I am in the process of checking the valve clearances on my NC24 and want to pose a couple of quick questions:

1. How far under the cam lobe should you be able to insert feeler gauges to check clearance? I can get mine under no more than 5mm.

2. Is it normal for clearances to be tighter than specification. I would have thought through time they would loosen up rather than tighten? Surely if I increase clearance to return to get within specification this will be at the expense of cylinder compression.

Cheers

1. Aren't you supposed to measure the clearance between the shim and rocker arm?

2. It's normal for them to go either way, just get them back in spec

There are no shims on the NC24, adjustment is via a locknut and screw setup. My question is how far under the cam lobe/rocker arm should the measurement of clearance be taken as on mine I can get about 5 mm in before there is zero clearance. (on all valves)

Silly me, I understand now. No idea though......

fasttom wrote:I am in the process of checking the valve clearances on my NC24 and want to pose a couple of quick questions:

1. How far under the cam lobe should you be able to insert feeler gauges to check clearance? I can get mine under no more than 5mm.

2. Is it normal for clearances to be tighter than specification. I would have thought through time they would loosen up rather than tighten? Surely if I increase clearance to return to get within specification this will be at the expense of cylinder compression.

Cheers

1:

Are you measring them right? ie with the feeler gauge flat (parellel) to the valve surface / rocker arm?

Providing theres nothing in the way the should slide in freeley, with a little drag if you have the right clearance. It sounds as though there not flat or your catching them on something or your using a blade that is much too thick. (0.18mm if fine for exhast)

2:

Valve always tighten up usually (ie the cleanreace gets smaller) which is why you normally replace shims with smaller shims if you have shimmed bike (to increase clearance) or loose up the locknuts (as in the case on the NC24)

The vavles themselves eat into the head slightly overtime and this takes up the clearance (as well as any marginal stretching of the vavle)


Valve clearances per-se have nothing to do with cylinder compression at all. Compression is measured with the valves closed and the piston compressing the bore.

Leaking valves will affect compression as it wont be able to seal properly, also if your vavles are too tight they can be held open too long by the camshaft. This will be reducing cylinder compression as they are still open when they should be closed thus letting gas escape.

If anything you will restore normal compression if its down.

I am measuring between the cam love and the rocker arm.... am I making a stupid mistake by doing this?

Makes sense I suppose when you thing about it with them tightening as the valve seats wear down.