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Discussion Starter · #1 ·
Okay, so in Hatfield as some of you know my machine started eating oil, by eating I mean about 8 ounces every 30 minutes. So after a engine breakdown, it was noted that the compression rings were fine, but the oil ring was sharp around the edges. Also, all four valves were pretty wore, and it looks like I am going to need a new crank as well. Possibly due to it running low on oil the two times I was down there. It could be saved, w/ the top part being honed out a little bit, but I am going to play it safe and just get the new $500 dollar crank. Getting 4 new valves as well, looks like the valve seats are still in great condition, but gonna clean them up. I'm getting the 730 kit from thumper racing along with a stage 2 cam, not sure whether I am going to do Hotcams or ThumperRacing cam yet, depends if theirs is a drop in as well. Well the engine is completely apart, I may even get the Matlock Clutch to put in there. Anyone else think of anything I should do as well? I mean I'm already around $1500 or so in it, so might as well go all out right?
 

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If you have to replace the valves might as well put XR650R intake valves in it, they are 37mm instead of 36mm. Get a good valve job and youl be good. 730, thats still funny when I hear it lol. If it was me I would go with a good port job and cam before I considered making the engine larger with a poor flowing stock cylinder head.
 

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Discussion Starter · #3 ·
Im getting it ported and a stage 2 cam as well. Why would it be poor flowing? I'm just curious, engines aren't my fortay.
 

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making the engine larger with a poor flowing stock cylinder head.
What I mean by this statement is increasing the engines size will put more demand on the camshaft and cylinder head to feed it with airflow and fuel. The stock XX cylinder head does a poor job of doing this for a 686cc engine so going to a 727cc engine will only make the effeciency of the stock cylinder head look worse. Since you have stated now that the cylinder head will be ported then it sounds more like a better running combination. This thread will help you understand the importance of effecient airflow to a performance engine:

http://www.club700xx.com/vb/showthread.php?t=4328
 
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