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Top end rebuild

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So I have a 2004 yz250f rebuilding the top end on it everything's great except for I have a faint line in the cylinder jug do I spend the money on trying to have it bored over or can I leave it and get away with it or should it be resleeve what I'm trying to do is save myself an arm and a leg but I would really like to do it the right way

 

 

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So I went ahead and started to put this bike together and now i have stuck  in between a rock and a cam shaft cover seems as though the cam is grabbing the cover is  not allowing the cam to rotate suggestions  ideas ???

Edited by Landon Pena

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You've over tightened the cam cap bolts

They only require a relatively low torque amount of torque on the bolts and over tightening or uneven tightening results in the cam binding

Edited by GuyGraham

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Cam caps are unique to the head as they are machined to size as a set

Try removing them  and re-assembling them torquing to correct value, in the correct sequence

 

If that fails then the correct repair is to replace or if you can, find a machine shop that will line bore them back to the correct size (the cam cap needs to be bolted up to the head before machining)

To bodge a repair (and I in no way recommend this) is wrap a piece of fine wet and dry (silcon carbide abrasive paper) around an appropriate sized socket and gently try and open up the clearance by rotating it when seated in the cam bearing recess in the head and the cam cap - DO THIS AT YOUR OWN RISK. I once did this on a Yam TDM850 engine which had a binding cam when i checked the valves at 56K miles ( I must have over torqued the cam caps at its first valve check at 28K miles). Last I heard the engine had got to 120K miles with no issues, again this is a bodge and do it at your peril.

Edited by GuyGraham

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So I managed to make it work right can I put the rest of the bike back together is there something I'm missing because I cannot get this thing to run for the life of me reset the timing three different times and still can't get it to run I missing something

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Nice thnks




So I managed to make it work right. I put the rest of the bike back together is there something I'm missing because I cannot get this thing to run for the life of me reset the timing three different times and still can't get it to run I missing something

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Check that your timing is correct. When I put mine back together It wouldn't run because my camshafts were installed incorrectly 180 degrees out! Make sure you use the correct dots/marks on the cam sprockets and always, always use a service manual. I messed up by simply googling "cam timing marks" and it showed me the wrong picture or something. So go back and make sure the correct marks are lined up on your cams. There's two sets of dots......

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Ya as i said that's y i started over and I wasnt at tdc or on my compression stroke with that being said now I'm on my compression stroke all my dots are lined up top dead center new gas new oil new antifreeze new plug new air filter??????

If helps I get an occasional backfire

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