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Early 8V motor 'Cyclic rattle'.

P

Penis Rotor

GT Godfather!
Joined
Oct 28, 2008
Messages
2,833
Location
Bungendore, NSW Australia
Well, it looks like the factory finally got sick of people asking 'Why does my 8V motor sound like a gorilla juggling saucepans in a tumble drier?' I'd wondered why my, and other early 8V's tend to be so hideously noisy from the top end. It has always been thus but after I did the cam recall or at least shortly thereafter I started getting what others have described as a 'Cyclic Rattle' from the top end. It goes away not much above idle and I'd always assumed it was related to the tappets spinning, it occurs with about the right frequency, and it may still be related to that but the 'Change' that has been instigated in the 'Newer' motors and presumably this is why they are so much quieter is that the camshafts are now shimmed for end float!

GU08800_45.gif


See part #31? Well that's new. It comes in five sizes.

Part #'s are

CM162701- with thickness of-1.02
CM162702 1.05
CM162703 1.08
CM162704 1.11
CM162705 1.14mm

Dial guage on end of cam through breather vent. biff one way, biff the other, measure clearance in 't'other end of cam-box. add shim to reduce end float to just under 0.1mm/4 thou.

Mine makes the 'Cyclic Rattle' at idle. If you think I'm going to be arsed to take my cam-boxes out just to get rid of that noise you'll have a long wait! :lol: Maybe some other people's is much worse. Me? I just wear ear plugs!!!!! :shock:

Pete

(PS. our importer hasn't got 'em on the shelf yet because despite Guzzi having the picture of the parts up on the parts site weeks ago they denied all knowledge of the existence of the shims :mrgreen: ! I've ordered two of each. Buggered if i know when they'll arrive!)
 
The number 31 suggested it is an afterthought :lol:

Pete, do you think the shim can be retro fitted to the earlier 8V (ie. A5 engine) heads if necessary?

Cheers,
Phang
 
What is the exact mechanism detail that produces the sound? I mean, what happens and we hear it? Is it getting louder as tolerances increase as the engine ages?
 
Mi_ka said:
What is the exact mechanism detail that produces the sound? I mean, what happens and we hear it? Is it getting louder as tolerances increase as the engine ages?
Click to expand...

Mate?? What am I? A fucking magician? How the hell would I know?

The obvious answer is that they first of all designed something that worked. Then they got round to fine-tuning out the stuff that made people who sit down to pee unhappy.

If it's making a knocking noise one can, quite reasonably in my book, assume that it is because something is knocking. What? Choose any one of about twenty places in the top end where excessive play will lead to knocking!

All I can say is that regardless of noise, and I've yet to hear a 'Nuovo Hi-Cam' anywhere near as noisy as mine, the buggers keep on doing their job of hauling the horizon towards one at a rate of knots. So who really cares as long as it isn't doing damage? Not me!!!

Pete
 
On my A5 I do hear it "Slightly" on the right, at 2000-2500 rpm .... ain't bothering me.
Thanks for the diagnostic Pete.

And for the record after a couple of pints I do sit down to pee. :sick:
 
endfloatshim.jpg


Presumably the numbering of the 5 different sizes shim is thickness in mm, that’s 0.03mm increment among the shim.

Working backward, I think the target end float that the factory trying to achieve is 0.01mm to 0.03mm.

Examples:-

If you have a measured 0.04mm end float, the next shim size up in the range will bring it down to 0.01mm

Phang
 
Taking the chance of being flamed by Pete,

I think that the noise may has to do with the very slight length differences bewtween the chain links that occur as the chain is wearing in. Maybe the cam gets oscillating variations on the force applied by the chain and this causes minuscule position changes for the cam that can be related to cam shaft clearances.
I think that the frequency of the sound recurrence is pretty close to the total chain length divided by the circumrefernce of the cam sprocket at the idling rpm range.
Say chain length = 10 times sprocket circumreference.
At 1200 rpm the cam rotates at 600 rpm so the chain makes a full revolution at about 60 rpm or so, which is a 1Hz or so frequency pretty close to the noise recurrence.
If an exact chain length/sprocket circumrefernce ratio is known, then this theory can be examined in better detail.
 
It also seems that earlier motors are NOT retrofitable with the shims unless you opt for the 'New' camshafts so unless we want to spend up big on new cams us owners of 'Early' 8V's will have to put up with the noise like a mid 19th century steam engine from the top end :laugh: .

Personally the noise doesn't worry me and I have yet to hear an 8V as noisy as mine once its hot! Ear plugs are a wonderful thing!!!

Pete
 
Thinking out loud ....
When there was a recall in February 2009, for the 8V ENGINES(GRISO 1200 –STELVIO1200) -BOWLS
http://www.guzzista.com/PressRelease/griso8vandstelviorecall.pdf
The dealer would have had to change the cams on the bikes that were already in use. (Thats if they followed it to the letter.. :roll: )
I know mine was a vehicle in stock and delivered in October 09 so fat chance I have new cams.

but for the owners that are still going through the tappet changes ........ does the service replace them with new cams now?
 
No idea Dan, but the service notice does specify that earlier bikes should continue to use the earlier cams.

I was wondering about the fact that 2010 bikes had different part #'s for the cams. I didn't think the grind had changed because the mapping hadn't, the truncation of the length of the bit with the lobes on explains the difference in the part #'s obviously.

Pete
 
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