Belt tensioning - Ducati.ms

heffergm · Jun 19th, 2009, 6:19 am

I've got another belt tensioning question....:

Can someone confirm for me where they're plucking the belt? Because obviously location is going to determine the frequency to a large extent since the tension isn't uniform.

My belt is a lot tighter on the top run than the bottom. I'd be lucky to get a 2mm allen between the belt and the adjuster on the top run. Measuring by the twist method though (just to the right of the top adjuster) I get roughly 45 degrees of twist, so I don't think it's that far off.

dhc8guru · Jun 19th, 2009, 9:50 am

The belt should be slack on the tensioner side and tight on the opposite side.
If you get the slack on the sliding tensioner side, set your microphone up along the slack side in the middle distance between the tensioner roller and the gear on the short run side. I placed the mic under the belt which gave good results. I just thrummed near the microphone. I tried different distances from the mic, but I got the same reading. I set the belts to 95hz. I think the latest recommendation is 90-100Hz ±5 Hz for used belts. Although this tolerance range makes no sense since they give a deviation and a limit tolerance. I figured it was best to just use 95Hz.
The hardest part was finding a decent piece of software for testing the Hz freq. Every suggested software was either way to complicated or completely wrong. I ended up finding a simple software that just shot out what the Hz frequency was. I don't remember the name of the software, its on my other computer. When I get a chance I will post it so other people can download it.

heffergm · Jun 19th, 2009, 10:11 am

How about "top" or "bottom" rather than "side", which just confuses me more :lol:

So I gather the bottom roller is the adjuster, and this is where the slack should be and where I should take the reading?

dhc8guru · Jun 19th, 2009, 12:49 pm

top, bottom, side to side? I guess it depends on which belt your tensioning?

You know I can't remember which roller is the adjustable one on the horizontal cylinder I believe it is the lower one. I remember on the vertical cylinder it is the one on the right.

If I recall correctly, Ducati spells out to rotate the engine around 270° going from the horiz. cyl and vert. cyl. to set the tension and then do it a second time to verify the tension retains to spec.

I found the link for the software I liked.

http://enableencore.com/guitartuner.htm

heffergm · Jun 19th, 2009, 8:29 pm

Ok, so:

In the picture above, I plucked the horizontal belt between the bottom roller (the adjustable one) and the forward cam (forward meaning the one closest to the front of the bike, to the right side of the pic). First question: is this the correct place to pluck?

I analyzed the waveforms I got from several plucks, ala this post:

http://ducatimonsterforum.org/index....6523#msg196523

Essentially, I found that peak indicated in each waveform I got was around 46hz, which would make my belts way too loose. Just trying to verify I'm doing this correctly before I actually muck with anything. The bike has 1000 miles on it now (08 leftover) so I'm expecting they did stretch a bit. If I twist the belt in the same place I plucked to measure the tension, I can get way past 45 degrees, but I'm unclear if this is the correct location to get a general idea if I'm in the ballpark with the twist method.

heffergm · Jun 23rd, 2009, 1:28 pm

Quote:

Originally Posted by heffergm

Ok, so:

In the picture above, I plucked the horizontal belt between the bottom roller (the adjustable one) and the forward cam (forward meaning the one closest to the front of the bike, to the right side of the pic). First question: is this the correct place to pluck?

I analyzed the waveforms I got from several plucks, ala this post:

http://ducatimonsterforum.org/index....6523#msg196523

Essentially, I found that peak indicated in each waveform I got was around 46hz, which would make my belts way too loose. Just trying to verify I'm doing this correctly before I actually muck with anything. The bike has 1000 miles on it now (08 leftover) so I'm expecting they did stretch a bit. If I twist the belt in the same place I plucked to measure the tension, I can get way past 45 degrees, but I'm unclear if this is the correct location to get a general idea if I'm in the ballpark with the twist method.

FWIW, I brought the bike in for its first service. After getting it home and checking the belts, I get repeatable numbers using the same technique of 68-70Hz, so it would appear my dealer did retension the belts as they'd said they would if required, and they work on the loose end of the scale at ~70hz. There's a very audible difference between the 46hz I was getting before and 70hz.

ORIF · Jun 23rd, 2009, 3:43 pm

So is the 5mm allen wrench method no longer acceptable?

I actually have the old Ducati belt tensioning tool but no idea as to how to use it.

I guess I am a Luddite.

heffergm · Jun 23rd, 2009, 4:31 pm

In a word, no. Use that method on a newer 2v and you're way too loose.

Quote:

Originally Posted by ORIF

So is the 5mm allen wrench method no longer acceptable?

I actually have the old Ducati belt tensioning tool but no idea as to how to use it.

I guess I am a Luddite.

Jeff4510 · Aug 4th, 2009, 4:17 pm

Quote:

Originally Posted by dhc8guru

top, bottom, side to side? I guess it depends on which belt your tensioning?

You know I can't remember which roller is the adjustable one on the horizontal cylinder I believe it is the lower one. I remember on the vertical cylinder it is the one on the right.

If I recall correctly, Ducati spells out to rotate the engine around 270° going from the horiz. cyl and vert. cyl. to set the tension and then do it a second time to verify the tension retains to spec.

I found the link for the software I liked.

http://enableencore.com/guitartuner.htm

just adjusted these and they were both at aout 45hz and I could turn them almost 90 degrees. I set them both to about 90-100 depending where the bike stopped at when I rotated it. The one thing I don't understand is holding the cam. I cannot wrap my head around how holding it in place will havev any affect on the timing as the belt will center itself the second it starts to spin, right? I do understand that by tightening and loosening it you are adjusting the cam timingbut this cannot be helped ultimately?