BMWSportTouring BMWST DB
Page 1 of 2 1 2 >
Topic Options
#860699 - 11/08/13 09:46 PM R1150RT Poly Belt Replacement
Aussiegazza Offline
Member

Registered: 10/07/12
Posts: 127
Loc: Australia
I have a bit of a squeal when revving the engine sometimes.

I am guessing (only 30k on the clock) that it may be the poly belt.

Have a new belt and have the factory service manual, but thought I should ask for:

1. any suggested improvements while I am in there?
2. anyone replaced alternator bearings? If so where did you get the bearings?
3. do you really need the special tensioning
nut BMW No. 12 3 551? Any options? Where can you get one?

Thanks in advance.

Garry
_________________________
New 2003 R1150RT Owner

Top
#860725 - 11/09/13 06:41 AM Re: R1150RT Poly Belt Replacement [Re: Aussiegazza]
eddd Offline
Administrator
Member

Registered: 12/04/06
Posts: 4949
Loc: Hurricane, UT
I'll answer #2.

The alternator pulley is all that you can access when replacing the belt. Access to the alternator requires lots of disassembly. Since the alternator is an automotive design it is very robust. I can only think of one or two cases where someone had to address worn bearings. I parted out my '96 RT at 175,000 miles, and sold the alternate to a person who knew it had 175,000 miles on it.
_________________________
12 Kawasaki EX650
02 Kawasaki KLX300R
99 Suzuki DR650
96 R1100RT - forced retirement at 175,000

Parting out '99 R1100RT. Need anything?

Top
#860737 - 11/09/13 07:49 AM Re: R1150RT Poly Belt Replacement [Re: Aussiegazza]
dirtrider Offline
The Oracle
Member

Registered: 06/05/10
Posts: 7995
Loc: Ohio
Morning Garry

The 2003 BMW 1150RT is difficult bike to buy an alternator belt for.

The problem is-- the alternator pulley & belt design was changed in late 2003 production (July 03 or so) so unless you know what alternator pulley you have, or the bike's build date you really don't know what belt it requires.

The easiest way to determine what belt it takes (and the proper belt adjustment procedure) is to simply remove the belt cover & look to see what alternator pulley it has.

If a free wheeling (over-run) pulley then it takes the Elastomer belt, if a non free wheeling pulley (conventional solid bolted up pulley) then it takes the older Poly-V belt.

Type of belt also determines the adjustment procedure-- If the old poly-V then belt tension is the proper way (that's in you new manual).
If the newer Elastomer belt required then that is adjusted by the pulley spacing distance (not tension). (this isn't in you manual & if you are installing the Elastomer belt let us know & I will give you the pulley spacing distance)

There is (was) a way to tell belt type by front belt cover markings but that isn't always accurate as the front cover might be a replacement.

In any case-- If installing the Poly-V then you can set the belt tension using a torque wrench on the BMW special adjusting nut-- OR simply use a cheap M-8 acorn nut on the exposed adjuster stud.

Or if experienced with belt tension feel-- you can set the belt tension by CAREFULLY prying up the bottom of the alternator then checking the belt tension with a 90 twist (you need a good base feel for this method though). If using this method you need to be VERY CAREFUL to not damage the wiring running under the alternator.

If your bike takes the Elastomer belt then neither the special BMW adjustment nut or the acorn nut will do any good as the belt tension is just way too high for either to work.

On the Elastomer belt, I set belt pulley spacing with a tool I made to force the pulley's apart to the proper spacing. Some do it by prying on the bottom of the alternator to a pre marked alternator position but that is risky due to the belt tension required & soft alloy alternator housing.

I have seen quite a few of the Elastomer belts set incorrectly due to the belt installer trying to use the old torque method, or simply thinking the tension required to set properly feels way to high to them (those Elastomer buggers are REAL tight at proper install tension).

As for doing anything else while in there?-- not much to do other than look for oil leaks & visually inspect the area.

That alternator is a REAL PAIN to remove to replace any parts on it as it comes out the rear so the ABS system, Motronic, etc needs to be removed first. Just give the alternator shaft a spin & if the bearings don't feel rough, gritty, or growl then don't mess with it.

Added: Free wheeling pulley shown below---


Edited by dirtrider (11/09/13 07:50 AM)
_________________________
D.R. ___
Sent from my rotory dial wall phone!

