Checked valves... Blued spot on #1 intake cam?

Like it says... the tip of the cam lobe looks like it has been blued by heat slightly compared to the other cam lobes. The clearance on it was .006" and the valve shim did not look damaged. The plug for #1 looked clean, which I think means it's running lean? The bolt hole for the valve cover was stripped so I cannot check to see what shim is in it, but at .006" clearance I think it is within spec... correct? Should I be worried about the cam? Unfortunately I won't be able to get pics of it for a couple of days.

 

First off, you can always use the "zip tie trick" http://xjbikes.com/Forums/viewtopic/t=29209.html if you can't use the tool because of a stripped out bolt hole.

.006" is NOT REALLY in spec; this is why I always recommend a "metric" feeler gauge.

Spec is .11mm~.15mm. .006" is actually .15240mm, which means it's a tad loose. Odd.

Loose not good, and could indicate an issue with that valve (or an incompetent PO.) How many miles on the bike?

 

my guess is the last time the valves were adjusted that one was tight and that was the closet shim he had As long as the lobe is not rounded or flaking it should be ok. Without pulling the cam and measuring the lobe there is no real way of checking it.Something else that will vary a little person to person is how much resistance that.006 was if it was a tight fit should be fine. Metric is the way to go with measurements. every valve i check i will try the next thicker guage in it if you can force it in your gonna be a bit on the loose side of your measurement. personally i would rather be on the looser side then the tighter side of specs

 

Since it's a #1 lobe you're concerned about, pulling the cam wouldn't be necessary to measure the lobe.

The factory book has the specs and tolerances for the cam dimensions; not a bad thought...

 

Pics would be good - then we can see whether it is truly a heat discoloration. The measurement on that valve should be fine at .006 - I sure wouldn't worry about that. A much bigger concern is the plug color.

If that cylinder is running lean then that could be the reason for the heat. You will want to address that before you burn up a valve or a piston.

What else can you tell us about the bike; mileage, original airbox or has it been switched to pods or a K&N, original exhaust or switched to a 4/1 ... stuff like that will help us help you in a diagnosis.

 

Let me add one more thing here. Even if the cam lobe is slightly discolored from heat, as long as you correct the issue that caused the heat I wouldn't worry about that discoloration. A cam can turn blue before you will lose any appreciable hardness. The bigger concern would be compression. Check your compression and if is compares favorably with the other cylinders I would put the beast back together, correct the lean condition, and ride the heck out of it. When you check your valve adjustment at the next interval you can reevaluate the cam lobe. Until then don't worry - be happy.

 

I do need to get a metric feeler gauge. I didn't really want to wait for one to come in the mail, so I went ahead and gave it a shot the way it was. When I was measuring the gaps I always tried the next bigger gauge just in case. .0065" didn't fit. I also managed to lose my factory manual somewhere during my move. I am gonna search for it at my parents' place this weekend.

The bike has stock airbox and exhaust. The airbox did crack a little bit around the #1 carb-to-airbox boot. It's got 29,900 miles. I have ridden it less than 2 miles since I picked it up... Don't have a license yet and have been trying to get it all checked out before I get it on the road.

I haven't run compression tests on it yet because I wanted to make sure the valves were adjusted correctly first. The other intake valves are all around .004-.0045" and the exhaust valves are between .006" and .008".

I can get pictures for y'all on Thursday. There didn't seem to be any extra wear on the lobe, just the coloration. I thought that the lean condition would be more likely to burn up the exhaust valve than the intake valve though?