Since I’m going to need to do this, I thought it would be a great idea do do a little research on it first.  I found a great article at aa1car.com that explains these tests and how to interpret the results of a compression test or leakdown test. 

By the way, it looks like the testing equipment is available for under $40….that was good news.  Below is how they explain these tests….if you’re not familiar with them you should definately read this.

A compression test will tell you if your engine has good compression. An engine is essentially a self-powered air pump, so it needs good compression to run efficiently, cleanly and to start easily.

As a rule, most engines should have 140 to 160 lbs. Of cranking compression with no more than 10% difference between any of the cylinders.

Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.

HOW TO CHECK COMPRESSION

Compression can be checked two ways: manually with a compression gauge, or electronically with an engine analyzer the measures cranking compression. With electronic testing, a computer analyzer estimates compression in each of the engine’s cylinders by measuring slight variations in engine cranking speed.

The results correlate well with actual gauge readings, and can be completed in a matter of minutes without having to remove any spark plugs. What’s more, the analyzer prints out the results of the compression test making it easy to see and compare the actual numbers.

 

To check compression manually with a gauge, all the spark plugs must be removed. The ignition coil must then disabled or the high tension lead grounded. If the engine has a distributorless ignition, the ignition coils must be disabled to prevent them from firing. The throttle must also be held open.

The engine is then cranked for a few seconds using a remote starter switch or a helper while a compression gauge is held in a spark plug hole.

The maximum compression reading is noted, then the process is repeated for each of the remaining cylinders.

The individual cylinder readings are then compared to see if the results are within specifications (always refer to a manual for the exact compression figures for your engine because they do vary from

the ballpark figures quoted earlier).

 

IS IT THE RINGS OR THE VALVES?

If compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings.

If the compression readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings would tell you the cylinder has a bad valve.

A leakdown or cylinder leakage test is similar to a compression test in that it tells you how well your engine’s cylinders are sealing. But instead of measuring pressure, it measures pressure loss.

A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine’s firing order.

A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.

An engine is great condition should generally show only 5 to 10% leakage. An engine that’s still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.

The neat thing about a leakage test (as opposed to a compression test) is that it’s faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.

A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.

A cylinder that has poor compression but minimal leakage usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.

If all the cylinders have low compression but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.

If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).

 

 

Here’s some good advice I found today at http://motorcycleviews.com/general/restoreabike.htm.  I read tons of articles like this before I started on my CB360…but impatience got the best of me!!  For the CL200, I think I’m on the right track. 

Restore a Motorcycle

Sooner or later every motorcyclist gets an urge to restore an old motorcycle. Most don’t act on it. Some riders have a dream to restore an old motorcycle they’ve seen or remember from their youth. A few of these actually see the restoration through to completion. Here are some thoughts about motorcycle restoration and a few tips about how to do it.

I read a book called Rebuilding the Indian — A Memoir, by Fred Haefele shortly after I became an About.com Guide. Here’s an excerpt from a review I wrote about the book:

“The author was a 51-year-old tree surgeon, an ex-professor with an unsuccessful novel, when he decided he wanted to put $5,000 into a basketcase of Indian motorcycle parts. His dream was to convert the pile of parts into a restored 1941 Indian Chief motorcycle. You learn the process that one goes through to completely restore an old motorcycle but more importantly, you see the transformation of a restorer into a new man, a man he thought he would never become.” 

 I also found another book, The Restoration of Vintage & Thoroughbred Motorcycles, by Jeff Clew. This book was first published in England in 1976 and reprinted in 1996. It has 18 chapters covering: Finding a machine; The workshop; The Restoration Plan; The Frame and Forks; Wheels, Tires and Brakes; Seats; Gearboxes; Engines; Ignition Systems; Carburetor and Exhaust Systems; Accessories; Sidecars; etc.

Here are six tips I culled from this book to get you started restoring an old bike. Consult the book for all the details.

• Finding a Machine
  Get experienced advice from people who have restored motorcycles. Join a national vintage motorcycle club with many members. Decide how much of a restoration you want. Don’t buy a basketcase of parts because it may just be what’s left over after another restorer gave up. When you find something that interests you, don’t delay. It may be gone if you take too much time deciding.
• The Workshop
  Use what you have but make sure it’s warm and dry and you have a good workbench with a strong vise. The area should have adequate lighting and handy electrical outlets. Take inventory of existing tools and weed out those that may cause damage during restoration.
• The Plan
  Take detailed pictures of your bike at the beginning so you remember where all the parts go. Thoroughly examine the machine to determine what needs to be done. If the machine has scattered parts not attached, add them to the bike so you are sure what items may be missing. Assign boxes to major components as you disassemble to restore the bike. Make sketches and drawings of parts, electrical connections, etc. before disassembling. Decide what can be reused and what needs to be redone. Decide if you will do the individual work or have it done for you. Draw up a schedule to complete the various jobs. Be relaxed in the restoration but do stick to a schedule or it will never get finished.
• Engine
  If a spark plug has been removed before you bought the bike, be wary that the pistons may have seized. Special procedures are necessary to free everything up. Engine renovation may best be left to a specialist contractor unless you are experienced.
• Carburetor and Exhaust Systems
  Carburetors suffer the most wear and may need to be replaced. Be sure to take the old unit with you as you seek out a replacement. Previous owners may have the wrong parts installed. Be careful that the muffler system is solidly mounted and no air leaks are present.
• Preserving and Storage
  Most restored machines aren’t used that much. You need to store the bike in a warm, dry area. Always clean it after each use. Keep it locked up so it won’t be stolen. Don’t leave registration and other papers with the machine. Take special precautions with the battery and stabilize the fuel if you expect the machine to not be ridden for a long time.