R1150RT, Alternator Belt Adjuster Unit Broke

[Softtail]

I have about 27k miles on my 2002 RT and decided that I would attemp to replace the alternator belt. I took off both right and left fairing, shark fins and cover and replaced old belt with new belt. Everything went great untill I tried to adjust the belt tension. My aftermarket shop manual had a rather poor photo and even poorer description of how one goes about adjusting the belt tension using a torque wrench. Eventually I figured out where the adjuster was but not how to get a torque wrench into the space where the adjuster lives. My wrench was just to big. I kept trying, using various combinations of universal joints and extensions, untill I managed to break the adjuster in half. The adjuster is a little nut/gear combo unit. I gave up on the torque wrench idea, took a very large combination screw driver pry bar and lifted the alternator untill I felt the belt tension was about right, tightened things up and put the bike back together, sans the nut/gear unit. Over the next several days I rode the bike to Portland OR and back, about 700 miles. No squeaks or squeals, everything seems to be fine, I hope. So, my question is, do I really need the nut/gear adjuster? <<<<Softtail>>>>>

[ShovelStrokeEd]

No you don't. I have never used one. A nice small tire iron will fit under there and pry things up just as well.

 

At 700 miles into the new belt, you should probably go back in there and, at least, recheck the tension. It is one of the steps in the 600 mile service and should be repeated 600 miles after the belt is changed.

 

The 90 degree method works just as well for checking the tension. You should just be able to turn the belt 90 degrees, but no further, when the belt tension is correct.

[Softtail]

How do you mean, turn the belt 90 degrees? Do you twist it? Do you actually check the tension every 600 miles?? <<<<Softtail>>>>>

[BMT]

It's a one-time adjust 6,000 miles after installation on the 1150.

[BMT]

Only as a penance for fitting an after-market exhaust.

 

[ShovelStrokeEd]

Yeah, you twist it. It should turn 90 degrees right in the center between the pulleys. No, I do check it on the 12K service but adjust it, once, 5-800 miles after I install a new one. The belt on my 1100S went 49K miles without ever being touched after the 600 mile service only to fail with absolutely no warning. Rode about 40 miles to a hotel, then another 5 or 6 miles to a Pep Boys, got another belt and changed it in the parking lot. The old one was just a couple of strings wrapped around the crankshaft pulley.

[ESokoloff]

At 700 miles into the new belt, you should probably go back in there and, at least, recheck the tension. It is one of the steps in the 600 mile service and should be repeated 600 miles after the belt is changed.

 

 

Omission of this step COULD account for diminished belt life.

[BMT]

At 700 miles into the new belt, you should probably go back in there and, at least, recheck the tension. It is one of the steps in the 600 mile service and should be repeated 600 miles after the belt is changed.

 

 

Omission of this step COULD account for diminished belt life.

See my post above -- it is NOT part of the 600 mile service. BMW's schedule calls for a one-time check/retension at 6,000 miles after fitting.

 

Of course, it can be checked as often as an owner feels, just as he can change his oil every 3,000 miles, but it just might not be necessary.

[Ken H.]

Well just to fill in the blanks so to speak, were you adjusting the adjuster from the wrong side? It is adjusted from the front side, not from the back. The nut on the front of the ajuster bolt/stud is temporally replaced with a BMW jig piece (or a plain old acorn nut), then the correct torque is applied, held, and the other alt. retaining nuts are tightened to hold the alt. and belt in their proper place. Finally the retaining nut on the adjuster stud is reinstalled.

[Joe Frickin' Friday]

Well just to fill in the blanks so to speak, were you adjusting the adjuster from the wrong side? It is adjusted from the front side, not from the back. The nut on the front of the ajuster bolt/stud is temporally replaced with a BMW jig piece (or a plain old acorn nut), then the correct torque is applied, held, and the other alt. retaining nuts are tightened to hold the alt. and belt in their proper place. Finally the retaining nut on the adjuster stud is reinstalled.

 

For clarity's sake: you and the OP are talking about the 1150RT ('02 and later), but for anyone reading this who has an 1100RT ('01 and earlier), the adjuster is indeed worked from the rear side, using a hex bit socket and an unholy concoction of extensions and U-joints.

[Ken H.]

Yes, good catch. Indeed here we are taking about the 1150 series.

[Softtail]

OK, on my 20021150RT, there was a pot-metal allen nut with a gear on one end of the nut. This gadget was located on the back of the alternator and interfaced with a series of indentations machined/cast into the case. That is what I broke in half, the nut that is. My primary concern was that since this thing is now absent, could that cause the alternator to be mis-aligned. Everything tightened up OK without it, but I hate leaving out parts. <<<<<Softtail>>>

[ShovelStrokeEd]

You should be fine. The alignment of the alternator does not depend on the adjuster in any way. I believe there is a machined face on the front of the alternator that gets clamped against a mating face to hold everything in alignment. The adjuster bolt actually goes through the mounting flange and serves as one of the three clamping bolts but two should be more than adequate. The parts to fix this are not really expensive so you could pick them up via one of the mail order places such as Max BMW and replace next time you are in there. Tupperware and tank have to come off, but no really horrible deal.

[KMG_365]

I believe you're looking for #3 in the following diagram:

 

(linky)

 

For others: regarding the difference between the 1100's and the 1150's it apprears that the "idler" in the linked diagram changed after 11/03, but the screw itself is the same part number. I've used both the hex key from the rear and the BMW nut/spring from the front, but it doesn't seem to make a difference in belt life--too loose it slips, too tight the bearings in the alternator go out. Our alternators are still cranking out the juice without complaining (or making noise), but I'm thinking the sheaves might be getting worn down a bit. I thought I had more miles on my belt than I do, but I might get a chance to check Leslie's bike this Saturday and report on findings.