valve adjustment surprise

[DeanR]

Just measured valve clearances for the first time. I don't have metric on my feeler gauge but here they are converted.
All rearward valves (exhaust?) measure .0015 in./.0381mm...
Forward valves (intake?) #2 & 3 also .0015 in.
#1 is .003in/.0762mm..... # 4 is .005in/.127m
These are WAY LOWER than spec. Caught me by surprise because the bike runs so well. I was basically just checking to learn about my bike and to put a different valve cover on. Would much appreciate some insight from you guys. Thanks so much.

[John]

Laxdad, the best way to take the measurement is with a dedicated metric feeler gauge. I tried to use a combo standard/metric feeler gauge, but it just wasn't accurate enough. I had to buy one off the Matco tools truck. It made a world of difference.

[DeanR]

But why are my clearances just about non-existent? Does't seem that another gauge would make That Much difference. Am I right about which valves are exhaust/intake?

[TopCatGr58]

Hey Dean,

When you say forward, if you mean the front of the engine, then they are Exhaust not intake, and the Rearward ones are the Intake not Exhaust. However like you said, they are all appearing too close.

Question, did you do the measurements while the engine was still warm from after being run? If so, then the parts may have been slightly expanded from the heat. Try rechecking them after it has had several hours to cool.

The manual quotes the specs in inches and metric. I would think that if you have a good quality set of gauges, you should be able to get accurate measurements with them. Did you spin the engine/cams slightly to ensure that you were on the lowest side portion of the cam lobes?? Also folks have stated that sometimes there can be too much oil between the shim and the lifter cup, causing smaller than normal clearance measurements, so the say to rotate the engine over by hand several times to help squeeze out the excess oil and then recheck the measurements.

Then after all this, if they are still too small, then looks like you'll be needing to adjust/replace some shims!
T.C.

[DeanR]

Hi TC,
Did everything that you mention. Cold engine, turning the engine in small increments and entirely around a couple times. Are valves very often off by this much and is it indicative of a problem or just that they haven't been attended to for a long time.
Dean

[TopCatGr58]

Dean,

You would think that with the friction of the cam lobes against the shims that the clearances would increase, however "they" state that over time the valves can recess/seat further into the head/valve seats, which pushes the valve stem closer to the cams, thereby shortening the clearance.....so it's just a matter of replacing shims to regain the proper clearances!

I drove my XS11 for some 9 years without any valve adjustments being done back in my ignorance years!! Then after replacing a few valves, lapping all of them, I only needed to replace a few of the shims....swapped others amongst the cylinders, so it's not uncommon for these engines to remain fairly stable for years.
T.C.

[prometheus578]

Dean... many times at work I have older bikes with NO clearance at all. In fact... the cam is actually holding the valve open a little. Had one last week. Did a compression check... readings were a little loopy. Adjusted the valves, and rechecked the compression. Compression values rose back up to where they should have been.