Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > alternator rotor retaining nut

[disco stu]

Originally posted by Shazaam!
Whoaa, slow down here. It's a '95 bike that has never had the nut removed.

1999-2000 Flywheel/Alternator Rotor Retaining Nut Problem

For the 1999 models, Ducati redesigned the electrical system, going from a 350 watt design to a 500 watt three-phase system. This resulted in a new flywheel retaining nut design that unfornunately also had an oversized thread depth that would loosen-up, even when properly torqued and Loctited.

Ducati issued a service bulletin concerning the stock nut. If the nut spins-on with little resistance it’s out of spec and must be replaced with an upgraded nut from Ducati. An different rotor was introduced for the 2001 model year that put an end to the issue.

Alternatively, Nichols Manufacturing offers a replacement self-locking double-nut similar to what Ducati used in the early ‘90’s.

Prior to 1999, the factory-installed nut did not commonly loosen, but they present a more serious problem if not properly torqued during (say) an aftermarket flywheel replacement. When they come loose, they’ll often damage the crankshaft splines. On pre-1999 models, you just need to replace/retighten the nut to the correct torque.


Symptoms

The first indication of a problem is a knocking noise from the left side of the engine that doesn’t go away when you pull-in the clutch lever. (The knocking noise sounds similar to the clutch knock at idle.) Excessive clutch tang wear and a broken clutch pushrod at the o-rings are also an indication. If you look into the timing inspection window on the left cover you can see if the flywheel is wobbling. Another apparent symptom is sluggish initial turnover when starting the engine because of interference caused by loose parts.

Solution

The solution is to replace the castellated nut and retorque. If the nut spins-on with little resistance it’s out of spec and must be replaced. Alternatively, Nichols Manufacturing offers a replacement double-nut (similar to what Ducati used in the early ‘90’s) that is self-locking.

http://www.www.nicholsmfg.com

Procedure

http://www.mad-ducati.com/Technical/...torCover2.html

Place a piece of soft metal (like a copper coin) between the starter pinion and the first idler gear to immobilize the shaft while you tighten the flywheel nut.

Best way is to actually make a tool to hold rotor. Some ingenious designs on this list, all other methods are inferior if you ask me. Course, the tool
takes some making, a fair machinest is required.

On engines with a solid countershaft drive gear (the gear behind the flywheel assy,) Ducati now recommends torquing the nut to 270Nm. On SP/SPS and other models where the countershaft drive gear is grooved where it sits on the crankshaft, you can only torque to 190Nm, to avoid damaging the gear.thanks shazaam,as i am sure no after aftermarket parts have been fitted it will be ok then,stu.



[Edited on 1-7-2005 by Shazaam!]

[TopiToo]

Originally posted by Shazaam!
Whoaa, slow down here. It's a '95 bike that has never had the nut removed.

1999-2000 Flywheel/Alternator Rotor Retaining Nut Problem
Ducati issued a service bulletin concerning the stock nut. If the nut spins-on with little resistance it’s out of spec and must be replaced with an upgraded nut from Ducati. An different rotor was introduced for the 2001 model year that put an end to the issue.

Hello

With reference I was introduced to the world of Ducati's 748's pre 2001 and after a year the lump seized due to the Alternator Rotor Retaining Nut doing its thing.

I missed the info/advise from Ducati at the time but bought a 2001 lump and all is well.

lesson learnt the hard way . . . I would not wish this on anybody, nice of Ducati turn their back once their warranty ran out.

[i]jpmercer

I then passed this information onto Ducati UK, and within 30 minutes they honoured the claim funnily enough, even wrote me a nice letter"

Is this the same company?



If the bike is pre 2001 I would have it checked.

regards

TopiToo

[moto748]

I think it's worth saying that I've been told by experienced Ducati mechanics that, notwithstanding Ducati service schedules and the Haynes manual, it's necessary to check the nut on late models with the 3-phase alternator as well. Better safe than sorry.

[Walenut]

So does anyone have any knowledge of the bolt coming undone on the earlier bikes, and is there a specific age of model that is affected by the crank plug backing out, or is that all models?

[Nattyboy]

I know early monsters and 888's especially were prone to the alternator nut coming loose...my mates came off his 888SP4 and shattered the casings..very expensive bill...I had the nut checked on my 888 checked as a part of my last service..

Cheers
Nat

[Shazaam!]

Flywheel Retaining Nut

In the early ‘90’s Ducati used two jam nuts to secure the flywheel, but replaced this design with a single very-fine-thread flange nut that carried with it an extremely high torque requirement.

There’s two parts to this issue.

First, the factory installed defective nuts on some 1999 and 2000 model year bikes before the loosening problem was caught. These nuts came loose even when installed with the correct torque because the treads were oversized. If you have one of these bikes, you should have it checked. If the nut spins on/off easily it should be replaced, not just re-torqued.

Second, the flywheel retaining nut design needs to be tightened to a very high torque level to keep it from loosening. It’s the highest-torqued fastener on the bike.

You’ll not get a loosening problem unless you’ve removed the nut for some reason. When you go to reinstall it you’ll find that without the proper tools it’s VERY difficult to immobilize the crank (which is necessary to reach the high torque) and many shops/owners don’t understand how critical this is. The use of this kind of nut in this particular application is on the envelope of fastener design.

So I’m not offering any advice here as to how to do it.

Consequently, some owners have decided to replace the single Ducati nut with the two jam nut design offered by Nichols.

http://www.nicholsmfg.com/

A couple adventurous owners have tried Nord-Lock washers with the stock nut.

http://www.nord-lock.com/default.asp?id=3&language=4

The point I’m trying to make is that if you don’t have a 1999 or 2000 MY bike. and you haven’t touched the flywheel nut, don’t worry about it coming loose.


To S.P.:

Crankshaft Oil Galley Plug

Early-year bikes had problems with this plug backing-out. If not caught in time, the plug would come out and you'd get a catastrophic loss of lubrication. In 2000, the aluminum oil galley plug was replaced with a steel plug, which solved the problem.

[Walenut]

Thanks Shazaam, interesting stuff. So with my 96-7 bike I won't worry about the alternator just the crank self destructing!

By the way is it warm and sunny over there?

[Walenut]

You know I’ve been thinking about the crank plug backing out and can’t understand why this would happen, is it the material used? I mean we are not talking about state of the art technology here crank plugs have been used in cranks for as long as cranks have had an end feed for the big ends, and it cant be the vibration that causes it because you can't get much more vibration than in a British parallel twin, so it must be a design fault and a pretty basic one really. On a British twin it is a steel plug that is staked in, and I’ve never heard of one these backing out.

Any one care to put me right on my theory?

[Shazaam!]

Since aluminum expands about three to one vs. steel, my thought is that the softer aluminum threads deforms locally from repeated differential thermal expansion and eventually loosen-up the threaded fit. Ducati's 2001 switch to a steel plug was enough to solve the problem.

[Edited on 1-10-2005 by Shazaam!]

[Walenut]

I wonder why they decided to go with aluminium?