Were all cranks duff?

Message

marshall100 · #1 Post by **marshall100** » Fri Oct 21, 2011 3:13 pm

Just wondered if every crank suffered from being badly balanced? were some better than others or is it just a general 'they're all bad' kind of thing. I know the bearing in mine will need doing at some point and while the two are slightly related if the engine isn't hammered then will it definately go bang?

ry415 · #2 Post by **ry415** » Fri Oct 21, 2011 3:43 pm

I have an 02 motor with plenty of hours on it I'm the 3rd owner pulled the crank early this year to fix the one way bearing on the clutch and opted to do the z bearing update. 2 Crank specialist out here check the crank and said I was nuts for splitting it and putting the Z bearing in but we did it anyway because everyone on here says to do it. I've read somewhere the 02 cranks were the best so maybe thats why.

Just a month ago we had to pull the crank again so we checked it and its still perfect...suspected it wasnt because the bearing on the stator side went out but upgraded it.

Happyboy · #3 Post by **Happyboy** » Fri Oct 21, 2011 6:18 pm

The 03 cranks were the worst in terms of balance. All of the cranks had issues with the main bearing. The problem not being the crank itself, but the bearing. The bearing that was used was just insufficient for the usage. Now, it was a total crap shoot when it came to bearing failure. Some failed very quickly, and some have lasted for years. They all ripped into the crank pin to some degree. That is actually where the "failure" of a non-failed crank came from. When you pulled the good crank apart many times (most times actually) the bearing had actually ate into the the pin and would leave a groove on the inside edge, as well as pitting along the center. Using a crank in this condition is just bad juju as it will fail at some point even with a new bearing.

kdeal · #4 Post by **kdeal** » Fri Oct 21, 2011 6:47 pm

The later model cranks were casted and the casting slag is uneven around the crank. The connecting rod was also changed to a different design and the two things caused the balance issues. Some where better than others. The connecting rod big end bearing was a mis-designed item. Cannondale only sold whole assemblies and not the parts. Timbo does a few mods to the newer cranks when updating the bearings that puts them in a more balanced state. You will know when he has done a crank by looking at the material removed around the pork chop of the crank.

I just pulled a motor apart the other day that had the machining and a Timbo made connecting rod on it. I know this will be a good crank. LOL

marshall100 · #5 Post by **marshall100** » Sat Oct 22, 2011 8:50 am

That's well worth knowing. I've done all the mods on my 2002 speed bar the crank bearing. I don't and never have rev'd the guts out of it so I'm really wondering for the sake of some piston rings, does it need to be done?

I have a spare motor to rebuild anyway so I'll carry on doing that. I love this place, so much interesting information that's readily available.

wistech · #6 Post by **wistech** » Sat Oct 22, 2011 2:01 pm

http://www.cannondaleriders.com/forums/ind...ic=7606&hl=

Who started the myth that the rod bearing failures were due to balancing? Sorry most of the pics were lost . I think when explaining the exact cause for the crank bearing problem it should be clear that it is the incorrectly specd bearing cage rubbing on the rod journal and then pin that causes the eventual crank failure and not the rollers . To ignore this serious problem is just asking for a very expensive repair and failure at the worst time.

kdeal · #7 Post by **kdeal** » Sat Oct 22, 2011 2:23 pm

I guarantee you that pretty much any late model crank is not balanced as it should be. Did this cause the rod bearing failures? NO. This was the misdiagnosis from the factory and else where. Everyone worked on rebalancing everything instead of the real problem..... the ripsaw bearing! But, no one has ever been able to describe reasonably why the bearing goes out in just a few hours or sometimes lasts many, many hours. I think the acceleration of the problem could be linked to the inconsistent balancing of the late model cranks. Now...... what about the earlier model cranks? See what I mean?

wistech · #8 Post by **wistech** » Sat Oct 22, 2011 2:45 pm

Oh almost forgot it was ATK and their idiotic weld jobs on the crank balance holes that perpetuated the myth.

marshall100 · #9 Post by **marshall100** » Sat Oct 22, 2011 5:22 pm

So, in summary, it's still wise to pull the engine and change that bearing? thus saving the rod as well?