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Exploring Early Alternator V-belt Failure


KMG_365

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Had a very insightful exchange with our own Eric Sokoloff (HVAC guru) and got some great info. I had to google some definitions for some tech terms he used and in so doing I also found the following excellent article: http://www.maintenanceworld.com/Articles/mro/eliminate-belt-problems.htm

 

Maynard is overdue for his 108k mile service and I think my belt is also due. I'll try to post what I find out about the various causes I can eliminate. thumbsup.gif

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Jamie,

 

You two having what seems like more than your fair share of alt. belt failures, it will be interesting to see what you conclude.

 

One think that makes me take pause, what is your tightening procedure/technique/spec? Especially on your 'side of the road' change outs you are so fond of doing?

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From the article:

 

"As a general rule, sheave alignment on V-belt drives should be less than 1/2° or 1/10-in. per foot of drive centre distance. Alignment for synchronous belts should be controlled to within 1/4° or 1/16-in. per foot of drive centre distance."

 

I just replaced the belt on my '02 R1150RT, which had disintegrated at 26k miles. I checked the sheave alignment with a straightedge and found everything parallel but out of alignment by about 1/8 inch, with the alternator sheave set to the rear.

 

Is there an accepted way of shimming out the alternator sheave to make it all coplanar?

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Be aware that when the grooves are aligned, the front faces of the two pulleys are not on the same plane (my '02 built 1150). I don't remember the offset being as much as 1/8", but I was only doing a cursory check at the time.

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I replaced one belt at 50,000 miles and currently have 45,000 on mine. Probably change it in the next 5K!
It does seem to be an 1150 problem.
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Stan Walker

It does seem to be an 1150 problem.

 

On my '02 R1150RT I've replaced my belt twice, the first belt had 36,000 miles on it and the second had 33,000 miles. Both belts looked perfect when removed, no cracking, no missing chunks, etc.

 

It's just a problem on a few bikes. I suspect high electrical loads equal shortened life cycles for those who run several hundred watts of aux lighting all the time. That can double the work that the belt is doing. And of course any alignment issues will rapidly destroy the belt.

 

Stan

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It's just a problem on a few bikes. I suspect high electrical loads equal shortened life cycles for those who run several hundred watts of aux lighting all the time. That can double the work that the belt is doing. And of course any alignment issues will rapidly destroy the belt.

 

 

Add inadequate tension to the list & perhaps (as yet to be determined), worn sheave(s).

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  • 2 weeks later...
Hi Jamie! How many miles do you have on your current belt?

Well, I finally did my service yesterday and realized that I only had 15K miles on my belt and that I had already re-tentioned it after the first 6K miles . . . so I got lazy and didn't even look at it! dopeslap.gif

One thing that makes me take pause, what is your tightening procedure/technique/spec? Especially on your 'side of the road' change outs you are so fond of doing?
I started with the hex key/swivel/ext. asst. to the rear of the tightening lug (my beam-type torque wrench doesn't care which way you're turning it). I got a BMW nut/spring replica as a door prize at a Tech Daze and have used the BMW "approved" method (with the same results). I've used the tire iron levered up between the alternator and the engine block (same results again). The word from the HVAC experts are that looseness (and the associated slipping) is a primary culprit in what kills belts prematurely. I've been carefully tracking replacement and re-tensioning periods and in cross checking "twist" with known torque values on the adjusting cog think I've gotten the right "feel" for the proper tension. However, the temps in my garage vary from the 50'sF to 90'sF, and maybe I just rode the bike to drop the fluids hot or maybe the bike has sat overnight--so even the proper "approved" method will apply a different tension under different circumstances.

 

I don't remember ever hearing the belt slip, and perhaps the bearings in the alternator are too beefy to fail under too much tension, so I'm open to the fact that I might be applying too much tension to the belt. I'm doing Leslie's brakes for her tomorrow and it'll be very easy to check out her sheaves with the tank off. As she's never shredded a belt this early before, I'll be interested to see if the 114,000 miles has taken a toll on the sheaves at all.

 

On the side of the road swap outs (since the first one) I didn't touch the bolts at all, just slipped on the new belt and got back on the road. I noticed after repairing Leslie's this last time that hers was noticibly tighter after installation, which would make sense as the alternator would still be moved "up" slightly from the last re-tensioning of the old belt. I'm very curious to see what her belt looks and feels like after 3500 miles of being "too tight" (at least initially). I'll try to report back what I find out. thumbsup.gif

 

 

Thanks to everyone for the really good info in this thread! clap.gif

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Jamie:

 

I mostly ride in cooler climates and with a lower electrical load. I remember Doug "Zarly" Walker in Victoria had his belt fail at about 50,000km/31,000miles so I changed mine out at 47,000km/27,500mi. Mine had a chunk missing and probably wasn't going to last much longer. At 82,000km/51,000mi presently so I'll order one soon to take along and just replace it during the winter.

 

If you have an 1150RT I would suggest at least carrying a spare from 20,000 mi on and if you want to avoid roadside repairs replacing every 25,000 mi rather then the 60,000km/35,000mi in the maintenence schedule.

 

Mike Cassidy

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