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Frank_z28

Blue heat mark on crankshaft

5 posts in this topic

A good friend of mine blew his 04 450 yesterday. We already opened the engine and its the cylinder/piston/ring that gripped. We noticed blue heat spot on the crankshaft ( i will post pic when i go back home after work). Is it normal or the crank have "cook"

Since he need to replate his cylinder wall, is their any big bore combination that can be done ?

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I've heard many different opinions on the blueing on the crank, I've talked to a few knowlegeable people on this who say you cannot go by this for judging whether or not you have a crank problem, reason being that the crank has to get heated (in most cases by torch) in order easily to press the crank pin in, this will blue the crank around that area.

I believe if everything is solid, smooth and works as it should, don't lose sleep over it.

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My brand new, OEM 426 crank had the same markings right out of the box. Check the bearing for radial play and measure the side to side clearence.

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The bluing at the crank pin is normal. It occurs during the manufacturing process. I can assure you, if it happened when riding, the rod would be seized!

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take a special look at the brg on the connecting rod-crankshaft. if that brg has a hard spot it will get momentary stuck on the rotation, that will cause the piston to eat the cylinder wall. It happen on my yam 450

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