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III. ENGINE OVERHEATING:
The major causes of engine overheating are:
1. Improper break-in procedure.
2. Improper fuel/oil mixture.
3. Incorrect ignition timing.
4. Incorrect »park plug in use.
5. Spark plug incorrectly gapped.
6. Faulty points and condenser.
7. Dirt in carburetor.
8. Carbon accumulation in cylinder ports.
9. Excessively heavy oil in transmission case.
10. Tires underinflated; brake drag; chain too tight.
A. Improper Break-In. One of the most frequent cases of engine damage due to overheating is improper
break-in. There appears to be some confusion in the field about the necessity of break-in because some
2-cycle engines, such as chain saws and outboards, do not require it. IT IS IMPORTANT TO NOTE
THAT ALL MOTORCYCLES, REGARDLESS OF BRAND, REQUIRE ENGINE BREAK-IN.
• All motorcycle manufacturers specify break-in periods ranging from 250 to 2500 miles, depending upon
the type of engine used. Friction is greater during break-in until rings have had an opportunity to seat
and the cylinder wall has acquired a glaze.
• Bridgestone cycles should be run-in for a minimum of 250 miles. Sustained high speeds should be
avoided for at least 500 miles, preferably 1000 miles.
IMPRESS THESE FACTS UPON PURCHASERS:
1. Observe maximum, break-in speeds.
2. Avoid fast engine warm up.
3. Avoid fast shifting through the gears.
4. Avoid overloading.
• Once a Bridgestone cycle is broken in properly, it is the most trouble-free machine available as attested
to by the number of large rental operators who are discontinuing other makes in favor of Bridgestone.
B. Fuel & Oil Mixture. It is important to use the proper oils and correct mixing ratios. Always use a good
grade of regular gas mixed with a brand name 2-cycle oil (preferably Rockford Motor Oil), recommended
for air cooled engines. Never use special additive oils, or high ratio oils (50:1 or 100:1). Always use 15:1
ratio for break-in 20:1 thereafter.
C. Incorrect Ignition Timing. The next most frequent cause of overheating is excessively advanced ignition
timing. Because of its importance, carefully note and follow the timing procedures.
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