Presenting.... ye broken crank
Rex Kramer-Thrill Seeker
SuperBike
Joined: Jan 2011
Posts: 2,312
From: Brookfield, WI
I'm no metallurgical scientist officer guy, but, well, there's your problem!
Wow, really cool looking. Sorry it happened to you Micky.
Just look at how that came apart. Did half snap cleanly and the other half rip apart?
Wow, really cool looking. Sorry it happened to you Micky.
Just look at how that came apart. Did half snap cleanly and the other half rip apart?
Rex Kramer-Thrill Seeker
SuperBike
Joined: Jan 2011
Posts: 2,312
From: Brookfield, WI
Thread Starter
Senior Member
MotoGP
Joined: Apr 2005
Posts: 5,631
From: Montreal
methinks I'll never really get to the bottom of what happened (though some things are coming to the fore, like improper bearing selection during the previous rebuild), but I can guarantee you it's not the oil's fault (quite the opposite in fact)......
Thread Starter
Senior Member
MotoGP
Joined: Apr 2005
Posts: 5,631
From: Montreal
Not much to say. Bike was running fine, I pulled over on the side of the road to make a some small adjustment to my Flo-Commander. I killed the engine and when I restarted it, it was making a terrible racket from the bottom-end. End of story.
RUNLEVELZERO #99
SuperBike
Joined: Jan 2007
Posts: 2,218
From: Skokie
What was maximum and average rpm engine was typically run up to?
Do you commonly rev up and then cut the throttle on the over-run with engine braking?
How much heavier are / were your oversize pistons than OEM?
Thread Starter
Senior Member
MotoGP
Joined: Apr 2005
Posts: 5,631
From: Montreal
as I did not take the engine apart, I have to rely on those that did, and their take is that everything else is fine (again,m it happened at low speed/idle, which is likely what prevented further damage of course).
as for my use, I ride on the street (no track) and work hard at keeping my driver's license, so I mostly ride in the mid-range. 99.9% of my riding occurs in the 3k-7K rpm range. The engine has very seldom been revved above that while riding (though it has been on the dyno quit a few times). I do decelerate with throttle, but again, nothing abusive. I take very good care of the bike and warm it up properly before riding it. I don't do burn-outs and that kind of nonsense as my goal is, and will always be, to make it last and ride it in a respectful manner (considering the money I have invested in it, I want it to last). Oil changes have always been regular (@ 2.5K miles typically) with good quality oil (used Motul 5100 a lot, along with Rotella). Break-in after both rebuilds was long and methodical, with frequent oil changes to carry out the shavings and other crap.
as for the weight of the pistons and rods, the (forged) pistons (despite being 0.5mm oversize) were lighter than the OEM bits, same goes for the rods. Also, the crank was balanced for the new parts, so I dare say the balance factor is closer to optimal than the way it rolled off the assembly line.
In short, I fail to see how anything I did can be responsible for this happening. While I am not an engineer, I work in the powersports industry and spend a fair amount of time around, and discussing with, engineers. This does not make me infallible by any means, but it has given me a good understanding of sound operation and maintenance practices. Take it from there......
as for my use, I ride on the street (no track) and work hard at keeping my driver's license, so I mostly ride in the mid-range. 99.9% of my riding occurs in the 3k-7K rpm range. The engine has very seldom been revved above that while riding (though it has been on the dyno quit a few times). I do decelerate with throttle, but again, nothing abusive. I take very good care of the bike and warm it up properly before riding it. I don't do burn-outs and that kind of nonsense as my goal is, and will always be, to make it last and ride it in a respectful manner (considering the money I have invested in it, I want it to last). Oil changes have always been regular (@ 2.5K miles typically) with good quality oil (used Motul 5100 a lot, along with Rotella). Break-in after both rebuilds was long and methodical, with frequent oil changes to carry out the shavings and other crap.
as for the weight of the pistons and rods, the (forged) pistons (despite being 0.5mm oversize) were lighter than the OEM bits, same goes for the rods. Also, the crank was balanced for the new parts, so I dare say the balance factor is closer to optimal than the way it rolled off the assembly line.
In short, I fail to see how anything I did can be responsible for this happening. While I am not an engineer, I work in the powersports industry and spend a fair amount of time around, and discussing with, engineers. This does not make me infallible by any means, but it has given me a good understanding of sound operation and maintenance practices. Take it from there......
Last edited by mikstr; May 31, 2015 at 05:13 PM.
Well take off, eh.
SuperBike
Joined: Jun 2012
Posts: 1,206
From: QC, Canada
I hope Mikstr won't get mad about this, since I didn't ask him his consent. Anyway, part of the healing process is to talk about it. 