Top
#860820 - 11/09/13 05:10 PM Re: R1150RT Poly Belt Replacement [Re: Aussiegazza]
Aussiegazza Offline
Member

Registered: 10/07/12
Posts: 127
Loc: Australia
Thanks all.

I know the build date and have the belt.

The M8 acorn approach seems to be the go. I felt that the special tool was an acorn nut with a spring to keep the bolt in correct position, and you have confirmed this.

Another option could be 2 M8 nuts locked together (but this may slip).

Knowing the nut size is a big step up to cobbling a tool together.

Won't be doing until after XMAS as we are on holidays shortly.

Garry
_________________________
New 2003 R1150RT Owner

Top
#861011 - 11/11/13 06:10 AM Re: R1150RT Poly Belt Replacement [Re: Aussiegazza]
Jim Moore Offline
Member

Registered: 12/31/00
Posts: 2427
Loc: Jax, FL
You can also do it by just jamming a big screwdriver under the a;ternator and lifting it into place. With a poly-V belt that is.
_________________________
Jim Moore Jax, FL '99 R1100S '02 R1150GS

Top
#861012 - 11/11/13 06:17 AM Re: R1150RT Poly Belt Replacement [Re: Aussiegazza]
AndyS Offline
Member

Registered: 11/03/02
Posts: 3743
Loc: Somerset, Great Britain.
So does anyone have the dimensions of the pulley to pulley measurements for the Elastomer belt?

Top
#861014 - 11/11/13 06:20 AM Re: R1150RT Poly Belt Replacement [Re: Jim Moore]
roger 04 rt Offline
Member

Registered: 11/27/11
Posts: 1844
Loc: Massachusetts
I have no idea how I did it, but using a torque wrench I managed to strip the gears on the part of the adjuster attached to the alternator. The alternator tends to bind when adjusting it and I was only trying to see if I was at 8 NM per the spec. For the time being I will have to estimate tension like I've done with every other belt before. Tight but not too tight.

My bike has the older, not elastomer belt as it was produced in January 2003 but is called an '04.
RB

Top
#861020 - 11/11/13 06:46 AM Re: R1150RT Poly Belt Replacement [Re: AndyS]
dirtrider Offline
The Oracle
Member

Registered: 06/05/10
Posts: 7995
Loc: Ohio
Originally Posted By: AndyS
So does anyone have the dimensions of the pulley to pulley measurements for the Elastomer belt?


Morning Andy

The pulley spacing distance to properly tension the Elastomer belt is 4.66" (118.5mm) between the pulley ribbed surfaces (that the belt rides on) or appx. 4.5" (116mm) between the pulley front flanges.

The outer flange to outer flange measurement is MUCH easier to do but obviously not as accurate as those flanges are not a controlled surface so could vary a little from pulley to pulley (still close enough though)
_________________________
D.R. ___
Sent from my rotory dial wall phone!

Top
#861034 - 11/11/13 08:29 AM Re: R1150RT Poly Belt Replacement [Re: Jim Moore]
roger 04 rt Offline
Member

Registered: 11/27/11
Posts: 1844
Loc: Massachusetts
Originally Posted By: Jim Moore
You can also do it by just jamming a big screwdriver under the a;ternator and lifting it into place. With a poly-V belt that is.


Someone can check my numbers but here is how I calculate the forces for the screwdriver approach.

Radius of driving gear: approx. 3/8 inch.
Spec of tension: 8 NM which is about 70 inch-pounds

Upward force on altenator = 70 divided by 3/8" equals about 180 lbs.

Use 15 inch bar contacting the alternator 3 inches up pushing at 15 inches is 5 to 1 force advantage means push bar with 180/5 lbs force means 36 lbs force on end of bar, quite a lot.

Maybe my math is wrong.

Top
#861039 - 11/11/13 08:50 AM Re: R1150RT Poly Belt Replacement [Re: roger 04 rt]
dirtrider Offline
The Oracle
Member

Registered: 06/05/10
Posts: 7995
Loc: Ohio
Morning Roger

That 8nm on the adjuster nut has to take into account the stud friction as well as the gear drive ratio of the adjuster stud.

I'm not sure you can directly equate adjuster stud torque to alternator lifting force without physically doing both then marking the alternator position & compare.

If a Poly-V belt just use the 1/4 (90) belt twist method.
_________________________
D.R. ___
Sent from my rotory dial wall phone!

Top
Page 1 of 2 1 2 >