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Burning Oil - What A Shame

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So my XR650R is burning oil. I knew this when I boughht it but I did not realize how much it was burning - about a full quart every 150 miles. The top end is also making a pretty good clatter even after I adjusted the valves twice (they were never out of spec) so I figure the cam and rockers are worn.

 

It looks like I gotta do a top end rebuild - while I'm in there I figure I might as well add some goodies.

 

Originally I was planning on an 11:1 stock bore piston (if my bore is good) with an HRC copy cam and hardfaced rockers. New valves and guides. But then I got to doing some reading and it seems that the higher compression piston and cam take away from the low end. The below graph is supposedly stock uncorked vs. HCR "kit":

 

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I am a big fan of low end power. I don't want to loose any - If I have to, I'll just do a stock rebuild to keep my low end.

 

But if I used the above outlined parts with a little bigger bore (102mm), would it keep my low end as good as stock?

 

Also, what are we doing for cam chain parts these days? Just running stock and not worrying about it?

Edited by 1972RedNeck

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putting a igh comp 11.25-1  JE piston and megacycle cam in my bike took nothing away from the bottom end torque,if anything it has moregrunt from the high comp piston...

 

And having more mid range and high rpm power is freekin nice when I pass cars on the highway..

 

B

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putting a igh comp 11.25-1  JE piston and megacycle cam in my bike took nothing away from the bottom end torque,if anything it has moregrunt from the high comp piston...

 

And having more mid range and high rpm power is freekin nice when I pass cars on the highway..

 

B

 

Is that from the stock 100mm bore with 8.5ish compresion to your current 102mm? I was kinda thinking that an overbore would keep the low end... Any firsthand experience on an R?

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That curve looks like the low end (on hopped up engine) was shifted over only approx 200 rpms.

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That curve looks like the low end (on hopped up engine) was shifted over only approx 200 rpms.

 

Yup - and I think a 102mm piston might be able to shift it up by 2 to 3 ft lbs.

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Is that from the stock 100mm bore with 8.5ish compresion to your current 102mm? I was kinda thinking that an overbore would keep the low end... Any firsthand experience on an R?

 

 

That was from a 1001mm JE XR600R piston and also my current setup........

 

 

Doesn`t matter if it`s the XRR or XRL....... you`llget the same results unless you go with a full race cam......the cam is the key..go up just one step over stock and you`ll not loose any low end torque,and what you did lose a high comp piston will bring back......

 

That curve shows a shift of a few hundred rpm which you would never notice on the low end,but a marked improvement on the top end where these engines lack.......I`d be all over that kind of improvement..

 

B

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Following this as myn is starting to burn oil and im down to 120psi.bike has 15000ks on it.

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