Factory valve clearances too tight- is this typical?

[Fuzzlewump]

I've just finished putting my cylinders back together after installing new gaskets and seals, cleaning up all the carbon deposits, etc. (A massive thank you to Sunburned and Rick!)

It didn't look like anyone had ever been inside the engine since it left the factory. Bike has 14,000 miles.

Everything looked pretty good in there, but when I checked my valve clearances I found something strange: on all of my valves, the clearances are tighter than the manual calls for.

Haynes says intake valves should be a minimum of 0.11mm- mine come up 0.08 on the front and 0.06 on the rear. Exhaust valves are supposed to be a minimum of 0.16mm - mine come up 0.13mm on all, except for the left valve on the front cylinder, which comes to 0.10mm.

Are these numbers OK or should I put thinner shims in? How could stock clearance specs be tighter than the book calls for? Could these tight clearances be responsible for my inability to tune the carbs?

[Jimustanguitar]

It's not uncommon for valve lash to tighten. You should re-shim it back into spec. It'll never be easier to do than it is right now.

It's especially important to adjust valves when they're too tight. As things heat up and expand, you could get a valve that doesn't seat properly.

[QBS]

Consider adjusting them a hair looser than stock.  Others may wish to comment.

[Jimustanguitar]

Consider adjusting them a hair looser than stock.  Others may wish to comment.

You might have to make them looser than stock because you can't just buy a %$@# metric feeler gauge anywhere :)

[Cdnlouie]

Hey Fuzzlewump, I will mention that if you are not very familiar with doing valve clearances there is a strong tendency to under-read the actual clearance.  If you are an experienced valve adjuster (and know what I am talking about) then I would go ahead and do an adjustment.  When you do a valve clearance you should have a strong pull on the feeler gauges and not merely be able to pass the gauge easily under the cam lobe.  In other words, it should be a bit difficult to get the feeler gauge under the lobe, but if you can squeeze it under and pull it out,, then that is closer to the actual clearance.  Of course this should be done with a cold engine and with the lobes at their proper adjustment position.  Make sure you don't have the cams coming into engagement and thus decreasing the reading.  That one exhaust valve sounds at least deserving of attention.  This would not likely affect tuning as long as there is some clearance.  You are right to wonder about this, because that would not be good Japanese quality control.  Usually a valve adjustment at that mileage would involve maybe one or two shims at most, and most of the time none.

P.S. Jim, one of the advantages of being Canadian is we have ample supply of metric feeler gauges. We got with the program a long time ago (LOL).

[vintage bikeworks]

What you've described for a bike with 14,000 miles which you think has never had a valve adjustment is normal.  As the valves seat during initial break in and subsequent miles (km), the clearance will decrease.  (Valves settle into the valve seat which decreases clearance between valve stem tip and lifter) Keep in mind that the factory clearances are specified to take into account changes when the engine is up to operating temperature.  I would suspect actual running clearances are less.  This is why you will always see higher specified clearances on the exhaust valve since it is exposed to more heat.  You may see an improvement in engine running due to the valve adjustment.  What you are doing is step 1 of getting the bike to run as it should.  You'll need to follow up with good clean carbs and carb sync.  Sync will almost certainly change due to the change in valve adjustment. 

For the valve adjustment newbie, I would suggest practicing with three feeler gauges... One size under, one the correct clearance and one size over.  In this way, you will develop a "feel" for the gauge thickness.  The oversize will be very tight or not fit, the undersize gauge will be loose and the right gauge will have the correct "drag" or "feel" when used.   Soon, you'll develop the feel for the correct thickness. 

[Fuzzlewump]

Thanks everyone for the advice! I'm going to spend this evening hunting down the appropriate shims and making the necessary adjustments.

I did as Vintage has suggested and tried three sizes of feeler gauge. It was difficult to find metric gauges that read in detail....mine are made in sizes that skip over some numbers. I obtained my readings by starting low and working my way up until I found the first gauge that will slide under the lobe. If the gauge above it feels too loose and the one below won't fit at all, that's the one I mark down.

The weather is cooling off down here....riding season is about to kick off! I can't wait to get this baby back on the road. A buddy has been letting me use his CBR600 to get around town and it's a great bike, but I'm really starting to miss the feel of my V.

[Rikugun]

Even with metric thickness gages the process can be a bit of a judgement call at times.  A complete set of either SAE or metric will get the job done. I too use a range of gages in the spec range and beyond (on both extremes) to really confirm where the clearance is.

When using smaller sized gages, rather than pushing the gage through when it's relatively tight, try putting it under the cam alongside the lobe. Then pull it out at an angle towards the lobe's centerline. This has the effect of dragging it under the lobe and is more effective then having it fold as it's pushed. This works very well with screw tappets as well. If it's too tight you can get the gage wedged in there pretty good so use caution.  ;)

[Fuzzlewump]

When using smaller sized gages, rather than pushing the gage through when it's relatively tight, try putting it under the cam alongside the lobe. Then pull it out at an angle towards the lobe's centerline. This has the effect of dragging it under the lobe and is more effective then having it fold as it's pushed. This works very well with screw tappets as well. If it's too tight you can get the gage wedged in there pretty good so use caution.  ;)

This is a great idea, and I'm gonna remember it when I go to measure clearances after the new shims are installed.

I called around a bit and found a great mechanic who had the shims I needed. Between talking to him and you guys on the forum I've gained confidence that the job is going well and I haven't seriously messed anything up, lol! I've also learned that the valve adjustment was indeed greatly needed, and almost certainly is the main culprit for my carb tuning problems.

The best part of this particular job is that it's the only integral part of the restoration that I haven't yet completed. By the time it's all put back together and tuned I should have no more major work for a long while.

[fret not]

When you change valve shims make sure there is NO dust, dirt, fuzz, debris, or ANY other foreign matter between the shims and the bucket (or anywhere else) or it can cause a feeler gauge reading that is not accurate.  It is best to be as scrupulously clean as you can manage.