Alternator belt replacement question

[PETDOC]

I am replacing the alternator belt on my '04 1150 GS. I pretensioned the new belt by torquing the adjustor nut on the left side to 8 N-m then torqued the top and right sided bolts to 20 N-m.

Now my question--do I now torque the left sided adjustor nut to 20 N-m??

[Anton Largiader]

Does the alternator pulley have a plastic cap in the middle of it, or an internal spline? If so, you are using the wrong tensioning method and possibly the wrong belt.

[PETDOC]

Anton,

Thanks for the reply. I've got the correct belt as it is identical to the OEM belt I removed. I found a video for the alternator belt adjustment made by BMW for police departments using 1150's and I do torque the left sided nut to 20 N-m after tightening the other two.

[Ken H.]

Just to be sure we're 'on the same page'...

 

When you adjusted the left retainer, did you remove the in place retainer nut then install a BMW adjuster tool, or a capped nut (often called an acorn nut) to set the 8 N-m belt tensioner spec? The torque spec on that bolt is not meant to be on the permanent nut. Rather it is a method to turn the left bolt that is connected to the alternator's ratchet positioner mechanism.

 

So, after doing this and tightening up the other two bolts, you remove the tensioner tool used, then re-install the original nut on the left side and torque it to 20 N-m.

[PETDOC]

Ken,

I used the acorn nut with the spring to adjust the alternator belt tension to 8 N-m and after torquing the other two nuts to 20 N-m replaced the acorn nut with the original nut and torqued to 20 N-m.

I am curious as to what happens if you were to release the top and right sided nuts and then torque the normal left nut (not the special adjustor acorn nut) to 8 N-m?

[OoPEZoO]

Not being the nit picky type......Am I the only one that just uses a big screwdriver as a pry bar to set the tension on my Alt belt?

[outpost22]

Not being the nit picky type......Am I the only one that just uses a big screwdriver as a pry bar to set the tension on my Alt belt?

 

No.

 

Me too.

[OoPEZoO]

Not being the nit picky type......Am I the only one that just uses a big screwdriver as a pry bar to set the tension on my Alt belt?

 

No.

 

Me too.

 

OK.....cool, just checking

[PETDOC]

I had read of the screw driver technique with the preferred tension being one where the belt at its most flexible point can be twisted 90 degrees. Just out of curiosity is that the degree of tension you set it at?

[OoPEZoO]

I had read of the screw driver technique with the preferred tension being one where the belt at its most flexible point can be twisted 90 degrees. Just out of curiosity is that the degree of tension you set it at?

 

Yup, thats about it. hork (is that a word) up on the screwdriver until the belt it just tight enough to twist it 90 degrees at the middle with your fingers. 40K+ miles and I've never had a problem

[Mark K]

......Am I the only one that just uses a big screwdriver as a pry bar to set the tension on my Alt belt?

 

Whew! I guess I'm ok then. I tried the "scripted" procedure, but it didn't leave me with that warm, fuzzy feeling you get when you know you nailed it. I was much more comfortable with the screwdriver/twist method.

 

 

 

 

[Fugu]

hork (is that a word) up on the screwdriver until the belt it just tight enough

 

My '98 and my '04 both have adjuster thingamajigs that I put pressure on, belt tightens, I tighten other bolts to hold in place.

 

I don't have any acorn nuts or anything special I put on there just for tensioning.

 

Shouldn't your RT have such an arrangement? It's been too long for me to remember on the 98 exactly where/ how it is, but on my 04 it's an allen head on the rear of the alternator mount bolt that's at the bottom right as you are reaching in from the front. Pressure on that makes the alternator go up and the belt get tight, no horking involved.

 

 

[flars]

Yes - the adjustment bolt is right where you say it be. Unfortunately, getting a torque wrench on it is a toughie - that is why most people use the screwdriver/pry bar under the alternator, or the acorn nut (or doubled nuts) on the front of the adjustment bolt. The torque wrench is turned in the 'loosey' direction if the official adjustment method (i.e. from the back side of the alternator plate) is used. It is used in the 'tightie' direction if done from the front of the bike.

[Anton Largiader]

Anton,

Thanks for the reply. I've got the correct belt as it is identical to the OEM belt I removed.

 

OK, but the question was, do you have the plastic cap on the pulley, or (if it's missing) female splines in it?

[Fugu]

getting a torque wrench on it is a toughie - that is why most people use the screwdriver/pry bar under the alternator, or the acorn nut (or doubled nuts) on the front of the adjustment bolt.

 

Gotcha. I didn't even bother trying to stick a torque wrench in there but now that you mention it, I remember there isn't a ton of room.

 

 

 

 

 

 

[Tominator]

I bought the special spring loaded tool that screws on the end of the LH bolt. No guessing for BIG fingers. The new R1200RTs have a special socket that prys the belt over the pully!

 

Tomas

[davemc]

Why, yes, I did use a big screwdriver and tightened from there. Belt seated nicely. I had to use a Goodyear gatorback in a pinch. Since I have the bike apart to fix my leaking fuel QD's, I will inspect this belt after its first 5K miles.

 

[PETDOC]

My '04 GS has the same allen head on the rear of the left sided bolt, but BMW made a tool (acorn nut) that replaces the nut on the allen head bolt. When you torque the acorn nut to 8 N-m it raises the alternator to apply the correct tension to the belt, then you tighten the other 2 nuts (top and right side) to 20 N-m. After this you remove the acorn nut and reapply the regular nut with washer to left sided bolt and tighten to 20 N-m. Saves you from having to try and get a torque wrench to fit in the back side. I bought my acorn nut with spring from a German machinist on EBay for about $5 some time ago.

[PETDOC]

Anton,

I didn't look for plastic cap so I can't answer the question, but I'll check when I re-tension the belt in 6,000 miles. Regarding female splines, also did not check, but I presume so as the belt has about 4 deep groves on inner surface. If it helps my 04 GS was made prior to the change in belts which occurred with the manufacture of all '04 bikes after July 1,2003.

[Anton Largiader]

OK, that answers it. Thanks. Pretty early '04 then.

[PETDOC]

Anyone interested in the BMW videos on servicing the 1150 can go to this link (http://www.advrider.com/forums/showthread.php?t=143063) and click on one of four videos.

The V belt adjustment shows the use of the acorn nut in adjusting the alternator belt.