Mike broke his crank due to the fact it wasn't very well done the last time. Perhaps not directly because of lack of knowledge, but, perhaps they didn't understand what kind of vehicle they were dealing with.
Anyway, more harm than good was done to it, rendering it much worst then if nothing had been done to it and left stock.
The crank comes already balanced from Honda at a pretty good level. You could install it without touching it, and you're good. Below is a pic of the broken crank, and all of the holes that have been made to it in order to balance it with the special rods/pistons Mike has in his engine. They basically mist the target. With all those holes, it is perfectly balanced for.....3000rpm's
Just cruising on the highway with stock gearing, you're at 4500rpm's at 120km(70mi). Imagine how much stress was on it when revved up to 7-8000rpm's !!!
So, this is what not to do if ever you find yourself replacing your crank.
Mike broke his crank due to the fact it wasn't very well done the last time. Perhaps not directly because of lack of knowledge, but, perhaps they didn't understand what kind of vehicle they were dealing with.
Anyway, more harm than good was done to it, rendering it much worst then if nothing had been done to it and left stock.
The crank comes already balanced from Honda at a pretty good level. You could install it without touching it, and you're good. Below is a pic of the broken crank, and all of the holes that have been made to it in order to balance it with the special rods/pistons Mike has in his engine. They basically mist the target. With all those holes, it is perfectly balanced for.....3000rpm's
Just cruising on the highway with stock gearing, you're at 4500rpm's at 120km(70mi). Imagine how much stress was on it when revved up to 7-8000rpm's !!!
So, this is what not to do if ever you find yourself replacing your crank.
Senior Member
Back Marker
Joined: Apr 2010
Posts: 219
From: Prague - Czech
Mike broke his crank due to the fact it wasn't very well done the last time. Perhaps not directly because of lack of knowledge, but, perhaps they didn't understand what kind of vehicle they were dealing with.
Anyway, more harm than good was done to it, rendering it much worst then if nothing had been done to it and left stock.
The crank comes already balanced from Honda at a pretty good level. You could install it without touching it, and you're good. Below is a pic of the broken crank, and all of the holes that have been made to it in order to balance it with the special rods/pistons Mike has in his engine. They basically mist the target. With all those holes, it is perfectly balanced for.....3000rpm's
Just cruising on the highway with stock gearing, you're at 4500rpm's at 120km(70mi). Imagine how much stress was on it when revved up to 7-8000rpm's !!!
So, this is what not to do if ever you find yourself replacing your crank.
Anyway, more harm than good was done to it, rendering it much worst then if nothing had been done to it and left stock.
The crank comes already balanced from Honda at a pretty good level. You could install it without touching it, and you're good. Below is a pic of the broken crank, and all of the holes that have been made to it in order to balance it with the special rods/pistons Mike has in his engine. They basically mist the target. With all those holes, it is perfectly balanced for.....3000rpm's
Just cruising on the highway with stock gearing, you're at 4500rpm's at 120km(70mi). Imagine how much stress was on it when revved up to 7-8000rpm's !!!
So, this is what not to do if ever you find yourself replacing your crank.
I wrote it before on UK forum, I came to the same conclusion when installing my lighter pistons. Theoretically new balancing should be done, practically there is nobody around doing it properly (dynamic balancing for whole group, to proper specification), so it is much safer to left it as it is from factory.
Senior Member
SuperSport
Joined: Jul 2018
Posts: 565
Just reading this now after chatting with Wolverine, I use Lindskog balancing here in Mass, https://www.lindskog.com/
They are the authority on this side of the country, on the other side you need to talk to Marine Crankshaft Services. In case anyone else goes this path..
AV
They are the authority on this side of the country, on the other side you need to talk to Marine Crankshaft Services. In case anyone else goes this path..
AV
Senior Member
SuperBike
Joined: Mar 2012
Posts: 1,544
From: New South Wales Australia
Keep us in the loop please,
I can't help but think that for This to happen the engine must be developing some serious grunt.
That coupled with the drilling and balancing of crank is what DONE IT.
Awe well, lesson learnt !
I can't help but think that for This to happen the engine must be developing some serious grunt.
That coupled with the drilling and balancing of crank is what DONE IT.
Awe well, lesson learnt !
Senior Member
SuperBike
Joined: Mar 2012
Posts: 1,544
From: New South Wales Australia
Keep us in the loop please,
I can't help but think that for This to happen the engine must be developing some serious grunt.
That coupled with the drilling and balancing of crank is what DONE IT.
Awe well, lesson learnt !
I can't help but think that for This to happen the engine must be developing some serious grunt.
That coupled with the drilling and balancing of crank is what DONE IT.
Awe well, lesson learnt !
