Alternator belt size(s)

[KDeline]

Does anyone know if the belt size changed from 2007 to 2009? I have a used belt from a 2007 GSA with a number 12.31-7890 571-692637. From a 2009RTP is is 11.31-8528 385-163667. Seems like different size but close. From the RTP I have a constant bird chirp mixing with a loud intermittent scraping sound coming from the front of the engine. I thought it has to do with the belt. Alternator turns freely. 

06

11 31 8 528 385

RIBBED V-BELT - 4PK582

 Above is PN for RT and the GSA. I am wondering if the wrong belt was installed and on which bike?

 

[dirtrider]

53 minutes ago, KDeline said:

Does anyone know if the belt size changed from 2007 to 2009? I have a used belt from a 2007 GSA with a number 12.31-7890 571-692637. From a 2009RTP is is 11.31-8528 385-163667. Seems like different size but close. From the RTP I have a constant bird chirp mixing with a loud intermittent scraping sound coming from the front of the engine. I thought it has to do with the belt. Alternator turns freely. 

06

11 31 8 528 385

RIBBED V-BELT - 4PK582

 Above is PN for RT and the GSA. I am wondering if the wrong belt was installed and on which bike?

 

Afternoon  KDeline

 

Your 2009 1200RT should take the 11.31-8528 385-163667 that is a 4PK 582  (belt length of 582mm)

 

The 12.31-7890 571-692637 is a 4PK 592 (belt length of 592mm). 

 

If you suspect that your noise is coming form the belt then just remove the belt & run the engine to see is the noise goes away. (all the belt does is run the alternator so it will run fine without the belt for a while)

 

 

 

 

[KDeline]

I knew I could count on you DR. I replaced that GSA belt years ago as a precaution off of bike I bought new, seems like the wrong belt was installed from the factory. Not encouraging. So for now I put on the old 12.31 belt, the chirping is gone, need to ride a bit to see if the loud whatever sound is gone. Will order new belt. Thank you once again.

[KDeline]

I just noticed both the 11.31 and 12.31 are 4PK 582. Same size?

 

[dirtrider]

1 hour ago, KDeline said:

I just noticed both the 11.31 and 12.31 are 4PK 582. Same size?

 

  Afternoon  KDeline

 

Actually I don't think they are the same size (if you have an early belt), BMW had slipping issues with the early 12.31-7890 571-692637 so supposedly there was a belt length change on the later ones with no change in part number (I haven't ever personally measured them but some of early belts did slip, especially when wet).   

[9Mary7]

On 9/27/2020 at 11:43 AM, dirtrider said:

some of early belts did slip, especially when wet

Some of our authority bikes actually shredded those early stretch belts.... They did squeal when ridden hard.