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Discussion Starter · #1 ·
Hi

I`m now about to reassemble the engine on my 1000S from 2004. As mentioned in an earlier thread, the conrod-bolts on cyl. 3 had come Loose and were only hanging in a few threads, when I took the engine apart.
I bought another complete crankshaft on Ebay from a dealer in UK. According to the seller this engine had only done 3000 miles when the bike crashed. The complete engine was sold as spare parts on Ebay. The crankshaft looks and feels like new and I believe the seller told me the truth regarding the mileage of the crankshaft.
After the 2 loose conrod-bolts in the original crankshaft my intention was to replace all conrod bolts in the "new" crankshaft and even though the engine manual does not recommend use of thread-locking fluid on conrod-bolts I would use it.
I`m just about to order the parts needed to reassemble the engine and I see the conrod bolts are quite expensive?? and (according to the manual) also a bit tricky to assemble by measuring how much the bolt is elongated. Do any of you guys have so much experience with these engines so you could advise me if I should replace all the conrod-bolts or not

Best regards
Preben
 

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I wouldn't replace them.....or use Loctite either



:popcorn:
 

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Old Wing Nut
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The new crank came with rods assembled? Looks like a new piece in the photo. If so I say leave it alone.

MV manuals advise to always replace con-rod bolts at each use.

Replacing the con-rod bolts requires that you measure each bolt length with a micrometer prior to installation. Oil the threads in the con-rod cap and torque the bolts to at least 50 nM, then measure the bolt length again with the micrometer. The bolt must be within 0.2 to 0.22 mm longer or the torque needs to be increased until they are. This is measured stretch and why you need to use new bolts and only the special bolts specified by MV.

And unless the manual calls for a thread locking agent you should not use one. On the con-rods they call for oil on the threads to enable correct torque and stretch.
 

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Hmmmmm

I wouldn't replace them.....or use Loctite either



:popcorn:
Tell me more Knurl :)
I am in the exact same boat with the bolts.
Even called ARP to see if they sold something in the same dimensions (in hopes of a cost cut) and they said they didn't have anything to match :'(
I would like it if I didn't have to spend my "to my self" xmas money on a set of conrod bolts :)

Tree
 

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What Noel is saying, I believe, is to leave the assembly as is.
Ed has stated that's what he would do...and he knows a thing or two about bikes.

If you can't afford to replace the bolts, and you can't perform the job within spec, then leave the assembly as is and enjoy.
 

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How much are these bolts ?

and these boys know what they're saying. If the crank is ok , leave the bolts alone. It wouldn't even cross my mind to mess with something the factory has assembled, for no good reason... It's not as though they say to take these bolts out and replace them at service time.They are there for the duration aren't they ? :)
 

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How much are these bolts ?

and these boys know what they're saying. If the crank is ok , leave the bolts alone. It wouldn't even cross my mind to mess with something the factory has assembled, for no good reason... It's not as though they say to take these bolts out and replace them at service time.They are there for the duration aren't they ? :)
DUDE!!!
like $44 each!. :-O

That is why I tried ARP, because I am doing a full disassembly and am going to need to replace all of the bolts. :'(

Tree
 

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Discussion Starter · #8 ·
Hi Guys

Thanks for your replies. The crank came to me with the conrods on it. As I have no experience with these engines yet, I thought I better ask someone about it:) With these replies I`m convinced I`ll leave the crank as it is and build it in my engine.

Preben
 

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The problem with these engines is that it is normally the big end shells that go first and not the mains so based on the amount of popped engines I've seen I'd pull the rod shells apart.

It's easy and cheaper to do it now with the engine stripped than to fire it up and then have an issue.

When these rods go they don't rattle as you'd expect they just go tight and the nip up.

I reckon you can get two uses out of a set of rod bolts and in the grand scheme of it I would rather put new shells in the rods and use the old bolts.

Big ends and rod shells are this engines biggest weak spot, new everything every time. Oh and you'll never ever get the correct clearance according to the manual with plastigauge either, they come up loose all the time and I've given up stressing to try and match it, I just go for as tight as possible.

If you can afford to have the engine in and out then leave it, if not then invest a bit now to save possible costs further down the line. :)
 

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The problem with these engines is that it is normally the big end shells that go first and not the mains so based on the amount of popped engines I've seen I'd pull the rod shells apart.

It's easy and cheaper to do it now with the engine stripped than to fire it up and then have an issue.

When these rods go they don't rattle as you'd expect they just go tight and the nip up.

I reckon you can get two uses out of a set of rod bolts and in the grand scheme of it I would rather put new shells in the rods and use the old bolts.

Big ends and rod shells are this engines biggest weak spot, new everything every time. Oh and you'll never ever get the correct clearance according to the manual with plastigauge either, they come up loose all the time and I've given up stressing to try and match it, I just go for as tight as possible.

If you can afford to have the engine in and out then leave it, if not then invest a bit now to save possible costs further down the line. :)
X81
Are you suggesting, for street use, the bolt could be re-used once (just a question)
I see a lot of back and forth on this issue

Tree
 

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The big end bearing is the most heavily stressed bearing on any plain bearing engine. On the Jap bikes it is a big end bearing that lets go every time. Never a main alone unless the builder really screwed up, or the oil supply was dirty.

When the bearings begin to wear excessively (generally from lack of oil supply) the shells will skid and try to slip over or under each other, seizing the rod to the journal, then "snap"...

