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heavyhitter

Gear heads help me out

6 posts in this topic

Looking for intake and exhaust lift and duration on xr650l and xr600r STOCK cams.

FYI I am adding a 1mm overbore hi comp piston and possibly a new cam. From what I have read on various site is that OEM cams last much longer. So I am thinking of adding a 600 cam to my L.

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Don't know the figures, but a 600R cam will be a bit better than a 650L cam. Probably less than a hotcams stage-2, though.

Dave

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I noticed that the XR650R Hotcams Stage 1 & 2 have a pointy lobe geometry compared to the Stock Honda and HRC cams. This makes the acceleration of the rocker/valve assembly higher and may contribute to premature valvetrain/cam wear.

The HRC cam has an asymmetrical lobe that opens the valve fast with a short ramp from full close to full lift and closes it slower with a longer ramp from full lift to full close.

The Hotcams Stage 1 & 2 for the 650R has short ramps for both.

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I talked to the guys at XR's Only a week or two ago and they've stopped recommending the HotCam for the XRL. Apparently there have been oiling problems with it and it's burning rockers or something.

With that said I still ordered one. Although XR's Only is an incredible resource one must keep in mind that when they give advice it's generally from their experience with engines that are tuned to run at max speed and max HP in high heat environments for extended periods of time. For wheelie-ing back and forth to work putting 4000kms a year on, I'm not too worried.

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