it. The only time we get into the top end, is when the thing is making so much noise that everyone sitting on the starting line stares at you when the bike’s running.

Then, and only then, will you inspect the piston and bore. Much of this embarrassment, and even some costly repairs, can be avoided if you take the time to maintain the top end at reasonable intervals.

(2) Using a piece of an old ring, you can scrape all of the carbon from the piston. Try not to remove any metal from this section. If the ring gets too loose in the piston, it will probably start to rock and soon break. Closely check the area around the ring pin. Most bikes seem to build up carbon in this area more than other portions of the piston.

Just as important as the shape of the top end, is the shape of the stuff that gets into the top end. If you’re getting dirt into the motor from a faulty filter, or from lack of care, the top end of the bike is going to suffer. Sure, over a period of running time, the piston is going to get a little loose, but the dirt brings out these problems quicker.

Nearly as bad as dirt, is the accumulation of carbon on the piston and the rings.

You’ll never be able to completely eliminate the presence of carbon, but there are a few ways to keep it under control. This entails removing the top end of the bike periodically to check for wear and cleaning of the piston, rings and the ports.

For this, we took an old 250 Maico, one that had been together for about two years, and had a lot of carbon because it had a lot of hours on it.

(4)  By standing the blade on end and moving it back and forth fast, you can remove heavy amounts of carbon in a hurry. Hold the blade close to the end, or it will start to chatter. Try not to scratch the top of the piston. If you do, it’ll cause hot spots and maybe further problems.

To clean the piston, both the dome and the ring land must have the crud removed. Check in the area where the plug would be firing and look for any corrosion of the metal. This’ll give you a good idea on how the motor burns. If the area is pitted, the piston should be replaced and the timing checked. Also, check for a lean condition in the carb.

If there’s a build-up of carbon on the very top of the dome, it should be removed. This can affect the manner in which the engine runs. All carbon from the top of the piston can be removed by using a razor blade, the single edged variety, and scraping the dome until all of the carbon is removed.

There are two good methods for doing this. Either use the blade as a cutting edge and slowly carve the carbon down by pushing; or use the blade as a scraper and run it straight up and down, moving it back and forth quickly. All of the carbon will come free using either of these methods, the latter being faster.

(6)  On the inside of the ring, carbon tends to pile up. The piece of ring used to clean the ring land will work fine in this area.

When doing this, be careful not to carve on the piston. Any cuts or scratches will cause hot spots, and in the long run, trouble. If you happen to scratch the top of the piston, get some 600 wet-or-dry sandpaper and buff off all of the scratches. DO NOT sand on the piston with paper any coarser than 600. It’ll make the situation only worse.

(7)  Our ring only needed to be cleaned and not replaced. Check for excessive gap and wear, if present, the ring should be replaced.

Once the top of the piston is done, clean the ring land. Any old ring for the same kind of piston works great. It doesn’t have to be the same bore size, since all you need is a section of the ring. Take the ring and sharpen one end on a grinder. Give it the shape of a chisel. Run the ring all around the ring land until the land is free of all carbon.

Use the ground ring in the position that fits into the piston; this way, the area around the ring will be the cleanest. Try not to remove any metal from this area. If the ring land is larger than the section of the ring, the ring will start to rock in the piston and will soon break.

The inside of the ring, where it sits against the dome of the piston, should be cleaned also. Use the section of the ring used to clean the piston for this. Keep scraping until there is no more build-up in the ring. Check the outside area of the ring for scuffing, or scratches. If the ring looks damaged, it must be replaced. Also, check the end gap of the ring in the cylinder before reinstalling.

Another section of the motor that seems to accumulate a slight amount of carbon, is the area right at the top of the bore. The top ¼" always seems to have a small layer of carbon that’s not real easy to remove. We used an X-acto knife with a very wide blade.

If you have a glaze breaker, or a hone, they’ll do a better job. Also, check for any gasket material that might have been forced into the bore when the head was tightened. If so, trim the edges away.

Cleaning the ports out is one of the easiest steps in top end maintenance. Simply because the only port that gets build-up is the exhaust.

To clean out our exhaust port, we used an X-acto knife with a very stout blade. It works fine for scraping out all of the build-up in this area. While the pipe is off, you have a great opportunity to clean out the head pipe and remove a great deal of the carbon that builds up inside the pipe.

For the head pipe, we used the X-acto knife again, but for the inside of the pipe you can heat the area and tap on it slightly with a blunt instrument. This’ll knock loose most of the carbon on the inside of the cones. Make sure you pour all of the loose carbon out of the pipe before you reinstall it on the bike.

After you’ve cleaned out all of the components in the top end, they should be thoroughly washed with solvent to make sure that none of the carbon is left in the ports, or in the barrel. Any debris left inside will work on the motor just like a handful of dirt.

Using these simple guides, you can maintain your motor much better and be rewarded with many more hours of running time. For your own bike, you should tear it down regularly, until you develop a schedule to follow.