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Tightening the alternator belt on a RT-P, from the front side only?


Nevets

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OK, so I have a 2003 RT-P, with (I strongly suspect) a slightly loose alternator belt. I won’t go into all of the details, but it appears that a slipping belt is possibly causing the voltage to droop a little when I have all lights on or the heated grips, etc. I had posted about this voltage droop problem before, and have checked electrical connections as suggested, and have not found anything in that direction. Made it to Torrey and back without much problem, but I think the problem is getting worse lately.

 

I managed to get the alternator belt cover off partway so I could do the 2-finger belt twist test, and as far as I can tell it’s a little loose. Since It’s a RT-P with the extra supports in there, space is at a premium. It looks like I might be able to slice the plastic cover in half while it is slipped a little lower with a dremel/saw blade. Worse comes to worse, I can replace that “hacked with a dremel” cover with a new cleanly cut cover later…

 

Anyway, I see the three bolts and know that the top and left (while viewed from the front) are normally loosened and the right one is used to torque the alternator upward, using special tool, etc (per BMW manual). Basically my question is, can this loosening, tightning, etc be done without access to the back side on the alternator? Do I need to disassemble the bike, taking the tank off to access the nuts on the back side of the alternator? Or can I do it all from accessing the three bolts/nuts on the pulley side?

 

Any help is appreciated. Don’t want to do a complete tear down if I can avoid it…

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ShovelStrokeEd

No problem so long as the position of your cut allows you to insert a small pry bar under the alternator body. Loosen all three fasteners, pry up on the alternator till belt tension is correct and then tighten one. Recheck tension and if still OK, tighten the other two. I could never understand why BMW made such a big deal out of this. Great idea using a little gear train to allow tightening of the alternator. Stupid idea to require tank removal to access the adjuster.

 

BTW, one of those little 6" tire spoons that used to come in a BMW tool kit when tires had tubes and is still available from Motion Pro is the nearly perfect tool for the job.

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I could never understand why BMW made such a big deal out of this. Great idea using a little gear train to allow tightening of the alternator. Stupid idea to require tank removal to access the adjuster.

 

Ain't that the truth. I had mine all apart on Saturday......I must have stared at it for 10-15 minutes trying to figure out how to get to the adjuster without moving the tank WAY out of the way. I ended up doing like you said and just shoving a big flat head screw driver under the alternator and prying up on it. Great idea.....poor execution.

 

I can only imagine the discussions that were going on between the marketing people and the engineers during that meeting. lmao.gif

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I could never understand why BMW made such a big deal out of this. Great idea using a little gear train to allow tightening of the alternator. Stupid idea to require tank removal to access the adjuster.

???

 

Remove the cover, loose the two bolts, and remove the nut on the stud that is attached to the ratching mechinism on the back side. Replace the nut with the BMW tool or any old acorn nut that will fit. Turn the tool/nut clockwise, thus ratching the alternator upward. Then while holding it in place with tension on the tool/nut, tighten one of the bolts. Now you can release the tension, tighten the other bolt and put the original nut back on the stud.

 

When finished polish your still in place fuel tank.

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Remove the cover, loose the two bolts, and remove the nut on the stud that is attached to the ratching mechinism on the back side. Replace the nut with the BMW tool or any old acorn nut that will fit. Turn the tool/nut clockwise, thus ratching the alternator upward. Then while holding it in place with tension on the tool/nut, tighten one of the bolts. Now you can release the tension, tighten the other bolt and put the original nut back on the stud.

 

When finished polish your still in place fuel tank.

 

And thats why we have an internet forum. So guys like Ken can come along and make me want to beat my head against a wall for missing something as easy as that. dopeslap.gif

 

In my defense, I didn't know BMW had a special tool for that, but that is certainly much easier than trying to get a wrench on the back side of that adjuster.

 

Actually, I guess if you were in a pinch you could remove one of the other alternator nuts, double them up on the adjuster bolt, tighten them together, and do it that way also. I learned something today clap.gif.

