Engine rattle, counter balance nut washer?

[Flynn]

Just riding my 610 without ear plugs I've noticed an engine rattle at certain RPMs.

I'm thinking that it is the counter balance nut washer.

For some reason the washer is loose behind the nut even though the nut has been torqued to the correct 70NM.

It's either that or the cam chain bedding in and needing more tension as it goes through the initial loosening stage.

But that washer is annoying me, purely because I can't see how it is able to turn when the nut has been torqued down correctly.

Perhaps the thread on the nut isn't long enough for the nut to put pressure on the washer?

 

[HuskyBrutha]

Dont take a chance on that nut, I would get that wash sorted quick quick. Dont leave it.
There have been a number of documented cases on the www where the nut either comes loose, despite having one side of the washer turned up against the nut or a piece of the washer piece breaks off, the net result being expensive engine damage.
Apparently the vibrations and harmonic conditions within these motors are such that nut likes to work itself loose and also the stock washers dont survive all that well.

Here is a nicely doumented altertative washer sollution:

View: https://www.youtube.com/watch?v=IKwWu2w1gGk

 

[Rotax_655]

You can fix it with Loctite 648

 

[Flynn]

Rotax_655 I've already used red threadlock. Not Locktite, an equivalent. Just as good as Locktite, but it's not something I want to rely on.

When I pulled the starter flange,

I noticed the washer was loose, removed the nut and washer, replaced the washer, retorqued the nut to 70nm and noticed that the washer was still loose. So it seems like the nut doesn't clamp the washer at all.

But the nut itself was never loose before or after.

I don't even know which way up the tang of the OEM washer is supposed to go. I just put it in the woodruff key slot since that was the only obvious place for it.

Just checked the manual, it says to

insert a new safety washer with tab in correspondence of the key

I've got no idea what they mean by that!

Also, it says to torque the nut to 7.1 NM, is that a misprint!? That's hardly anything!

Check this attachment

The table says M18 for the CB shaft, I'll get Nordlock washers ordered asap, assuming that they will do the job and won't have any downsides

These are what I'm going for

http://www.ebay.co.uk/itm/M3-to-M20...hash=item2f0932b31b:m:mKAtnltNzaVqAiLHLcrKULw

Can only order 10 at a time though! £20 and I'm only using one pair!

 

[Flynn]

Sorry attachment didn't post

 

[BiG DoM]

I torqued mine to 100Nm (may have been the other one to yours) and also Loktited it with heat resistant thread lock. I am also puzzled how they can come loose as not only is there a locating tang on the rear of the washer washer but also it gets lipped up ??? Yes if not torqued from the factory but thereafter? I painted mine so can se it through the oil filler.

 

[BiG DoM]

Yes the 7.1Nm is a misprint - obviously came about with the metric conversion … and too much vino at lunch.

 

[Rotax_655]

Rotax_655 I've already used red threadlock. Not Locktite, an equivalent. Just as good as Locktite, but it's not something I want to rely on.

Not a product anymore
This "Loctite 648" is exceptional

It is best to lock the high temperature nuts with engine oil

To unscrew the nut it will be necessary to apply a strong heat (about 250 degrees with a hot air gun)

http://na.henkel-adhesives.com/industrial/product-search-1554.htm?nodeid=8797714219009



It is used at many points stressed by vibration on the rotax engine 348/560/654/655/990

 

[Rotax_655]

Here is a nicely doumented altertative washer sollution:

Sorry but I think this test is too short
Vibrations in an engine are extremely variable as amplitude and can last for hundreds of hours.
It's not just like a train carriage ....

 

[Flynn]

What I don't understand is how the washer can be loose when the nut is not? It's as though the washer is too thin for the nut to clamp it anyway.

Rotax_655 are you using a standard washer or the NordLoc?

I need to make a decision whether to use Nordlocs or the standard washer as well as the locktite.

I don't think the nut is loose, just the washer behind it, but I want to make sure and I don't want to strip it down once to find out and then again to replace the washer.

 

[EricV]

I'll be the first to admit that I don't know, but perhaps it's that the nut has reached as far as it'll go on the threads (meaning it ran out of threads to spin down on)- which is not far enough to fully tighten down against the washer making it immobile. So if such is the case perhaps a thicker washer?

 

[Rotax_655]

To decide, you must first understand why the washer is slow when you sharpen the nut. This situation is not normal in my opinion

 

[sh0Cked]

You have to bend the washer FYI.

 

[Flynn]

Well I don't know what you mean by bending the washer, but I observed that the old washer was dome shaped and the new one was flat.

Anyway, I noticed that when the nut was done up to 70nm, it wasn't all the way flush down the thread.

I had to tighten it to about 150 to make it go all the way to the end of the thread and it was still on the shaft as though it was cross threaded but wasn't.

Also re the locttite 648, it was not necessary in the end.

I checked the torque of the flywheel nut and the counter balance shaft nut and they hadn't loosened at all, both the torque that I did them up to, both with Bossil high strength threadlock, bought from eBay along with blue for £10.

But since I'd already bought the Loctite 648 I reassembled it with that anyway.

And the rattle has gone! I was sceptical, thought it was probably something random causing the rattle, but obviously it was that washer all along.

So the secret it that you need to tighten the nut more than 70NM, because something resists the nut going on up to a torque of 70NM.