Its time for crank updates

Message

wistech · #1 Post by **wistech** » Fri Aug 20, 2004 9:32 am

I decided to pull apart a still running 100 hour 02 crank to see how its wearing. The pin is in very good condition with no sign of the cage touching it. The rod on the other hand has deep but smooth wear on both edges where the bearing cage has been rubbing . If you look close at the pic you can see rollers are only touching the center half of the rod. I will be taking all my engines down and installing new rods and the z400 bearing /pin . Many talk of balancing to be a cure but a bad bearing is a bad bearing. If the stock cranks can be fixed before major wear occurs then a $35 bearing should extend the life of our cranks tremendously. If you are pulling your motor to do the stage 8 then there would be no better time to fix this timebomb also.

NRath · #2 Post by **NRath** » Fri Aug 20, 2004 4:11 pm

Some people either have too much time or too many quads!! Pulling apart an engine that's still running? You should have been off riding it!

Seriously, that's some interesting info. That looks like a newer crank/ late '02, right? The bearing- I'm assuming it must not have in inner or outer race, right? It's riding directly on the pin and in the rod? If that's correct, the problem is the cage is floating around and gouging the inside of the rod and the pin. That's probably not the actual problem, I'd have to think the cage is what is getting damaged, then allowing the bearings to move around and break up. I haven't seen a crank apart yet, so this is mostly just ramblings. Sounds sensible to me, though.

Whadda' ya' think?

wistech · #3 Post by **wistech** » Fri Aug 20, 2004 5:06 pm

This is Feb 02 engine. It was getting weak because of a cam lobe wore out. Yes its a one piece cage and was still able to retain the rollers after disasemmbly so its not damaged in any way. The rollers are good and the crank didnt have any radial endplay. But the small end of the rod had more wobble than it should have. This was because the rollers were only touching the center of the rod journal. The outer quarter inch of both sides of the rod journal have been slowy ground down from the cage itself. The cage should float on the rollers all the time and never contact the bearing journals . How could that not be the problem? If the wear gets worse the sides of the cage will start cutting into the pin due to excessive slop.

cannondale27 · #4 Post by **cannondale27** » Fri Aug 20, 2004 7:11 pm

You mean big end.Wistech wanted to catch this early and did in later stages the cage will also eat at the crank pin.

wistech · #5 Post by **wistech** » Fri Aug 20, 2004 7:51 pm

I meant if you held the small end with your hand you could actually wobble the big quite a bit. I will post pics of the outside of the cage tonight. The part that rubs on the rods surface has been honed to a razor sharp edge in the gaps between the rollers. Right where your thumb is in your pics steve.The damage to the pin must be caused in the later stages of cage wear because the pin I have only has wear from the rollers . You know had this been a brass coated bearing cage or made completely out of a softer material rubbing on the bearing race might not be such a big deal but this cage is made of steel.

cannondale27 · #6 Post by **cannondale27** » Fri Aug 20, 2004 8:39 pm

Yup just like a dang saw!Hmmm what is the better bearing.z400 has copper cage that just seperates the rollers.

cannondale27 · #7 Post by **cannondale27** » Fri Aug 20, 2004 8:41 pm

Here is another.

wistech · #8 Post by **wistech** » Fri Aug 20, 2004 9:28 pm

Copper cage,more rollers. Z400 pin . Thats got to be a vast improvement over the stock setup. I hope I can save the rods on my other engines but I fear they will all have been worn beyond repair.

kdeal · #9 Post by **kdeal** » Fri Aug 20, 2004 10:12 pm

Is it possible that the rather large side clearances found on the factory Cannondale cranks, (I think Steve said at the spec maximum .018) can cause a rocking effect with the rod that is causing the bearing to fail prematurely? There is no discoloration on the rod journals to give any evidence of a heat or lubrication problem. I would think that side load + vibration (out of balance) could attribute to this??? What about the pin to bearing to rod inside diameter clearances? Do you think a better bearing (Z400)& tighter initial rod side clearances would help the situation?

Just a thought.

wistech · #10 Post by **wistech** » Fri Aug 20, 2004 10:35 pm

Im going to have to say no on that. I dont think the bearings are rocking at all during operation. Its just that when the edges of the rod journals are worn off by the sloppy cage chewing it up there is only the center of the needles left to handle the load. Even on my siezed crank the needles were still in tact. The cage was ground up and evenly distributed through my oiling system. Im not sure crank balance could have an effect on the rod bearing . The main bearings and engine castings will definitly be affected .