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You mean to indicate that it is a bottoming nut that causes the unit to rotate? Oh, the pain of it all. I think I'm going down to the BMW dealer and demand my $100 back for the labor charge they gave me.

Then I'm going to hide my head in shame and blab it all over the internet.

Sheesh dopeslap.gif

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The BMW "Special Tool" for this job is 12 3 551. IMO, well worth the price and it's small enough to carry in your toolkit.

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OK, finally getting to it.. Dang if I'm not missing a 13mm box/open end wrench to use on the top bolt. Need to get some more horsepower to loosen the left bolt also, since apparently it was made tight via gorilla. Stay tuned, got to go buy tools! Yahoo!

 

Wait, I forgot to ask.....It sounds like there is no reason this can't all be done from the front, without taking off the side tupperware, right?

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Alright….finished the belt tightening, at least for tonight. Tried to use Ken’s technique, but believe it or not, I didn’t have a 8mm 1.25 acorn nut or equivalent. Tried to use a conventional 8mm nut with bolt partially inserted, and ALMOST messed up the threads on the pivot bolt. Yikes! Could see how this works, and a torque wrench would allow for a measureable tightness (8Nm?), but have to have a better full-thread closed nut to try that again.

 

Anyway, used a big honkin’ flat-blade screwdriver to lift the alternator, and the belt seemed to get it a little tighter after snugging down the bolts. Tighter, but not sure if tight enough….

 

Because when I went for a test drive, the symptom of low voltage (fast flashing turn signals) persisted. No I don’t have bulbs out, and yes the bulb socket connections are fine. Either the alternator belts not the problem, or its not tight enough. I did seem to notice a fair amount of black gunk come off on my fingers while checking the belt for tightness. Kind of makes me wonder if the gunk is made of belt particles (from slipping?) that are now acting to make it slip more.

 

I do have a new belt, but that will have to wait until I can get the plastic cover cut and off.

 

In other words………to be continued!

 

Thanks for all your help.

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The BMW "Special Tool" for this job is 12 3 551. IMO, well worth the price and it's small enough to carry in your toolkit.
Looks like this:

 

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What do you suppose the funtion of the spring is? confused.gif

Other than that, looks like hex stock with a 8mm tapped hole in it...

 

What is the price anyway? I though this was something like $100?!? eek.gif Nevermind, I just saw the $25 on the photograph....

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What do you suppose the funtion of the spring is? confused.gif

 

Other than that, looks like hex stock with a 8mm tapped hole in it...

I think it's to help keep the stud engaged in the adjustment cam behind the alternator mounting plate.
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Ahhhh.....maybe that explains why the "ratcheting" you mentioned did't seem to be occuring. OK, so may the spring would be helpful.

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Jim VonBaden

IMHO the tool is a waste of money, and harder to use than Ed's method. The only addition I would make is to ensure you don't pinch the HES wires on top of the motor between it and the alternator. Twist the belt 90° and if it is tight at 90° you have it tight enough.

 

No need for a $40 nut to do it. dopeslap.gif

 

Jim cool.gif

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Preach it, Jimmy!

 

BTW, I think you have some other problem besides a loose belt. A loose belt will chirp and squeal, but I've never heard of one causing inadequate charging.

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Preach it, Jimmy!

 

BTW, I think you have some other problem besides a loose belt. A loose belt will chirp and squeal, but I've never heard of one causing inadequate charging.

 

I'm afraid you may be right about it being something else besides belt tension. I think I'll put a new belt on anyway, just to reassure myself that it's not slipping, and I know how to do it....

 

As far as the cost of the BMW adjustment tool (I may be missing something here), but isn't it a good way to get a "calibrated" belt tension, since a torque wrench is used on the tool in the BMW instructions? Besides, does BMW really care what we think about the cost of a tool, probably intended for dealer use?

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