Belts, and Belt Failure


I’ll be the first to admit I don’t much believe in drive belts for motorcycles.  Gentlemen run chains. I suppose, if there were an easier way to deal with the length of the belt, that’d be one thing, but for me, I’m always dicking around with drive ratios, and thus sprocket sizes and chain lengths, so a belt just doesn’t make sense.  However, among a lot of other arguments for a belt, I was under the distinct impression that they’re pretty much maintenance-free, first, and second, never much failed except in the most dire circumstances.  That would be, age, or defective manufacture.

Well, over on EMF it seems there’s been a belt failure on a Zero.  Here’s that thread.  Curiously, it’s the same guy and same bike that had the bearing problems we saw a while back, and the guy he bought it from as a “race bike” told him to run the belt at significantly higher tension that the Zero spec – 40kg vs the 25kg Zero suggests.  So we have a belt running very tight, which fails, and also a motor with munched bearings.  Too much of coincidence, for my money.

In the process, though, a member posted a Gates white paper on both belt alignment specs and belt failure, which I’m posting here.  The alignment: Proper Alignment  …and the failure: Belt_failure_analysis_Final  – both fairly small PDF files.

Also, I found this.  The World of Timing Belts.  The_World_of_Timing_Belts

So, yes.  You need to check your belt tension, and check the condition of your belt.  Not to mention, I wonder what the lifespan of a motorcycle drive belt is…  a quick google and it looks like the Harley guys are running them in the neighborhood of 50k miles, with very little attention to the tensioning.  Funny though, I can’t remember the last time I heard of a chain breaking.



3 responses to “Belts, and Belt Failure

  1. We had Voltron pitted next to a guy with a Buell. He was espousing the virtues of a belt drive, and how our machine would probably benefit from one. That very next session he snapped the belt, and promptly packed the bike away and drove home. There’s a reason MotoGP bikes use chains too – they transmit boatloads of power and don’t break 🙂

  2. Ted belt life Harley’s is about 100 thousand miles biggest down fall of belt is havering a rock slip under and go threw belt so keep your gaurds tight too the belt 98 thousand miles here and still fine

  3. I’m new to belts, so we will see. I have had mostly shaft drive bikes. The last time I broke a chain was on a Suzuki 185 that had an acid spill on it. They are very durable in design.


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