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Discussion Starter #1
what are the differences in the motor between a yfz 450 motor and a yzf 426...
im about to work on a customers dirtbike, its just minor problems, but just wanting to know the differences, just a slightly smaller bore and stroke, and internal oil tank?
 

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Same size bore, 60mm stroke. I believe the head has a few extra bolts more than the yfz's 4 main head bolts and 2 side nuts. I believe the 426 has a manual mechanical decompression system that isnt integrated into the exhaust cam but im not positive. Working on this motor will be basically the same as working on a yfz motor, yzf motor, wr motor, and even yz/wr250f motors. You wont have any trouble working on this motor.
 

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cool thanks, i got it today, his kickstart isent returning, his chain is broken, other minor things, so ill pull off the side cover and see why its not returning! oil filters are interchangable between the 2 right? clutches?

just out of curiousity, i havent heard of the dirtbikes having the oil issue, is this different becuase it has an internal oil tank so it has more splash or somthing? i had a customer ask me about using a WR as a supermotard, and worried about th emotor seizing, but i said alot of people use them for this, but yea they seize on the quads lots so i dont know...
 

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QUOTE (lbyfz450 @ Mar 29 2010, 10:06 PM) index.php?act=findpost&pid=846760
cool thanks, i got it today, his kickstart isent returning, his chain is broken, other minor things, so ill pull off the side cover and see why its not returning! oil filters are interchangable between the 2 right? clutches?

just out of curiousity, i havent heard of the dirtbikes having the oil issue, is this different becuase it has an internal oil tank so it has more splash or somthing? i had a customer ask me about using a WR as a supermotard, and worried about th emotor seizing, but i said alot of people use them for this, but yea they seize on the quads lots so i dont know...[/b]
Oil filters and clutches are interchangeable. The kick lever probably isnt retracting because the return spring probably isnt hooked to the cases like it should be. I also never heard of the dirtbike engines having the oil issue, but the cases themselves are smaller and im assuming they must have better splash the the yfz motor.
 

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Discussion Starter #5
cool thanks....the stopper for the kickstart sheared somhow (the bolt sheared) so the lil plate swung down and i guess it was just spinnig or just in the wrong spot and dident have enough tension or somthing to return,

also his drain plug is stripped, should i heli coil it? or maybe tap a size bigger?
 

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QUOTE (upon2passingyou @ Mar 29 2010, 09:21 PM) index.php?act=findpost&pid=846691
Same size bore, 60mm stroke. I believe the head has a few extra bolts more than the yfz's 4 main head bolts and 2 side nuts. I believe the 426 has a manual mechanical decompression system that isnt integrated into the exhaust cam but im not positive. Working on this motor will be basically the same as working on a yfz motor, yzf motor, wr motor, and even yz/wr250f motors. You wont have any trouble working on this motor.[/b]
Pretty much got it all there. The cylinder and head bolt patterns are a bit different. Cases are smaller, exhaust cam doesnt have the decompression system.
 

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I have a 04 YFZ 450 and I blew that head I have a new head from an 05 yz426 everything worked out good until I went to put the timing chain on it is too small do I need the timing chain from the 426 because because the 426 head is a little thicker than the 450 head? Also oil tube too short
 
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