Wednesday, February 23, 2011

2001 BMW R1150GS Alternator Belt Replacement

This post documents replacing the alternator belt on my 2001 BMW R1150GS. Newer R1150GS’s use a slightly different belt and pulley, but the replacement procedure is similar. The major difference is the tensioning of the ELAST belt requires a different tool and procedure.

The tools I used:

2001 BMW R1150GS Alternator Belt Replacement

1993 through 2003 50A alternators:
Poly V: 4PK611, BMW part 12 31 1 341 779

Newer bikes:
ELAST: 4PK592, '04-on Oilheads and most Hexheads,
BMW part 12 31 7 681 841
ELAST: 4PK582, R12RT/Adv, BMW part 12 31 7 690 57

Stock BMW Belt for my bike:

2001 BMW R1150GS Alternator Belt Replacement

1) There are four nuts holding the alternator cover on. Remove them with the 4mm allen key socket.

2001 BMW R1150GS Alternator Belt Replacement

2001 BMW R1150GS Alternator Belt Replacement

2) The cover should pull out slightly and then down.

2001 BMW R1150GS Alternator Belt Replacement

Alternator belt exposed:

2001 BMW R1150GS Alternator Belt Replacement

3) Using the 13mm wrench, loosen the three bolts holding the alternator.

2001 BMW R1150GS Alternator Belt Replacement

2001 BMW R1150GS Alternator Belt Replacement

2001 BMW R1150GS Alternator Belt Replacement

4) Pull the alternator down to put more slack on the belt if it didn’t slide down itself.

2001 BMW R1150GS Alternator Belt Replacement

2001 BMW R1150GS Alternator Belt Replacement

5) Pull the belt off

2001 BMW R1150GS Alternator Belt Replacement

Old vs New belt:

2001 BMW R1150GS Alternator Belt Replacement

Mine was apparently past the 36,000 mile replacement. It was making a bit of a noise. Pieces of the belt had started to come off inside. Checking the belt tension is critical to belt life. Check when you change the oil.

Old belt:

2001 BMW R1150GS Alternator Belt Replacement

New belt:

2001 BMW R1150GS Alternator Belt Replacement

Notice the four ribs on the belt. They match up with the ribs on the pulley. Make sure to line them up when reinstalling the belt.

2001 BMW R1150GS Alternator Belt Replacement

6) The new belt just barely slipped back on.

2001 BMW R1150GS Alternator Belt Replacement

7) BMW has very specific belt tensioning specifications. Don’t be tempted to treat this like a car belt and do it by feel.

8) I had to turn the direction adjuster on the torque wrench to “loosen” not the tighten motion to get the alternator to lift.

2001 BMW R1150GS Alternator Belt Replacement

9) Using the 6mm allen key socket, extension, and torque wrench tighten the adjusting nut to 8 N-m. This will raise the alternator and pull it against the belt.

I found I needed to lift/tilt my gas tank slightly to have room with the torque wrench. See my air filter replacement guide for tips/photos.

BMW makes an adjustment tool that goes on the front rather than the back. Much Easier! I will think about getting it for the next tightening.

Adjuster for Poly V belts: tool 12 3 551, part 83 30 0 401 69

2001 BMW R1150GS Alternator Belt Replacement

10) While holding the torque wrench, use the 13mm wrench and tighten the other two nuts holding the alternator.

2001 BMW R1150GS Alternator Belt Replacement

11) Using the torque wrench and 13mm socket, torque all three nuts to 20 N-m.

2001 BMW R1150GS Alternator Belt Replacement

12) All three tightened up. Use the starter to crank over the engine a couple times, but don’t start it. This will help seat the belt on the pulleys. Loosen the bolts and repeat steps 7-11.

2001 BMW R1150GS Alternator Belt Replacement

13) Replace the alternator cover and tighten the four bolts with the 4mm allen key socket. The cover is plastic, so be careful not to over tighten.

2001 BMW R1150GS Alternator Belt Replacement

14) Cover replaced

2001 BMW R1150GS Alternator Belt Replacement

15) Check the belt again in 6,000 or the next time you change your oil.

16) Go for a ride!

 

Good pictures/discussion of the Poly-V vs ELAST here.

10 comments:

  1. That doesn't look too painful, not as painful as dealing with belt noise anyway. My car had belt squeal for a LONG time. The mechanic wasn't smart enough to know that it has two belts and didn't offer much of a solution. After puttering around under the car for a while it was easy enough to diagnose... a pain to access, but easy enough to diagnose. I'm glad to see other people out there do at least some of their own work.


    Brady
    Behind Bars - Motorcycles and Life
    http://www.behindbarsmotorcycle.com/

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  2. Brady: Thanks for stopping by! It was easier than I thought it would be. Almost easier than changing the oil in my SV which has to be the easiest bike maint I've done so far.

    Mine was also making a terrible noise that just kept getting worse. No fun.

    I try to do all my own maintenance on the bikes. It works out most of the time :)

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  3. Good writeup Chris, looks like exact same procedure I followed on my '04 R1150RT back when I still owned it.

    dom


    Colorado Motorcycle Travel Examiner

    Redleg's Rides

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  4. Dom: Thanks! When are you getting your third bike?? >:)

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  5. Dear Chris:

    Very nicely written up and presented. Even though I do not do my own work, I am a guy and fascinated by those who do. Interestingly enough, the alternator on the K75 is a beltless linkage with a ring of rubber "monkey nuts" to take up the slack.

    Nice blog today.

    Fondest regards,
    Jack • reep • Toad

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  6. Dear Jack:: Thank you! With my five bikes and my wife's two bikes, I am financially motivated to learn to do things myself. :) So that's why the ladies chase the K75... they want to see the monkey nuts.

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  7. Thanks for sharing this method, I used today and it worked great :) it was nice and easy, thanks again :D

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  8. Jantarek: Glad it was able to help out. Thanks!

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  9. Appreciate the helpful writeup...though its another tool to buy :( lower scale torque wrench...mine only goes down to 13.5 Nm

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  10. Tom Lewis: Hi Tom, glad you found it useful. I had to get a new torque wrench as well. I only had a 1/2" drive which didn't go below 20 Nm.

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