Join Date: Mar 2012
Location: Yakima, Washington, USA
This issue flirts with being a myth. The fact that a broken belt will wreck a motor is true. However, I have been monitoring this issue for about 20 yrs and there is no credible evidence that a belt will break with reasonable care. Now I expect there will be several replies where someone knows someone who lost a belt...... I can accept that and still the maintenance frequency question persists. It is also true that organic materials will deteriorate with time and use under stress is another vector to break a belt. So In the past I came up with what I thought to be a reasonable and prudent way to judge the need for changing belts.
The formula for when to change a belt (is) = No of years old the belt is + Number of miles on belt/10,000. (XB = YR OLD + Miles/10k)
If the number for when to change a belt gets to 10 then you change the belt to provide reasonable care. Here is an example: I changed my belt in 2014, ie 5 years ago, and I have ridden 30,000 miles since the belt change. So; XB = 5 + 30,000/10,000, therefore XB = 8. Eight is less than 10 so the next belt change will be in 2 years if I do not ride the bike or sooner if I ride the bike many miles. Granted I still don't know the statistics for when a belt will break however I believe that using the formula will provide you with near 100% confidence that you are getting the value out of the belt without posing a threat to the engine.