After disassembly the next step is to measure valve clearances. This was surprisingly easy just following the procedure in the Clymer manual, although there are 5 valves per cylinder for a total of 20. Why so many?
Unfortunately my tapered feeler gauges are at 0.03mm intervals so it wasn't always possible to tell exactly what the clearance was, but easy enough to tell if a valve was significantly off. With the cams at the proper position, insert the feeler gauge that is one below spec. Hopefully that slides in easily. Then slide in the gauge that is in the middle of spec. Hopefully that goes in with a slight amount of friction. Then insert then next larger gauge that is slightly thicker than spec. With my feeler gauge set the gauge larger than spec shouldn't go in at all. The clearance specs are:
Intake: 0.11 - 0.20
Exhaust: 0.21 - 0.25mm
Using this technique I determined that all the exhaust valves were too tight, and all the intake valves were tighter than I'd like, but technically within tolerance. Unfortunately this meant there would be no question about removing cams. But I knew that.
Following the Clymer manual procedure I removed the cams with the sprockets attached, after making white-out marks on the cam chain and sprockets so I'd be able to reassemble them without changing the engine timing. That made sense to me because that's how the Bandit and SV650 cams are removed. The procedure calls for first removing the cam chain tensioner and gasket after removing its cap and winding it so it stops putting pressure on the cam chain. Then tying up the cam chain with wire so it doesn't fall into the engine. Next removing the cam holders by loosening the bolts in stages, in a criss-cross pattern starting from the outside. Finally removing the cams. Unfortunately removing cams with sprockets attached was a mistake as I found out later. In the meantime I was able to pull the buckets with a stick magnet and check the shim size.
Cams pulled with sprockets attached, cam caps, and a fly
Cams removed showing tops of the buckets
Pulling buckets with magnet
Note: The correct procedure for removing cams involves positioning the engine at TDC on the exhaust stroke ("H" mark aligned with mark on frame), removing cam sprocket bolts, then turning the engine back to TDC on the compression stroke ("T" mark aligned with mark on frame, cam lobes pointed away from each other), then removing the remaining cam bolts. Finally removing the tensioner and the cam holders.
The cam holders are marked, so if one is familiar with the markings they won't get mixed up even if they're not stored in the proper position. The buckets, however, belong to a specific valve and must stay with that valve. So it was important to carefully store all the parts in order. The buckets are not labeled and have no distinguishing features.
Exhaust valve buckets, in order, with their shims
Here are the valve clearances and the exhaust valve shim sizes I found underneath the buckets.
Valve clearances
Shim Math
After pulling shims it's necessary to determine what shim sizes are needed to set the valves back within specification. From the Clymer manual the formula is:
New_shim = (measured_clearance - spec) + old_shim_thickness
So, if I want to set an exhaust valve to the middle of spec, 0.23mm, my measured clearance is 0.15mm, and the old shim thickness was 1.85mm, the new shim would be:
(0.15 - 0.23) + 1.85
Resulting in a new shim measuring 1.77mm.
Unfortunately aftermarket shims come in increments of 0.05mm, so my available options would be 1.75 or 1.80. More math:
1.80 = (0.15 - x ) + 1.85 1.80 = 2.00 - x 1.80 + x = 2.00 0.20 = x
1.80 won't work because it would result in a clearance of 0.20, which is 0.01 tighter than spec. Better to go with 1.75, which should result in a clearance of 0.25.
One additional complication, it's important to measure the shims that come out of the bike to make sure they're actually the size they claim to be. If they're worn so that they're not the indicated size, of course the math has to be done according to the actual size, not the indicated size. There is a chart in the Yamaha service manual that helps with this.
Measuring shim with digital micrometer
The new shims should go in number side up and should be seated correctly. They are a tight fit and it's easy to seat them at the wrong angle. They should be flat relative to the rest of the valve, and not stick out of the shim seat much at all.
Cam Reinstall
After installing the new shims the cams need to be reinstalled and the valve clearances double checked. The cams and everything they come into contact with need to be lubed with molybdenum disulfide grease during reassembly. So I did that and was eventually able to get the cam sprockets back underneath the cam chain. However the other ends of the cams, the non-sprocket end on the left side of the bike, were sitting high up off the engine and didn't seem to want to sit on the buckets properly. I got the feeling I was applying too much pressure to the cams to get them seated properly and thought I must be doing something wrong. Not knowing what else to do I asked for help from the FZ1 list and waited. They were quick to respond, but I'd wasted a lot of time trying to get the cams in with the sprockets attached, and the day was pretty much done.
It turns out that the Yamaha service manual has a different procedure for cam removal and the folks on the FZ1 list assumed I followed the Yamaha procedure. Yamaha says to remove the cam sprockets while the cams are still installed in the engine, and reinstall the cams without the sprockets attached. So I had to figure out how to remove the sprockets with the cams out of the bike, in order to reinstall the cams. Eventually I was able to accomplish this using the cam chain to hold the sprockets, while I kept the engine from rotating with one hand and loosened the cam sprocket bolts with the other. It was really awkward and there was strong threadlocker on the sprocket bolts. I'm lucky I didn't round any bolts or break anything. In retrospect it probably would've been better to remove the bolts with an air wrench and 10mm impact socket, but I didn't have an impact socket of that size lying around. It would have been better to have taken a break and gone to the hardware store.
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