Cause of a Cracked Cylinder Head?
Posted 26 October 2008 - 07:48 PM
My question is, what would cause the head to crack? The obvious answer is overheating, but, even though I did ride several times on slow single track in hot weather this summer, it never steamed or boiled over. I did have to top off coolant here or there, but nothing out of the ordinary.
I'm concerned about the money of replacing the head, of course, but I'm just as concerned about how to avoid this major expense in the future.
Posted 26 October 2008 - 08:26 PM
Posted 27 October 2008 - 06:32 AM
Posted 27 October 2008 - 08:56 PM
Do you really think Yamaha used "bad aluminum?" Has anyone else had this problem on their WR450? If so, how can I get Yamaha to pay for the replacement?
Posted 28 October 2008 - 05:41 PM
Posted 28 October 2008 - 09:37 PM
Posted 29 October 2008 - 05:43 AM
You may have gotten a head with a casting flaw in it but I doubt Yamaha will do anything for you.
Most of the 450's that I have seen with big bore kits end up with a rod sticking out of the cases.
Posted 29 October 2008 - 07:26 AM
Based on the location of the "meltdown" in the head and the area fried on the head gasket, the excess heat was clearly concentrated around the exhaust port. This makes a little more sense about what may have caused the problem, but I'm still perplexed as to why there was no indication of an overheat (e.g., boiling coolant).
How can I keep this from happening again? Temperature gauge (I don't know what's out there, but I guess I'll start looking), specialized coolant (e.g., engine ice), radiator fans?
Do you guys think it's all due to the big bore kit? If so, how could I help a cooling process specifically for this 487cc?
Maybe I should get rid of the kit to avoid this and, as beezer warns, a rod punching through my case.
Posted 29 October 2008 - 08:13 AM
The bigger motors put out more heat and the cylinder walls are thinner so there are bound to be problems.
I got sick of it and left my YZ450 stock and haven't had a problem....yet.
Posted 29 October 2008 - 08:31 AM
Posted 29 October 2008 - 09:24 AM
Posted 01 November 2008 - 10:43 PM
Here's my question now. In asking the mechanic how I can avoid the big bore kitted engine from overheating again, one of the things he suggested was to use higher octane fuel (than 91). He said it would burn slower and may therefore help reduce the heat put out by the oversized motor. Is this true? I had been running premium gas with no preignition at all.