I seen it. Roostinonyou intake cam broke in two!. Only one valve was working and the other was not opening. What could have caused this on a stock motor? I couldnt believe it when I saw it because it is beefy metal.

 

Hurycne- what a pisser. Any other damage? WAs that from riding at my house? or later?

 

Yikes!!,Athough I have broken a exhaust cam before,The cams seem to be made out of cast iron(can be brittle)Maybe a bad casting?
Were they stock cams?I have stock cams/springs,I dont need.........
Jeff

 

did the bucket freeze in it's bore or is the bucket free, but the valve itself is frozen?

What led up to this happening? Was there an oil change prior to this happening? Could there have been oil starvation to the cams? Was the oil bled properly?

What was the valve clearance before this happened?

Was the motor over rev'd?

 

I know that he had just had the machine serviced. I think hurycne said he went with a syth. oil. Fill us in hurycne!

Scooby- we spend a fair amount of time drag racing. They do run aftermarket cdi's.

 

Did he install new cams? valve springs? piston? RW stage 2? or was it the stock cam that failed?

 

buttfungus- it was a stock cam. Stange- the quad sounded fine and ran. Just low on power like a 400ex.

 

If you guys want to send me the broken cam, I'll get it back to Rotax so they can see what the cause may have been. They were intrested in seeing Jeffs, and cut it apart to test it's internal hardness.

You were lucky, at least nothing else went bad[or at least not much else]when it broke. When Jeffs went, it took out the entire head. The end broke off and the decompressor busted the bucket the valve and the bore it was in. That cost me a bundle to fix[his motor was new, so I covered the repair].

I'm almost sure that your going to have to replace the cam bridge, at least, after this damage. With the shaft broken, you were torqueing sideways on the bridge since it was only suported by one journal. They are only about $90, and well worth that to ensure your new cam holds up. Running the new cam in the wallowed out bore could end up doing alot of damage.

 

Yes it was a stock cam. The valves are straight and the piston is in good condition along with the cylinder and the head. The bridge looks almost new and has no ware on it. He said it was overreved one time and then he lost power. I think it was a bad casting because I overrev all the time.. My first thought was it was because of a valve. Yes this was following an oil change to Redline and all the buckets came right out nothing stuck.

 

Hurycne- Is dusty planning on getting the bomb up and moving pretty quick? Now is a good time to do a little modding.