XR650L Compression Hight

3 replies to this topic
  • Ryanthegreat1

Posted August 31, 2007 - 06:19 AM


Hey guys not sure if this has been covered or not but I just picked up a new JE piston from Xr's Only spec'ed at 103mm 10.5:1 and...

I have a question about its compression hight. When compared to the piston that came out of the bike (Wiesco 102.4mm 10.25:1) the new piston has the wrist pin about 3 mm lower in the piston than the old.

Now I know that the XR600 had a shorter stroke with a taller compression height and the XR650L gained its stroke by moving the pin in the piston closer to the dome. Is it possible that I have a piston for the XR600 and if I do will that 3mm of extra height cause the piston to make contact with the head.

I would check this myself but to really see where everything is going to sit I will need to get it all assembled and that includes a bore. :(

If I have confused everyone I will try to get some pictures later today.

  • martinfan30

Posted August 31, 2007 - 06:55 AM


give xr's only a call.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • machman

Posted September 15, 2007 - 02:52 PM


I bought one of their JE 10.5:1 101mm pistons from them through e-bay for my XRL. I checked the part number on the JE website and it is indeed for the XR600R not the XRL. From what I researched, the effective compression of these pistons in the XRL is lowered. For me, I'm looking at 9.5:1 compression, not the 10.5:1 I was hoping for.

Prove me wrong please, but this is what my research has told me. I'll look at my older posts to verify.

  • machman

Posted September 15, 2007 - 02:58 PM


I just checked my JE against the stocker. The distance between pin and piston top is the same. The only difference between mine is that the stocker is concave and the JE is flat withd divots for the valves.

...I'm now thinking the compression will be the same!

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