Ducati Monster Forum

Moto Board => Tech => Topic started by: Privateer on December 28, 2018, 03:49:23 PM

Title: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 28, 2018, 03:49:23 PM
apparently my chain tension adjuster came loose and mangled the swingarm.

(https://i.imgur.com/BRKyW5P.jpg)

I've ordered new bolts, but any suggestions on how to bend the box section back?
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: ducpainter on December 28, 2018, 03:54:43 PM
Steel, or aluminum?
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Dirty Duc on December 28, 2018, 03:57:06 PM
Careful tapping with a hammer.

It's likely never going to be perfect, but IMO isn't very structural back there.

Of bigger concern is the root cause. I think you should check torque on the axle nuts.

And I think you are missing the piece that keeps that bolt in the sliding piece.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Speeddog on December 28, 2018, 05:18:48 PM
Modest sized adjustable wrench works well.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 28, 2018, 08:11:47 PM
Quote from: Speeddog on December 28, 2018, 05:18:48 PM
Modest sized adjustable wrench works well.

clamp on and bend?


Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Dirty Duc on December 28, 2018, 08:15:37 PM
Yes. Same caveat as above, and don't try to fix it all at once.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 29, 2018, 05:45:13 PM
Quote from: Speeddog on December 28, 2018, 05:18:48 PM
Modest sized adjustable wrench works well.

spot on, as always. sometimes had to use two wrenches to hold one section while bending another.

(https://i.imgur.com/SMfj3YY.jpg)
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Howie on December 29, 2018, 09:50:38 PM
 [thumbsup]
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Dirty Duc on December 29, 2018, 09:52:26 PM
Well done!
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 30, 2018, 11:24:12 AM
at this point I'm wondering when it happened and how long I rode on it like that.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: greenmonster on December 31, 2018, 04:05:16 AM
Were wheel nuts torqued properly?
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Speeddog on December 31, 2018, 07:32:43 AM
Quote from: Privateer on December 30, 2018, 11:24:12 AM
at this point I'm wondering when it happened and how long I rode on it like that.

Not long at all.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Howie on December 31, 2018, 07:45:19 AM
Usually because after a wheel R&R the adjusters were not tightened enough.  Or the axle not sufficiently torqued, as greenmonster said.  I your case?  :-\  Since there appears to be no damage in the sprocket area I have no idea why things got so mangled.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 31, 2018, 02:20:21 PM
Quote from: greenmonster on December 31, 2018, 04:05:16 AM
Were wheel nuts torqued properly?

52 ft lbs
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: ducpainter on December 31, 2018, 03:43:09 PM
Quote from: Privateer on December 31, 2018, 02:20:21 PM
52 ft lbs
You need to be a bit higher... http://www.ducatimonsterforum.org/index.php?topic=50011.msg915911#msg915911
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 31, 2018, 05:49:59 PM
Quote from: ducpainter on December 31, 2018, 03:43:09 PM
You need to be a bit higher... http://www.ducatimonsterforum.org/index.php?topic=50011.msg915911#msg915911

Quote from: Ddan on May 06, 2008, 01:46:27 PM
Some torque values, taken from the Haynes 2valve, '91 to '96, and LT Snyders, Vol. 1

Rear axle nut                                70-76 Nm

Rear wheel axle nut                        69-74 Nm


not sure which of those numbers is right, but  I double checked my LT Snyder book and it says 70 nm/51.6 ftlbs.

are these not right? 

I can fix it of course, but I want to make sure I'm using the right resource.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: ducpainter on December 31, 2018, 05:59:47 PM
Isn't your bike newer?

I believe it uses a different size axle than the bikes the Haynes and LT's numbers are referencing, and requires more.

howie is pretty good with his info. Maybe Nick can confirm.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on December 31, 2018, 06:10:13 PM
Quote from: ducpainter on December 31, 2018, 05:59:47 PM
Isn't your bike newer?

04 620
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: ducpainter on December 31, 2018, 06:33:56 PM
I'm pretty sure it uses a larger rear axle.

Your bike's frame is for all intents and purposes the same as a 695.

Here's a scan of a shop manual... http://kuixihe.com/Downloads/How%20to%20repair%20and%20maintain%20Ducati%20695.pdf

It says 83 lbs/ftNm.

I'm assuming your bike has a 25mm rear axle.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Howie on December 31, 2018, 08:21:49 PM
Yep, 83Nm. 
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Speeddog on January 01, 2019, 07:48:33 AM
I've seen when the axle's ~loose, it can load up that tensioner bolt and break it.
In that case, the cap escapes completely.
And it's then even more obvious as the axle is unrestrained and slips position.

If the tensioner bolt isn't *quite* tight enough, it loosens due to the rather aggressive vibration, and then the cap self-employs, like this case.

Yes, 25mm axle is 83 N-m (63 ft-lb)
Tensioner bolts (chain adjuster screw) 8 N-m (6 ft-lb)

There's a small bolt that goes in the inner end of the tensioner bolt, keeps it from unscrewing completely from the axle slider block.
That bolt head has broken off, so it may be still sitting inside there.
Best to retrieve it so it doesn't jam the slider block at a later date.


Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Privateer on January 01, 2019, 04:45:42 PM
thank you all.  updated my Desmo Times shop book.
Title: Re: mangled swingarm/chain adjuster - fix?
Post by: Qomomoko on January 08, 2019, 12:35:06 AM
Interesting and unfortunate story.
I was under the impression that chain "adjuster screws" were more stable/solid.
I better go play with mine and make sure all the parts are SAT, especially the retaining screw for the sliding shoe.