Alternator belt seems too short

[Tobias]

2004 R1150RT

 

Replacing the alternator belt but I can't get the new belt on.

 

I took the old belt off PN 7681841 and I am replacing it with the new one PN 12317681841 from the Seattle BMW dealer.

I brought the old one in for the parts guy to check the number.

I held the new one against the old one and noticed that it is smaller in diameter. He said it is because it hasn't stretched out yet and that the part numbers matched.

 

I've taken the plugs out and rotated the engine, but the belt still won't fit on over the pulley.

 

Any ideas?

[ron c]

I have the same bike and as I recall there was some confusion about the correct belt size.

I gave up on my dealer and went to Napa auto parts and bought their belt pn 25-040233. In fact I just bought a spare from them yesterday for $12.29.

 

Ron

[dan cata]

I have the same bike and as I recall there was some confusion about the correct belt size.

I gave up on my dealer and went to Napa auto parts and bought their belt pn 25-040233. In fact I just bought a spare from them yesterday for $12.29.

 

Ron

 

+1, that's what I do

 

Search for 4PK613 or 4PK611 an it will fit just fine

 

Dan.

[Boffin]

It depends which 1150 you have. The earlier ones use the alternator to tension the belt in the traditional way. Later ones use a 'stretch-to-fit' belt that is shorter new than when in service. The tension for this one is set by spacing the pulleys at a fixed distance - also used on the 1200 where the pulleys are fixed. If you have an upper pulley with no nut and a flat face (see the picture in this thread) then you have the new type elastomer belt.

To fit it, ease one edge over the pulley, then using either a wrench on the lower pulley nut, or by having someone turn the rear wheel with the bike in top gear, ease the belt over. Then tension using a lever under the alternator (being careful of the loom) until the spacing between the two pulley lips is about 4 1/2 inches - or close to. This takes a lot of tension.

I personally, fit the older style belts and tighten them to 1/4 twist tension. Much easier and no problems to date (86,000 miles).

 

Andy

[dirtrider]

Morning Tobias

 

As mentioned above your later 1150RT (2004 up) uses the elastomer belt from the factory. (elastomer belt went into production in July of 2003). Not all the 2004 up came with the elastomer belt from the factory due to parts shortages but the proper replacement belt IS the later elastomer belt.

 

On the elastomer belt the belt tension is set using pulley distance spacing not 90° belt twist or other feely type means.

 

They (BMW) has an expensive tool for installing that elastomer belt but you can do it yourself with a little prying and rolling the belt on by rotating the engine during the process. Two people can make the job much easier than doing it with just one person.

 

Getting the alternator back to the proper pulley spacing is quite a task as that belt has a lot of stretch to it. Until I did a couple and figured it out I would set the belt as tight as possible then after it was run in a while and stretched I would then set the proper pulley distances of 116mm between pulley flanges.

 

[Tobias]

Gents,

 

Thank you for your replies.

 

I'm going to try to fit the elastomer belt again, but if I don't get anywhere today I will pick up the NAPA belt tomorrow.

 

Regards,

 

Tobias

[Starfighter]

Boffin and Dirtrider have it correct.

As I recall there is a mark on the alt. cover that indicates which belt you should have.(but don't remember how)

Mine used the elastic belt and a wide screwdriver started it on, then I rotated the pulley to get it on the rest of the way.

The 90 degree twist method of tensioning worked for me also.

 

[dan cata]

 

[dirtrider]

___ As I recall there is a mark on the alt. cover that indicates which belt you should have.(but don't remember how)

 

Cover markings for belt type.

 

[Tobias]

Success!

After inventing some new swear words I was able to coax the BMW belt onto the lower pulley (by rolling the engine and using a flat head screw driver that I had ground smooth to change bicycle tires)

 

Thanks again for the help.

[dirtrider]

Afternoon Tobias

 

Did you then set the pulley distances of 116mm between pulley flanges? That is the proper setting per BMW.