Nichols flywheel failure

[lowd239]

Ive been having some issues starting my 2001 M900Sie over the past couple months and today decided to take the starter sprag out to do the spring modification -http://www.mad-ducati.com/Technical/StarterSpragClutch/SpragClutch.html


When I got the flywheel off I noticed some aluminum shavings and saw that the aluminum splines on the Nichols flywheel had sheared off!  That explained the starting issues, but I did some searching and it doesnt sound like there have been any issues with the aluminum Nichols flywheels failing.  As you can see from the photos, its not pretty.

Nichols website is suspended so Im not sure if they are still in business.  Anyone know?  Id like to contact them about the flywheel.  Most likely Ill just look for a stock steel flywheel, so if anyone has one laying around feel free to message me.

Thanks!
Jeff

[ducpainter]

You're not the first to have an issue with an all aluminum flywheel.

Nichols is still there AFAIK.

It might just be a tech glitch with the site.

I'm sure someone here has contact info.

[muskrat]

ouch!

I have one but it's for a 996 engine.  Not sure it will work but if it does you can pay shipping and it's yours.

[TAftonomos]

I've heard of this, but never actually seen it.

Guesses to the cause?

[junior varsity]

I've only heard of this with respect to the aluminum DP flywheels but never seen it posted - not heard of it happening to a Nichols flywheel ever.   Surprising for sure. 

It looks like their website may be down but I doubt the business is down - you can find their phone stuff by googling Nichols MFG

[booger]

The only way I could see it happening is if somehow the nut backed off and allowed a little bit of slop to present itself at the shaft, and the tolerance grew larger over time until catastrophic failure. Aluminum vs. steel.

Was the nut tight when you removed it? Was it a Nichols flywheel nut do you suppose? And isn't there supposed to be two nuts on that shaft, one tension nut and one jamb nut?

[junior varsity]

I've heard numerous recommendations as to quintuple checking the torque on the flywheel nuts - not sure if it was for this exact reason or another - but also that the single nut be swapped out for the double jambnuts - I actually got the pair of jamb nuts from Nichols for the OEM flywheel on the M900 motor that's getting overhauled in the garage as a precaution.

[ducpainter]

The only way I could see it happening is if somehow the nut backed off and allowed a little bit of slop to present itself at the shaft, and the tolerance grew larger over time until catastrophic failure. Aluminum vs. steel.

Was the nut tight when you removed it? Was it a Nichols flywheel nut do you suppose? And isn't there supposed to be two nuts on that shaft, one tension nut and one jamb nut?

The Nichols set up is two nuts.

[TAftonomos]

Even the cheapy ebay flywheels come with 2 nuts. 

I've used about 4 of those, and never had an issue (the cheapy ebay ones).

Ughh...

[ducpainter]

Factory is a single...no?

[TAftonomos]

Yup.  It has quite a lot of engagement on the threads (nearly 1" thick iirc).  Pretty sure it's a case of not being torqued correctly that caused the failures. 

With a double nut AND loctite...I don't see how it could inadvertently back out.

[ducpainter]

Yup.  It has quite a lot of engagement on the threads (nearly 1" thick iirc).  Pretty sure it's a case of not being torqued correctly that caused the failures. 

With a double nut AND loctite...I don't see how it could inadvertently back out.

Agreed.

I don't think they loosen.

I think the heat cycling causes the nuts to push into the aluminum which increases the gap between the nuts and aluminum surface. Once that happens the splines 'fret' and wear out.

[junior varsity]

there there, don't fret

[ducpainter]

there there, don't fret

No numinum flywheel for this kid.

[lowd239]

Thanks for the offer muskrat, you have a pm!

As for the nut backing off...that was certainly not the case, I had a heck of a time loosening it.  And there wasnt any horizontal play in the flywheel with respect to the shaft.  

Oddly enough, the bike would actually start under the current flywheel's condition.  I would only get one shot to start the bike and if the motor stumbled and died the starter motor would free wheel.  Once started though, the starter motor would engage after shut down.  

From the way it failed, it looks as if the splines were sheared from a torsional stress which seemingly would only come from the starter motors torque.  Perhaps there was some kick back from the engine on the starter motor which caused the shearing.