Alternator Belt Tension

[Hit Man]

G11, 6,000 miles

I know nobody has/uses the Moto Guzzi specified alternator belt tension tool, and the 90 degree belt twist method has been referenced here. Checked my belt tension for the first time. Yeah, with moderate tesion, I can twist it 90 degrees. With more force, I go go a little beyond 90 degrees: Adequate, or worth tightening?

The problem I have with methods like these is how hard should I be trying to deflect the belt. Can anyone compare to a simple belt deflection in the middle of the span ( a method I'm a little more used to)? I can get a little more than 1/4" of deflection.

 

[Penis Rotor]

It's not slipping? It's fine!

I have the tool. Problem is that the factory doesn't give you a torque to use.

Better to be a little loose than too tight. Too tight and you have the potential to dmage the alternator bearings and even, if much too tight, the front main.

Pete

 

[Hit Man]

Thanks Pete,

I don't think it's slipping; didn't see any rubber dust in the housing. I'm also against too much tension, but wasn't sure how sensitive this design was without any sort of idler pulley or more of a wrap around the pulley.

For some reason, part of the edge of the belt has some cord exposed. It's not all the way around the belt - don't think this is related or significant (?).

 

[Phang]

I bought the tool before I got my G8V, it is collecting dust in my tool box until I figure out the torque to use it. The manual says 50Nm for belt tension, I am going to try that when my belt is due for replacement.

 

[john zibell]

That torque specification looks excessive to me, and probably a misprint. A similar procedure is used on BMW oil heads and the torque applied to the alternator is only 8 Nm. I think the alternator belt and valve cover screws are best tightened by feel. Using torque wrenches for these items may cause problems. Besides,it just needs to e tight enought for the belt not to slip, which isn't very tight.

 

[Phang]

Hi John, 50Nm seems excessive to me too. I will start with lower torque settings with the tool and see how it goes.

In BMW oil head example, the 8Nm torque is acting directly to the base of the alternator via an adjuster resembling a rack/pinion to jack up the alternator.

Guzzi’s belt tensioning tool is lifting the alternator via an arm pivoting at the alternator support plate. That will require a greater torque in my opinion but probably not as much as 50Nm.

Don’t get me wrong, I am fully agree with what you’ve said half a year ago - “a little wrench art goes a long way”. Some suspiciously high and inconsistent torque settings in Guzzi manual has made me think twice before I reach for my torque wrench :lol:

Phang

 

[Greyo]

I bought the tool before I got my G8V, it is collecting dust in my tool box until I figure out the torque to use it. The manual says 50Nm for belt tension, I am going to try that when my belt is due for replacement.

Any update on what is the correct torque for setting the alternator belt tension, using the freakin' Guzzi tool?

 

[Phang]

Not from me as my bike has only clocked 13,000km (8125 miles) till date. Until it hits 50,000km (31,250 miles), the belt tensioning tool remains as a handy paperweight.

Phang

 

[Greyo]

... my bike has only clocked 13,000km (8125 miles) till date. Until it hits 50,000km (31,250 miles), the belt tensioning tool remains as a handy paperweight...

Actually, concerning the time/mileage intervals recommended for checking the alternator belt tension, we have here another prime example of how confusing and potentially misleading Guzzi shop manuals can be; under "Every 20,000 km (12,500 mi) or 24 months" the manual says "Alternator belt - Adjust", which is immediately followed by a cryptic "EVERY 50,000 Km (31,050 mi)". So, what is the CORRECT interval for checking the belt tension? 20,000 or 50,000 km? To me waiting 50,000 km seems too much for the first check; it makes more sense to have a check every 20,000 km and REPLACE the belt with a new one every 50,000 km... what do you guys think?

 

[john zibell]

To me waiting 50,000 km seems too much for the first check; it makes more sense to have a check every 20,000 km and REPLACE the belt with a new one every 50,000 km... what do you guys think?

Personally I'm not so anal on the alternator belt. They aren't under much stress. I've been working with them on BMWs for some time and their spec is to change them every 36 thousand miles. Yet I've worked on bikes with twice that mileage and they have not had a belt failure. In my opinion, look at them once and awhile. If there is no cracking of the belt material run it. I would believe they would fail from rot before they failed from mileage.

 

[schimenator]

Obviously I've never had mine apart, but could you use some kind of force gauge? You know 10 pounds equals 1 inch of movement or something along those lines. Maybe use an old fish scale?

 

[john zibell]

Obviously I've never had mine apart, but could you use some kind of force gauge? You know 10 pounds equals 1 inch of movement or something along those lines. Maybe use an old fish scale?

I think you are trying to make it too complicated. Just go with the 90 degree twist thing. So long as it is tight enough to turn the alternator without slippage (you would hear that) it is just fine. The danger is to get it too tight where it may cause bearing damage.

 

[Greyo]

I think you are trying to make it too complicated. Just go with the 90 degree twist thing. So long as it is tight enough to turn the alternator without slippage (you would hear that) it is just fine. The danger is to get it too tight where it may cause bearing damage.

Could someone provide more details on how the 90-degree procedure is done?
I hope this is not a repeat; I did a search on it, but with no results.
Thanks.

 

[john zibell]

At a mid point of the belt, see if you can twist the belt 90 degrees. If about 90, it is good, if much more it is loose, if less than 90, it is too tight.