Rocker arm And Cam Wear

i am working on my buddys 1993 XR 650 L. It had a ticking sound coming from the valve train so we adjusted the valve clearance and the sound was still there. Then on the next ride it started backfiring on decel. We checked the valve Clearance again and found it was still normal. We decided to pull the valve cover today and found the rocker arm and cam lobe for the right side exaust valve was worn. The other exaust rocker had some ware but not as much. What would cause this?? Im going to replace the cam and rockers but am worried about it happening again if there is an oil problem.

Hi, have the same problem on my '90 xr600r.Dont know what caused it.Please let me know in case you find the reason. I will do the same if I find it first.

Thanks, Lars

I've never had any wear on any of the 6 XRs I've had, two of them had high miles, but I run Mobil 1 Gold Cap Synthetic, jet the engine slightly on the rich side, run free flowing exhaust systems, set the valve clearance on the loose side of the specs and check the downtube screen once a year. You may want to check the oil pressure and make sure the engine temp is normal, lean jetting runs hotter, regular oils break down at lower temps than syn oils, tight rocker setting generate more heat on the lobes.

Only XR engine I've had experience with that had unusual cam and rocker arm wear wasn't getting frequent enough oil changes or valve adjustments (I strongly suspected old oil to be the biggest contributing factor).

The RH exhaust valve is the one operated by the auto decompressor, I would suspect a problem in this area.

been there done that.......

When adjusting the valves, the manual stresses not to have the engine back spin at all or the kick-back decompressor will open the valve slightly. It causes a false adjustment and when the lobe has the rocker running tight, the cooling oil is all wiped away and then loses the hard surfacing.:devil: A replacement hot-cam manual also says to run 2 thou. looser tolerance as well. After rebuilding mine, I had a too lean condition that (I believe) dropped the exhaust seat on the same valve and had to get it re-installed and staked so it won't happen again. It may all be related but I now triple check my valves after adjusting to be SURE the specs are right.

thanks for the info now i guess its time to replace the cam & rockers. Where is a good place to buy parts for the XR650L i have seen the cam a few different places but where can i get the rockers?? thanks for the help!!!!

Very similar thing happened to my 01 650R last month. Thought the valves were out of adjust ment, but it turned out the rockers (mostly the intake) were wearing out on the cam side. Look closely at the top of the valve stems to see if they need to be replaced. Check out this place for a good price on new parts, it will still be painful, though. My total bill has been about $260 so far.

I still haven't figured out if it was lack of oil, valve lash too tight, or temperatures. Although I am assuming it was oil. I might go to Synthetic after this. Good Luck!


My old XR 600R had significant wear, when I pulled it down to put in a hotter cam. I switched to synthetic (Amsoil 20W-50). It seemed to run a lot cooler, even with the high comp piston....I've been a believer in synthetics ever since. Expensive oil changes, but the alternative is a lot more!

thanks for the info now i guess its time to replace the cam & rockers. Where is a good place to buy parts for the XR650L i have seen the cam a few different places but where can i get the rockers?? thanks for the help!!!!

XRs only?

I picked up a '99 XR 650 L with 2,500 miles this summer and after riding another 1,000 miles I had the same problem. I changed the oil and filter when I got it and all was good. At 3,700 miles I replaced the cam, all four rockers and bearings. I also changed the oil, flushed downtube and crankcase with oil and checked the screen on the down tube. $280.00 latter was on the road. After 300 miles the same thing occured. After replacing the cam etc. I ran the bike with the valve adjuster caps off and it looked like it was getting plenty of oil. I have the valve cover off now and will take the right side cover off and check the screen and oil pump. I think the bike sat a long time because of the two cups of water in the gas tank. Any good XR mechanics in or around Salt Lake City? :mad:

You can check your oil pump flow by loosening the top oil pipe bolt a turn or so. Start the bike and oil should leak out when the pressure builds up. It's an easy way to verify that some oil is getting to the head.

I have heard that the big aircooled XRs dont like to be idled? Something to do with the fact that one of the rockers doesnt get much oil?

(If I can find something more I will.)

i also have a 93 XR650L. i posted a similiar question on low rpm ticking, but now that you mention it, when i unwrapp the throttle i get a few pops out the back also. it's definetly time to crack it open and check things out. this is a great place for info.

I am getting some oil to the top end, how do you tell if the oil pump needs to be replaced?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now