Specialty engine tools are not necessary for every vintage motorcycle restoration. But, sometimes, you absolutely must have the right tool for the job. One of the biggest problems for the home mechanic is performing unnecessary repairs. These repairs can come in the form of misdiagnosed issues or in damage caused from using an ill-suited tool. This work tacks time and costs onto a classic bike rebuild, and when it’s finished, you are no closer to your first ride.
Specialty engine tools can help us make only the necessary repairs for our restoration. Meanwhile, they are designed to protect other components from damage. The cliché is true: These tools really do pay for themselves over time. Let’s consider a few specialty engine tools that we offer, and see if we can determine whether or not you need one for your classic Japanese motorcycle restoration.
Compression testers are used to gauge the overall health of an engine’s valves and rings. For example, the shop manual for an engine with an 8.5:1 compression ratio normally prescribes a reading of 145 to 150 psi. But, the compression tester may only show 130 to 135 psi for a healthy, but worn, engine. We therefore know that our engine is in useable, though not ideal, condition. The valves and rings should be good for the foreseeable future.
One of the keys to using a compression tester properly is to understand that the specific numbers are not as important as how even the numbers are across all the cylinders. On a four-cylinder engine, a compression reading of 140-140-140-110 is a bad sign. The loss of compression on the number-four cylinder is evidence that the piston rings or valves are worn beyond their useable life. On the other hand, a reading of 135-140-130-135 would be a fairly typical and good reading for a bike with 30,000-40,000 miles on the odometer.
To get accurate readings, the engine needs to be at operating temperature, and the carb slides should be raised all the way to their top positions. Alternatively, the carbs may be removed from the bike. The manual for a bike with a 10.5:1 compression ratio will show around 170 to 175 psi as a roughly correct number – Each manufacturer is a little different. The combustion chamber shape and cam timing both impact the number. Remember, compression issues don’t heal themselves… They only get worse.
Should I own one?
If you like to work on your own bikes, or you are restoring a vintage Japanese motorcycle, a compression tester is a tool you’ll want to snag. There is simply no better way to assess the health of the piston rings and valves in an aging engine, short of a complete tear-down. The compression tester saves us from doing unnecessary work.
Leak Down Tester
A quick note: You will need an air compressor to use this pneumatic tool.
Rather than measuring the pressure the engine creates on its own, a leak down tester uses compressed air to pressurize each cylinder individually. This test will reveal any pressure leakage past the rings or valves. It even shows when pressure seeps past worn head gaskets.
To use a leak down tester, you must first thread the tool into the spark plug hole. Next, connect an air hose from the tool to the air compressor and pump 80 psi into the combustion chamber while holding the crank at TDC. The gauge will show you the percentage of leakage. A 3 to 5 percent leak down reading is okay, but anything more than 10 percent indicates that you have an issue.
At that point, you should listen to isolate where the air is escaping. If the exhaust valve is bent or poorly seated, you’ll hear air seeping through the exhaust. If air is escaping through the carbs, it indicates you have intake valve issues. When air passes through the crankcase vent, the culprit is the piston rings.
Should I own one?
If you have an air compressor, then the leak down tester provides more specific information than a compression tester. This information helps you determine whether you can remove just the head to work on valves, or if you will be pulling cylinder blocks off and replacing pistons and rings. Again, a leak down tester saves us from performing unnecessary work.
Put it on your Christmas list and look for a 12”x 6”x 6” box under the tree.
Piston Pin Removal Tool
Piston removal can be a source of frustration for even the most experienced motorcycle mechanics. Often the piston pins slide out easily, and in those cases, this tool is unnecessary. But, if a pin won’t push out with some simple nudging with your little finger, these tools stop you from damaging a connecting rod or main bearing by pounding on it with a mallet.
To use the piston removal tool, you must slide the tool through the piston pin and thread on the nut. The nut uses left-hand threads to ensure against accidental removal, so bear this in mind. Next, turn the exposed end of the tool with a socket or wrench, and voila. The piston is now much easier to remove, and there is no risk of damaging the rods, the pistons, your fingers or anything else.
Should I own one?
If you plan on rebuilding an engine and installing new pistons, this professional-grade tool can save some heartache. You may get away using alternative piston-removal methods for a while, but you will eventually damage something that you don’t want to break. There is nothing easy or cheap about a cylinder overhaul, so why add to the expense? Use the right tool for the job, and do each repair only once.