Ducati Monster Forum

Moto Board => Tech => Topic started by: dogcatcher on October 05, 2008, 09:31:35 PM

Title: Front sprocket nut backed off at 630 mi.
Post by: dogcatcher on October 05, 2008, 09:31:35 PM
I just wanted to post this as a word of caution for fellow Ducati owners.  This evening, I was cleaning my chain on my S4RS and decided to take off the front sprocket cover in order to do a thorough job.  To my horror, I discovered that the large safety washer was FLAT and the front sprocket retaining nut was spinning freely.  Luckily, the damn thing stayed on while I was riding.  I have to re-install the nut to 186 nm and fold the safety washer over the nut, right?  What size socket do I need?

BTW, I checked my 848 (also new) and the washer was folded with paint on it.  I guess someone at Ducati missed the one on the Monster.

Oh well, it could have been worse.

D
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: hypurone on October 06, 2008, 07:14:42 AM
That was the case with the LH rear nut on mine! Luckily the retaining clip held it on.  >:( So much for quality control.
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: dogcatcher on October 07, 2008, 03:58:56 PM
Well, I took it back to Bert's and the techs all looked puzzled.  I guess their Ducati tech was out of the office.


In the end, my service writer said that they put loc-tite on it and torqued it to 50ft/lbs.  They said that the S4RS does not use lock-washers on the front sproket.

I read somewhere that it should be torqued to 180 some odd Nm and then have the large washer folded over the nut . 

Who is right?
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Jethro on October 07, 2008, 04:44:12 PM
You can download the Parts List from Ducati.com  HERE (http://www.ducati.com/en/bikes/service/parts/2008.jhtml?family=parts) and it looks like for S4RS the Nut is Part No 750.1.007 and the Lockwasher is Part No 851.1.004
These are exactly the same parts as on my M1000s and I've just fitted new sprockets and chain  -  for my bike the front sprocket nut is definitely 186Nm with Moly grease not Loctite.
I think you should have another look at that.
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Howie on October 07, 2008, 10:20:54 PM
You might want to show this to your dealer, it is from the shop manual.

Front sprocket retaining nut   M25x1.5    186 *    GREASE B
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Capo on October 07, 2008, 10:35:09 PM
You might also want to consder finding a new shop  ;D
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: dogcatcher on October 07, 2008, 11:15:41 PM
Taking it to Pro Italia tomorrow for some proper maintenance
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Speeddog on October 07, 2008, 11:19:24 PM
Well, they should easily be able to do better than Bert's.
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: DucHead on October 08, 2008, 03:57:01 AM
You could probably buy a torque wrench and some assembly grease for less than a service call.
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: hypurone on October 08, 2008, 05:54:48 AM
Quote from: dogcatcher on October 07, 2008, 03:58:56 PM
Well, I took it back to Bert's and the techs all looked puzzled.  I guess their Ducati tech was out of the office.


In the end, my service writer said that they put loc-tite on it and torqued it to 50ft/lbs.  They said that the S4RS does not use lock-washers on the front sproket.

I read somewhere that it should be torqued to 180 some odd Nm and then have the large washer folded over the nut . 

Who is right?

Yikes! Time for a new service dept! Def torque that sucker to 137 ft lbs AND bend the washer over one of the flats on the nut. If you're near me (Sonoma) cmon over, I'll do it for ya.  [thumbsup]
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: dogcatcher on October 08, 2008, 09:21:43 PM
Took pompetta's advice and bought sockets and a torque wrench today and fixed that pregnant dog myself.  I even turned the Maint. light off.

Damn I'm good!

Thanks for the help everyone.

D
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Jethro on October 09, 2008, 02:10:15 AM
Good to hear you've fixed it yourself and you needed a torque wrench to do a lot of maintenance anyway. Just one thing though - I hope you cleaned the old Loctite off the thread and fitted the nut with moly grease? (Ducati specify Grease 'B' in the manual for this nut which is moly grease)
The clamping load that you want to achieve by using a torque wrench depends on the friction in the thread and under the bolt head; with about 40% being used to overcome thread friction and about 50% used to overcome underhead friction - leavintg only about 10% to produce bolt tension and hence the desired clamping load. If you still had the old Loctite on the thread the friction would be a lot higher so desired clamping load would be a lot less.
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: dogcatcher on October 09, 2008, 06:47:40 PM
When I spun the nut off, I didn't see any evidence of Loc-Tite on the shaft.....just some black grease.  And the nut spun off freely so I didn't see the need to clean the threads.  I'll do the whole thing over soon anyway when I add the 14t sprocket.

Thanks for posting.

D
Title: Re: Front sprocket nut backed off at 630 mi.
Post by: Jethro on October 10, 2008, 12:35:01 AM
If the nut spun freely and there was black grease that sounds fine - the black grease was probably the original moly grease which 'Bert's' didn't remove. It looks like 'Bert's' workshop does not know how to use Loctite properly, which in this case was a good thing.  [laugh]
Sounds like you did a good job.