Cam bearings went out

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fast moto · #1 Post by **fast moto** » Wed Jan 22, 2014 12:18 am

went riding in glamis for MLK weekend and the cannondale started making a weird sound, i was about halfway back to camp when the bike came to a grinding stop, I had to have my friend tow me back in. when i got home i pulled the motor and found that the cam bearings were out, the ball bearing on the intake cam had completely disintegrated and the exhaust was on its way, the needle bearings on the water pump side of the motor for both cams was also going out.

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This is the second time i have lost cam bearings with this motor the first time i caught it early before it did any major damage this time i was not so lucky, there was plenty of oil in the head and around the bearings when i pulled the motor apart and i know i torqued them to the proper specs. any ideas on why this keeps happening?

What do you think of the head, ruined or still useable?
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The intake valves clearly made a little contact with the piston, i still have to check the valves but do you think the piston will still be ok after taking a hit from the valves?
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fast moto · #2 Post by **fast moto** » Wed Jan 22, 2014 12:24 am

The cam bearing chewed into the engine cover putting alot of shavings in the transmission and chipping the gear.
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the scavenger pump also got damaged from the bearing bits, do you think the crank plate is still good?
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fast moto · #3 Post by **fast moto** » Wed Jan 22, 2014 12:28 am

One more question what do you think about the dark spot on the stator (the quad did die out of nowhere a few times, don't know if that was the cams or a bad stator)
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MX Quad Dad · #4 Post by **MX Quad Dad** » Wed Jan 22, 2014 3:00 pm

I won't comment if any of the parts are reuseable but I am wondering because I had bought a Cannibal with a cracked case and it had very few hours on the rebuild and when I tore it down the cam bearings were bad. the seperators for the balls were tore-up. I don't have any hours on it after swaping the case and may be a little worried now.

Few questions, what about the history of the head. do you know if the bearing caps were ever switched? were they ever over torqued? Did the gear end bearing press on easy? is the deomp still all intact?

The last question is how were the cam gear bolts removed and retorqued. with the chipped teeth it may be a sign that someone clamped the gear in a vise at one time.

kdeal · #5 Post by **kdeal** » Wed Jan 22, 2014 3:57 pm

Do you guys remember in the other post for Whogives a6 that I stated I send my heads to Tim? One of the things Tim does (that my local machine shop doesn't do) is check the line bore and clearance on the cam caps to bearings. What happened to your motors most likely was that the clearance was too loose or tight and the bearing wore out way too soon. This is why it happened again so quickly. The threshhold for clearance on that bearing is only 1 or 2 thousandths.

PLEASE make sure you clean out every nook and cranny on that motor for ground up ball bearings and shavings. I have seen several people put these motors back together only to fail again because of a loose ball bearing somewhere. I would also flush the frame.

Been there done that.....
Ken

kdeal · #6 Post by **kdeal** » Wed Jan 22, 2014 4:04 pm

The head cam bearing saddle looks reusable with a clean-up. The intake valves are probably bent. CHECK ALL 4 OF THEM for straightness. The piston doesn't look bad. I would check the connecting rod for being bent. The cartridge plate looks like you can file the roughness down, trash the ge-rotor gears in the scavenge pump, check the inside of the housing. The cam gear is wasted. The stator should just be checked on a meter while the motor is running. I may have some spares you can use, let me know.

fast moto · #7 Post by **fast moto** » Wed Jan 22, 2014 6:40 pm

I far as I know the caps have never been swiched. I may have over torqued them the first time I rebuilt the motor causing them to fail the first time. But when I rebuilt it this last time I sent my head to tim to be ported so I assume he checked the cam bores and they were fine. Gear end always pressed on fine and the decomp is perfect. I never put the gear in the vice when I removed the bearings, I think those chips are from the gear shaking around ounce the bearings went.

kdeal · #8 Post by **kdeal** » Wed Jan 22, 2014 10:13 pm

If Tim went thru it the 2nd time I agree. BUT, if you loosened and tightened the cam caps after getting them back and you went over about 10 foot lbs on the bolts the same thing can happen. The cam caps are torqued right before I put the valve cover on. I have left one set of cam bolts hand tight only and paid the price for it by them coming loose and ruining a brand new FX400 cam!

fast moto · #9 Post by **fast moto** » Wed Jan 22, 2014 10:59 pm

This time i will make sure the torque wrench is calibrated before i reassemble the motor. Clearly I can???t reuse the old caps anyways. I do however have a spare fully assembled (fx400) head minus the port job, should I use the caps off the spare head on mine? or should I just have Tim port my spare head and run that one?

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MX Quad Dad · #10 Post by **MX Quad Dad** » Wed Jan 22, 2014 11:43 pm

QUOTE (fast moto @ Jan 22 2014, 05:59 PM) <{POST_SNAPBACK}>

This time i will make sure the torque wrench is calibrated before i reassemble the motor. Clearly I can???t reuse the old caps anyways. I do however have a spare fully assembled (fx400) head minus the port job, should I use the caps off the spare head on mine? or should I just have Tim port my spare head and run that one?

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either way but, if you use caps from another head you will need to have it line bored or at least have them checked