Slight miss

[Jeff0308]

For a while now I've been noticing a slight miss like a tight / burnt valve just above idle. It's ever so slight but I notice it more when I've got my helmut on and I just go slightly above idle. Seems to smooth out however it doesn't appear to effect the running other than its uneasy idle. Thought maybe burning valve runs to smooth and last compression test was minimal difference. Not certain when shims were done last. What's the engine characteristics of shims requiring attention?

[Pat Conlon]

Over time the valves get tight. This happens as the valves recede on the valve seats causing the shim/cam clearance to get smaller.
If left alone and not adjusted, the valves will not seat causing a loss of compression.

This will cause a loss of power. The bike will not pull strongly. The FJ's have an abundance of torque so on our bikes you can lose some and not notice.
This loss is gradual and gets progressively worse, when riding on the street many owners don't notice it right away until damage done to the valves and seats.

Check your valve clearances. If tight, fix them.

That said, I don't this is causing your slight miss, especially if your (hot) compression tested fine.

[oldktmdude]

   Jeff, the first thing I'd check is the spark plugs. They can often misfire at lower revs and then smooth out as revs increase. It's also easy and cheap to do. Check the simple things first.  Pete.

[FJ_Hooligan]

What do the plugs look like?

If one or more are black then it might be as simple as replacing the O-rings on the carb needle seats.

Also, Pete has a good point.  A cracked plug will cause a low RPM miss.

[Jeff0308]

Plugs are realatively new. Done about 2000km. However I haven't removed them since to check. That's next. Might do it with valve shim check. Or sooner