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bluerock5

XR650L: Valve Adjusting, does the L have a decompression system?

7 posts in this topic

I'm going to adjust the valves for the 1st time by myself and in reading in the Clymer manual on page 57 it mentions that both the 650R and the 650L have a decompression system and that you have to adjust the right hand exhaust valve differently. Is this true? I'll take any tips you have for adjusting the valves. What's a good feeler gauge to use, Thanks

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Just approach TDC by turning ccw, and DON'T turn cw if you go too far.

I purchased a small two sided feeler gauge from my local Honda shop with 0.004 and 0.005 on the ends. Of course, I chucked the packaging and don't remember what brand it was :cry: , but the feelers are only about 0.25" x 0.4" square and angled, which allows you to actually get them in and angled at the correct angle to check the gap. The gap is not orthogonal to the axis of the adjustment screw, but slightly cocked towards the side of the bike.

The intakes took the 4 and the exhausts took the 5. The Honda manual makes no mention of a difference for the right side.

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Answering the original question, yes the XR650L has a decompressor... it's an automatic one. The XR600R also has a manual one. The auto decompressor will slightly open the RH exhaust valve at cranking speeds to lower the compression and make it easier for the starter motor to crank the engine. If you are turning the crank CCW with the nut on the end of it, you can hear a CLICK as it approaches TDC. That CLICK is the autodecompressor releasing the RH exhaust valve.

I too use the Motion Pro feeler guages, they really make the job much easier!

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Motion Pro is the brand. The intake and exhaust valves are set with their specifed lash or clearance, IN: .004" EX: .005", no difference between the right or left exhaust. valves.

The bike needs to be dead cold and remove the spark plug to make it easier to reach TDC. When rotating the crankshaft CCW, make sure as you are approaching TDC mark on the flywheel that you don't over-rotate. If you do go past TDC, do it again. You can watch the intake valves open and close so you know you are heading towards TDC on the compression stroke.

Check the clearance before you adjust the lash, when you snug the adjusting nut, after you torque the adjusting nut and one more time before you put the valve cover caps back on. The gauge should have slight resistance on it, but not too sloppy or too tight. Also, get some additional strip-type gauges to do the go- no-go method with one size smaller and one size larger to verify each gap is correct. You don't want the clearance to be too minimal (tight). Remember, a loose valve is a happy valve.

Happy adjusting.

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