From what I have seen in photos on this forum, it would appear Rod bolts coming loose or breaking has caused big end failures, not bearing wear, but I haven't seen the pieces in person.

Tree, you could probably reuse the bolts, but you need to go for a straight torque number and forget stretch, as that has already occurred. More stretch is going to weaken the bolt......resulting in what I have mentioned above.

Racing or street, bearing loads don't know the difference....just they are constantly high on a race engine and only occasionally maxed out in a street engine.

You pays your money and you takes your chances.

But Chris has seen the insides of more MV engines than I have.....so I defer to his experiences.
 

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bolts.....

you can reuse them until you exceed the Modulus of Elasticity......

in other words.......the yield point and deform the bolt :jsm:


ever see bolts in a tension tension fatigue machine?????

didn't think so......good bolts will go 10^7+ cycles

http://en.wikipedia.org/wiki/Yield_(engineering)


the people that want you to replace rod bolts are the ones selling them

:naughty::naughty::naughty::naughty:


:popcorn:
 

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Discussion Starter · #14 ·
Hmm - different opinions regarding con-rod bolts and the use (re-use) of them. I guess though my main concern is to reassemble the engine without really knowing what went wrong with the big end on cyl. 3. Will it do the same again after another 11500 km??

By the way after changing crankshaft can I use the same size cylinder head gasket or will I have to measure the piston/cylinderplane distance as described in the manual?

Preben
 

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Those bearings wore from lack of lubricant.....oil supply to that journal must have been low for some reason. What do the other beings look like?
Of course, that lubricant related failure could also have been due to improper clearance, either too little or too much, preventing the oil from forming the cushioning layer between the bearing and journal (can't get in or gets out too fast). That's why I wonder about the other journals.
Seems that #3 is the frequent failure...inherent design issue carried over from original lower stress 750 engine design?

Noel, I've watching failure testing in the QA labs where I used to work. Lots of fun seeing metal bits being torn to pieces. Amazing machines.

About replacing the rod bolts...like I said...Ya pays your money and Ya takes your chances.
 

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Hmm - different opinions regarding con-rod bolts and the use (re-use) of them. I guess though my main concern is to reassemble the engine without really knowing what went wrong with the big end on cyl. 3. Will it do the same again after another 11500 km??

By the way after changing crankshaft can I use the same size cylinder head gasket or will I have to measure the piston/cylinderplane distance as described in the manual?

Preben

Use, replace , shall I, Shan't I ?

It all depends. Noel is right,Chris is right and Ed is right. Everybody is right.

What if the bolts were "OVER TORQUED" in the factory ? That's a game changer innit ?

As the man famously said " Feel lucky ? " Go ahead...:smoking:
 

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wasn't the read Knurl was talking about (the link) talking about plasticity and elasticity.
Reading that answered everything I was wondering about.
But! I am not an advocate of anything other that do what you can handle.
..........
I got this ;-)

Tree
 

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Joe;

given that this the 1st #2 rod I remember going......we've had several pictures of the rod bolt nuts unscrewed and a trashed motors
but it was ALWAYS #3

I suspect the Factory uses a machine to torque the rod bolts....and the sensor on #3 is erratic........trust me, the Chief Engineer got a message:)

I also think Chris is right......
with loose bolts.....you lose oil pressure....then as the shells go away, then bypass the notches in the rods and lock the motor up

I don't like the straight shank on the rod......you never break rods at the top

the way they are supposed to look......

http://c767170.r70.cf2.rackcdn.com/R65000.jpg

Carrillos, real rods forged out of the best metal you can get....and before

someone says what about Pankl?????? Carrillo owns Pankl

:naughty::naughty::naughty:
 

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Joe;

given that this the 1st #2 rod I remember going......we've had several pictures of the rod bolt nuts unscrewed and a trashed motors
but it was ALWAYS #3

I suspect the Factory uses a machine to torque the rod bolts....and the sensor on #3 is erratic........trust me, the Chief Engineer got a message:)

I also think Chris is right......
with loose bolts.....you lose oil pressure....then as the shells go away, then bypass the notches in the rods and lock the motor up

I don't like the straight shank on the rod......you never break rods at the top

the way they are supposed to look......

http://c767170.r70.cf2.rackcdn.com/R65000.jpg

Carrillos, real rods forged out of the best metal you can get....and before

someone says what about Pankl?????? Carrillo owns Pankl

:naughty::naughty::naughty:

So we're all right lol :smoking:

Do we have a count on bikes that have lost their rod bearings ? How much of a problem is it by numbers of victims ?

joe
 

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Joe;

given that this the 1st #2 rod I remember going......we've had several pictures of the rod bolt nuts unscrewed and a trashed motors
but it was ALWAYS #3.

I suspect the Factory uses a machine to torque the rod bolts....and the sensor on #3 is erratic........trust me, the Chief Engineer got a message:)
Noel,
Didn't Pretrida say this was #3 also?? Just went back and read the original post again...Rod bolts were loose, hence loss of pressure and bearing wear.

The good thing here is the owner stopped the motor when the banging began......the squids that ride the HonKawSuzYam bikes I see where there is Main and Rod bearing wear (or broken rods) generally just kept on keeping on in spite of the banging and oil pressure light....."must get home, it'll be OK, warranty will cover it"!!!! :bash:

I'll go back to my first statement....leave the new crank alone.
 
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