First time inside a desmo valvetrain, couple questions: 1. Both intake valves have broken half rings. Is it advised to replace just the intake valve rings, or shall I replace all of them? 2. I understand new half rings will take up some room in the closer clearance. My plan is to order the shims I need for the exhaust valves and get those dialed in, but hold off on the intake valves until I pop the new half rings in and re-measure the intake clearances. Is this the way to go, or is there a relatively consistent amount taken up by new rings vs old that I can account for and go ahead and order the intake shims with the compensated measurements? Thanks.
I'd go with your first suggestion unless you've got a selection of shims to hand. Don't forget you can use wet and dry paper (also known as Emery cloth) to sand down the opener shims on a truly flat surface like glass or machined metal. It takes a while, you need to keep rotating the shim regularly to ensure that you sand it down evenly and you'll only realistically take off 2 or 3 hundredths of a millimetre unless you don't have a life . I often stick a biro or something in the end of the shim to save sanding my fingertips too much. It doesn't take too many services for you to build up your own collection of shims that you can swap around this way.
Right, I'll head into town and grab some new half rings, then install and remeasure. Just discovered a missing chunk in the vert. exhaust half ring, so looks like 3 out of 4 now... at this point I think I'll just replace the whole lot of them. Good shout on sanding down the shims... all my closers are loose, and both my intake openers are tight (exh. openers are spot on). Suppose I can shave the openers as needed and just replace the closers, save a bit of coin. Course I won't be sitting there sweating balls trying to polish them down, that's what the lathe is for
Don't forget that often all you need to do is simply swap some or all of them around to get the valves within spec.
Indeed, unless you have a stock of shims it's worth measuring everything first just in case what is too big in one is just right in another...
Right, new half rings bought and installed. Both ends shrunk on the exhaust valves and the closing clearances shrunk on the intake valves but the openers stayed the same. Interesting, because the intake rings were the ones that were broken... and it seems I was seeing things, as both exhaust valves had intact half rings when I went to pull them. In any case, I think I can shave one of the closer shims down (have a 3.20 and another cylinder calls for a 3.18) but the rest need to go up in size. As for the opening shims, I'm a bit unclear... will my opening clearances change when I change the closing shims? Or am I not thinking about that correctly and they're independent of each other?
the size of the openers are independent to the closers as you said latterly. I always use a grindstone to reduce openers particularly exhaust as they often need a lot of material removed, as said, a good fitting biro or aluminium shaft et cetera inserted in the shim makes it a really easy job once you dial your eyes in.
Also don't be surprised if what you carefully measure and calculate as the necessary new shim size, does not seem to work out exactly in practice! Firstly don't rely on the size marked on the shim itself, even if it's meant to be brand new. There are machining tolerances and it maybe that it's not actually brand new and has been pulled from a stock of shims at the dealers. It may therefore be secondhand and worn, or has already been sanded down! Secondly, valve shimming is as much an art as a science. Sometimes even if you've taken all the care in the world the result is still not precisely what you predicted. That's why they are called 'feeler' gauges and 'f'eel' is not exact from one day to the next in my experience . Anyway, good on ya for having a go! It's not as hard as the magazines and some 'experts' would have you believe, as you've obviously found out. You've just saved a bundle of cash and know your bike better. The valves will probably be shimmed more accurately too, as you're not under the same time constraints as a dealer's mechanic either.
Thanks for the tips gents, much appreciated. Specially glad to hear that the clearances are independent of each other, makes things a fair bit easier. As an aerospace machinist/welder , I don't foresee having much trouble with removing a bit of material The ones that need more than .05mm or so taken off will probably go in the lathe first, then I'll finish em all out on a stone or some 500ish grit paper. On the subject of measuring... I've discovered that 1/4" drive 6pt 4mm and 5.5mm Snap-On sockets are a near-perfect fit in the opener and closer shims, respectively. Both measure consistently at 22.38mm in height checked at multiple points and seriously fit incredibly well. Brand specific though as I tried some other sockets out of my shit pile hoping to dedicate a couple to the task and they have too large of a diameter. The proper tools from EMS may be cheaper though Tomorrow I'll double check the numbers and figure out exactly what can be moved and what can be shaved, then Monday at work I can do any modifications, and Tuesday when the bike shops open up again I can grab what shims need replacing. I'm shooting for a .1mm opening clearance and a .025mm or smaller closing. I expect the new half rings to settle in within a few hundred revolutions, so I'm not too worried about a tight closing clearance and it seems tighter is better on that end anyways. Then I'll check and adjust if necessary in 1500km or so.
Sounds good mate, best of luck and enjoy the extra cash the Ducati 'mainstealer' would have charged you
