Calculating Multiple Tight Valves Without Multiple Cam Removal?

I don't see a shortcut here. The shims are not horrendously expensive and if all 12 are out a shim kit box maybe cost effective. I think I would buy new shims based on all clearance values being “zero" and buying the relevant shim based on what shim is already in that position in the normal way. When you get the cam back on you might end up with a handful out of spec that need an alternative shim size. Those could be changed with the shim removal tool without taking the cam back off. If you think you have taken a considerable amount off with the valve lapping maybe assume all gaps are -0.005 and start there?

 

If the shims are on top of the bucket you’re laughing and can use a shim removal tool, if they’re under the bucket you have no choice but to take the cams out to swap shims.
So you know the size of the shim you removed with zero clearance, right? Assume the valve wasn’t being held open and as @XCaTel suggested take it you’ll lose 0.005 mm by lapping the valve in then subtract the clearance required plus the 0.005 from that shim and select the shim nearest to that measurement as a starting point. That should be close enough and reduce the number of times the cams have to come out.

Edit. So I’ve just looked on world of triumph parts and the diagram shows the shim on top, good news. The shims vary in price from £4 to £8 but bear in mind you should be able to move them around in order to get the right clearance, you won’t need to buy all new. Best of luck.

 

Sorry for the late reply, you are probably sorted by now. That is a good way to proceed and you could get real lucky with that approach, best of luck.