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wudangprod

Engine grinding - Help please

5 posts in this topic

So I recently bought an 03 yz450f for pretty cheap. Only thing was that the bike wasn't running. The seller said it ran fine the last time he rode it which was 5 years ago, and since then the bike had been sitting. So I get the thing home, drain all the fluids (i do notice a lot of shavings in the oil filter ), put new fluids in there. I pop all the engine covers, see how things look. I check the valve clearances and cam timing, which are all good, I also put a new plug in. At that point since the compression and spark are good I'm thinking the carb is the issue. I pull that bad boy out and take it apart, sure enough, it had gewey old gas in there so I rebuilt it and cleaned it up nice. I put everything back together and takes me a few kicks but she fires up, I let her warm up and take her for a quick test ride. Everything seemed good until I hit 3rd gear at which point she started grinding really bad and stopped. I push her home, kicked it once or twice and the compression just didn't feel good (not smooth/ hard). I pull the head cover and on the cam chain side on the inside of the cover are a bunch of tiny plastic chunks. I pull the crankcase cover of and there are some in there too along with a couple metal pieces. I know I'm basically f***ed but I guess I'm curious on how bad. What needs to be fixed? How much will it cost? Thanks for any input

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So i pulled the top end off and, it looks like the cam chain grinded through the chain guards. and the timing is all messed up. How could this have happened? what is the next step

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If the head is actually off, test the valves to see if they are bent from contacting the piston by pouring solvent (paint thinner, mineral spirits) into the ports.  Normally, they may seep a little, but if the solvent runs right out past the valve, you have a problem. 

 

If only the cam cover is off, remove the chain and see if the engine has compression.  Should have quite a lot without the decompressor working. 

 

You will have to pull the head to replace the chain guides anyway.

 

The likely cause is poor lubrication due to inferior oil and/or excessively long oil change intervals, and most likely started as a kinking cam chain.

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If the head is actually off, test the valves to see if they are bent from contacting the piston by pouring solvent (paint thinner, mineral spirits) into the ports.  Normally, they may seep a little, but if the solvent runs right out past the valve, you have a problem. 

 

If only the cam cover is off, remove the chain and see if the engine has compression.  Should have quite a lot without the decompressor working. 

 

You will have to pull the head to replace the chain guides anyway.

 

The likely cause is poor lubrication due to inferior oil and/or excessively long oil change intervals, and most likely started as a kinking cam chain.

 

Hey thanks for the answer. I'll try the paint thinner tomorrow, but it looks like the intake side is bent. I'm going to tear the whole motor apart to clean it all up and find out what else is damaged and if anything else needs to be replaced. What should I be looking for?

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Yup, if there's no cam in that head, the intakes are jacked.  The valve guides are probably damaged as well by the look of things.  As far as what to look for, just check the condition of everything you see in there and evaluate it.

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