Camshaft sprocket's bolts snaped!!! - MVAgusta.net
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post #1 of 17 (permalink) Old 05-22-2013, 02:36 PM Thread Starter
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Camshaft sprocket's bolts snaped!!!

Yep, major shit!

I've been on a nice trip on Saturday on my 2009 989R. I heard some weird noise from the engine, like a little bell. I thought that cam chain tensioner went and since I was near home I thought it will do.

Well it didn't! The noise was from exhaust cam sprocket banging on the cam flange and eventually both of them snapped. Luckily I was on a straight part of the road, going slowly and I pulled the clutch in very fast.

I don't know how this happened. It probably is my fault since I was doing the valve clearance adjustment job a year ago. But for the bolts to just shear off? I have done this a few times on the MVs, so...I really don't know...

Well, I found both of the bolts and all the Nordlock washers. Bolts and 2 washers were in the head and 2 washers in the sump.
I pulled the head and the valves didn't touch the piston, can you believe it? The exhaust valves leak a bit, so I will do the valve job, put everything back together and call it a day. Of course, I pulled the oil pump and will clean everything well before reassembly.

Looking at the bolts, they didn't untighten as there is still a large part of them sticking out of the cam flange. The bike has around 17000 km.
Any one with an explanation?
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post #2 of 17 (permalink) Old 05-22-2013, 03:38 PM
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looks like a major disaster. i am happy no accident happened
and wish you the best with fixing the damage. can it be that
the cam shaft actually remained fixed with the exhaust valve
closed, while the cam chain was still turning?
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post #3 of 17 (permalink) Old 05-22-2013, 04:03 PM Thread Starter
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Yes, the camshaft remained fixed, the sprocket was turning on the camshaft.

In the 4 cylinder, there is a valve (or a pair) opened at all time, so it is a miracle that the piston didn't hit the valves.
The only damage is some seals that I have to buy and a lot of time.
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post #4 of 17 (permalink) Old 05-22-2013, 08:51 PM
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Looks like you got lucky. In a strange kinda way.
It's good that you can do the work yourself.

I appreciate the pics as I've never been into an MV before. I do porting/cylinder head rebuilding so it's very informative.

I know it sucks but would you mind taking pics of the ports and combustion chambers while you're in there?

I was going to offer to port it for you while it's apart but I see you're far away from me. If you don't mind the down time let me know.
I have references and you can see some of my work on youtube if interested.

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post #5 of 17 (permalink) Old 05-23-2013, 01:14 PM Thread Starter
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Will take pictures for you, no problem.

Thanks for the offer, but I don't like the idea of the head being shipped half across the world and then back. If I would live near to you, I would do it in a heart beat.
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post #6 of 17 (permalink) Old 05-23-2013, 01:22 PM
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Originally Posted by MihaSLO View Post
Will take pictures for you, no problem.

Thanks for the offer, but I don't like the idea of the head being shipped half across the world and then back. If I would live near to you, I would do it in a heart beat.
Thanks!

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post #7 of 17 (permalink) Old 05-23-2013, 03:00 PM Thread Starter
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I sent you pictures on the email you have listed under your profile.
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post #8 of 17 (permalink) Old 05-23-2013, 06:01 PM
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All fasteners stretch. The cam sprocket bolts were stretched once when the engine was assembled and then again when you set the valves. So, perhaps when you re assembled the engine you fastened the already stretched bolts to the correct torque and that was just too tight which would cause them to shear.

I'm just guessing here but it sounds good, doesn't it? I'm sure Noel would have an opinion on this and the engine builders too.
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post #9 of 17 (permalink) Old 05-23-2013, 08:09 PM
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Quote:
Originally Posted by MihaSLO View Post
Yep, major shit!

I've been on a nice trip on Saturday on my 2009 989R. I heard some weird noise from the engine, like a little bell. I thought that cam chain tensioner went and since I was near home I thought it will do.

Well it didn't! The noise was from exhaust cam sprocket banging on the cam flange and eventually both of them snapped. Luckily I was on a straight part of the road, going slowly and I pulled the clutch in very fast.

I don't know how this happened. It probably is my fault since I was doing the valve clearance adjustment job a year ago. But for the bolts to just shear off? I have done this a few times on the MVs, so...I really don't know...

Well, I found both of the bolts and all the Nordlock washers. Bolts and 2 washers were in the head and 2 washers in the sump.
I pulled the head and the valves didn't touch the piston, can you believe it? The exhaust valves leak a bit, so I will do the valve job, put everything back together and call it a day. Of course, I pulled the oil pump and will clean everything well before reassembly.

Looking at the bolts, they didn't untighten as there is still a large part of them sticking out of the cam flange. The bike has around 17000 km.
Any one with an explanation?
Hi Miha,how LUCKY the head of the allen screw didn't damage a cam lobe or get caught in the chainusing a screw with a shank(non threaded section)the width of the cam sprocket would be my approach.Cheers Steve
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post #10 of 17 (permalink) Old 05-24-2013, 09:29 PM
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Thumbs up lucky Miha

Miha;
my friend you got VERY lucky

the bolts failed in tension......they're in shear

tensile fatigue life in bolts runs from~ 2x10^6 to 6x10^6 cycles

junk bolts or over torqued (i doubt it was by Miha)

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