Wear on XR4 cam lobe

The - most probably very first - sparkplug change on my '03 XR4 required taking the head off, as the plug broke into the head - we have tried everything to get it moving, but it did not budge, just broke into 2. The thread was renewed, it's fine now, but inspecting around revealed the cam does show some ugly wear on one of the lobes.


The engine runs and sounds great, valves, rockers and other parts of the cam are like new, engine has 8K kms on it.

Should I worry, can a machine shop do something about this, or start thinking about a new cam sooner or later? Or just ride it and worry about something else.

Thanks for the help fellows.

The pitting/erosion that you are seeing is the hard surface flaking off the cam lobe. The situation will only get worse. Take a good look at the rocker arm for that lobe, it might be damaged as well.

Having a machine shop weld it and resurface it might cost as much or close to a new cam, so a new cam might be the way to go. And I agree with Creeky, take a good look at the rocker for that lobe.

You are best off when you replace cam,always replace rockers.Nobody likes to take it apart the second time.

Thanks for the prompt replies. The rocker is in mint condition, there is no visible damage on it now.

So I'm looking to get a new cam :smirk: The engine is stock, I'm happy with its performance, should I consider getting a hot cam (I can live without the autodecomp) or just stick with a stock one?

And, can I put a few hundred kms in this cam without constant worrying? As I've written it was just discovered by coincidence.

Yes you can ride it ,but if your rockers are still perfect.Then I would get the new stock cam,before you ruin your perfect rockers.

I took the cam to a respected Honda service with racing background, they think the valve on that lobe was set too tight, there's a small "ring" wear on the cam in that position. And that meant extra stress/heat for the lobe, resulting in rapid wear of the hardened surface.

This correlates somewhat with my first valve adjustment on this bike half a year ago, when I found the PO set one of the valves very tight - can't remember now which one...

They advised to carefully polish the positive irregularities if any, and the oil will help to fill up the small holes.

I'm a bit skeptical, and still think a new cam would be the long term solution.

Your thoughts please?

Stock cams seem to be around 200$, stage 1 hotcams are 130$, so I'm aiming for the latter.

I would replace the cam.

I've put together the bike with the old cam, can't miss 1+ weeks of riding waiting for the new cam to arrive here in Hungary. The engine runs and sounds great, as before.

I'm just about to order the new cam. If any of you has any objections for using a stage 1 hotcam, please advise during the weekend. I'm fine without the autodecomp.

Thank you guys.

You are best off when you replace cam,always replace rockers.Nobody likes to take it apart the second time.

I want to reiterate this point. The cam and rockers wear as a set. Even if the rockers look good the wear surface is not flat anymore. The new cam will accelerate wear on the high spots.

An update on this thread: I've put in a stage 1 hotcam, and it works great :ride:

I was expecting more pull in mid and high revs, which I've got, mildly noticeable but it's there, and even "lugging ability" in low rpms is improved. I was not really looking for more power, but the bike just got better to ride.

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