One ugly lobe

[T Legg]

Ian and I were adjusting the valves on his ZZR1200 tonight and we found one damaged intake lobe on the camshaft.The bike has been running smooth and strong before even though we found several out of spec tight valves when checking.The valves are shim over bucket like our fj's but they have what I guess you would call a rocker arm that rides between the cam lobe and the shim.There is no obvious damage to the rocker arm or shim so we assume the lobe damage is old.Our thoughts are to leave the lobe alone and not remove any more metal,we figured with the valves adjusted correctly it will only run better than it did and he could live with the bad lobe.We would love to hear the opinion of others

[Motofun]

At the very least I would make sure there is no proud metal.  The cam lobes are bearing surfaces.  With the reduced surface for bearing the load the contact pressure will increase.  Too much to cause further damage is the question.  The higher contact pressure will disturb the oil film and probably cause failure but I'm guessing.  How much do you trust your luck?

[ribbert]

Internet diagnosis is hard at the best of times, even with lots of info, but this question needs a photo.

Much depends on the nature of the damage but you say the mating rocker arm shows no marks, that would suggest it's old. It would be most likely that the rocker arm face would have matching wear if it was current.
Everything Motofun said I agree with, but once again, depends on the extent of the damage.

Take a photo, button it up, ride it, compare it to the photo next oil change and look for any sign of increased wear. My gut feel says it's probably nothing to worry about.

Noel

[Motofun]

Upon looking at the picture again, it appears that the surface problems are opposite the cam lobe.  If true, that surface should not be in contact with the shim though it might ride on the finger follower.  As long as it's "free" and it is smooth you should be OK.  The real stress occurs when the lobe pushes against the shim with the cam lobe.

[FJ_Hooligan]

As Noel said, monitor the lobe for additional wear.

If the cams are surface hardened then there's a chance the wear could break through that surface and degradation of the lobe will accelerate.

[T Legg]

unfortunately the damage is on the cam lobe. his cam lobes are somewhat rounded(not worn) in shape than most of i have seen.We are going to recheck if there is galled metal attached to the cam lobe and if not take Noel's advice and reinspect it in a couple thousand miles for further damage.Meanwhile my son will start looking for aftermarket cams,probably about 900.00 dollars for a set.

[JMR]

 An aside.....use ZDDP additive with rocker arm engines....it helps. I do a lot of work on SOHC CB750's and have used many performance cams....they need extra zinc.

[Pat Conlon]

Mike, do you think that cam lobe can be repaired? Hardwelded?

[Tuned forks]

Travis, the news is bad.  That lobe looks as if it has worn thru the induction hardness on the surface.  Further deterioration will spread metal shavings into your oiling system and onto your crank and rod bearings.  Ask me how I know buddy.  I think either Randy or Robert should weigh in on this with their opinions before you do anything though.  Good luck it Ian.

Joe

[T Legg]

We went back and examined the cam lobe and rocker .the rocker arm of the bad lobe looks better than many of the other rockers you can see it in the picture I took.Ian has had this bike for about 8,000 miles and the previous owner had a list of work he said had been done and he never mentioned a valve adjustment,so if it was old damage it hasn't hurt the rocker arm much.when looking at the lobe there is no deposited metal or high spots it is deterioration of the lobe.other lobes show some pitting but nowhere near as bad.they seem to be poor quality metal cams.

[Troyskie]

As others have said, the damage looks old. Looks to me like it was run out of oil, or absolutely hammered while stone cold.

If you've not found any metal shavings in the oil plug magnet (does it have one?) it certainly hasn't been filing itself away. If you still have the old oil put a magnet in it to see what you find.

Have you considered what shim you replaced might change the clearance and cause the degraded non hardened surface to contact the rocker?

Overall, if it was mine, I'd replace ASAP if funds permitted.

[ribbert]

OK, now we have the photo. Forget everything I said yesterday, I would not ride that around the block! While it's difficult to gauge the depth of the damage from the photo, in my opinion it is beyond serviceable.
The lobe to the left of the one in question, in the bottom photo, appears to be not far behind the damaged one!











It's interesting to note the marks on the adjacent lobes, they appear to be heat effected in the centres, maybe they're next? Have you checked out any Kwaka forums to see if this is a common failure?
Second hand camshafts shouldn't be that expensive, they probably used them in a lot of engines.

If the cam lobes are more rounded than you are familiar with, it's likely it has offset rockers, which increases the travel on the valve side.

Who knows with second hand bikes, maybe a previous owner tried to hand grind a shim or it suffered some sort of lubrication or over heating event in it's past, maybe it's worn out...... how many miles has the bike done?

Noel

[ribbert]

Geeez, what happened there? I only copied the photo address from your post??  Anyway, that is the lobe I was referring to.

Noel

[CutterBill]

Now you know why the PO sold it. As Noel said, the cams are shot; replace. Don't forget that you must also replace the cam followers (rocker arms.)  Worn followers will quickly wear out a new cam.
Bill

[T Legg]

Ian has posted on a ZZR 1200 sight.They are not as helpful as our forum,but they did say that this is very common and .they call it camshaft herpes.apparently many have ridden on with the problem,but I don't see many ZZR's on the road.Ian's bike has just under 30,000 miles on it.I think the original cams on these bikes were poorly made,the heads also have a problem with porosity of the metal causing coolant to weep through to the outside filling one of the spark plug wells with coolant.these problems may be why the bike only had a two year run.a used set of cams may have the same problems.a site with after market cams requires the original rockers to be hardened at 35.00 dollars each special springs and retainers.all of that approaches what he paid for the bike,2500.It is a nice riding bike,it handles well for a big heavy bike and on the open highway it will walk away from even the faster of my two fj's,but Ian is going to have to decide how much he loves his bike.a used Zzr1400 goes for around 5500-6000 and might be a better deal,he is too tall at six foot five to be comfortable on my FJ's.