1980 900 Exhaust Valve Shim limits?

[HailwoodJim]

Hi guys,
I'm new to the site and hope to learn a lot.
First question: I measured my valve clearances today and the intakes are in spec but the exhaust valves are tight. 0.07mm and 0.10mm. Haynes says the spec is 0.15 but my owner's manual says it's 0.12mm.
Anyhow, I calculate that I need shims of 2.03 and 1.96mm. The local dealer says 2.10 is as thin as they come and I evidently need new valve seats - basically time for a cylinder head overhaul.
What do you guys think? The bike has 25k miles. I've only had it for a few of those miles, so I can't comment on the service history.

[Lumpy]

If it`s your opening shim your saying is tight I have rubbed them down on emery paper on a sheet of glass although taking off .2 mm you may go through the hard casing. If they are indeed surface hardened. I must admit I would think thats a fair bit to rub down.
It`s the closers that are touchy. I cant quite get my head around how your valve seats could compact without giving you big clearances on the closers. Does it idle nicely? Is it getting a little hard to start? These are usualy signs of the closers getting a little loose. As a rule of thumb I don`t mess with closers until they are .003" loose, and then I aim for .001" clearance, I don`t beleive in 0 clearance, I rekon there`s clearance or interferance but nothing between.
I have made a tricky little tool that incrporates a dial indicator that is much better than trying to squeeze feelers in there. Screws onto the tappet cover screw holes and incorporates a screw to wind down by hand and that overcomes the hair spring. You can also check closer clearance around the full profile of the cam. I`ll post a picture of it on here, it`s quite easy to make when I work out how to make this computator accept pictures. Might even post some pic`s of the steeds at the same time.

[wdietz186]

Jim,If the openers are too tight and you are at the low end of the shim range you will need to remove the valves and trim some material off the top of the valve stem.If you have access to a good automotive machine shop with a valve facing machine it is an easy and quick operation to grind .010" or so off the tip of the stem.The only thing to watch for is if there is enough clearance between the bottom of the opener and the top of the closer. You probably wanted to do a valve job anyway,Right?

[HailwoodJim]

Thanks for the replies.
I'm going to have a look at the half rings for the exhaust closers. Steve says they are likely getting squashed. That would necessitate ever thicker closer shims to stay in contact with the cams, although it would have nothing to do with the opener shim situation, right? (As the valve recesses into the seat, the closer shims would have to get thicker and the opener shims would have to get thinner, right?)
Have you guys ever removed the heads with the engine still in the frame? The Haynes manual seems to say this may be possible.

[abmartin]

Have you guys ever removed the heads with the engine still in the frame? The Haynes manual seems to say this may be possible.

Its not possible.

Bruce

[wdietz186]

The horiz. head is easy to remove,Carb,pipe tach cable and four nuts.The vert. cyl. will require dropping the engine out or swinging it down enough to remove the head.To do that removal of the primary and timing side covers is required to clear the lower front frame tubes.You can pivot it down on the lower rear engine mounting bolt.Undo the chain,remove exhaust,carbs, the alt. and ign. pickup leads, [or leave connected and tie the side covers up and out of the way] and starter cables.With a jack under the front of the crankcase pull the front and upper rear mount bolts and lower the engine so the vert. cyl. is at about 45deg.That should give you enough clearance to clear the cyl. studs.If you are going to get that far into it,spring for a set of the MBP valve collets so the closers stay in spec. longer.Steve has them listed along with gaskets and all sorts of neat and shiny things to add to your Ducati enjoyment.

[abmartin]

wdietz is correct. I've never bothered to take the engine covers off when removing the motor but I can see that it should work. I'll try it that way next time.

Bruce

[wdietz186]

you can swing the engine down without pulling the covers and if you are really careful ,strong and lucky you may be able to put it back up without scratching the covers but in my opinion the effort isn't worth it.Plus it makes it easier to check if the timing marks are lined up.

[abmartin]

With my 860GT it was possible to pivot the motor down using the rear motor mount without touching the front downtubes. I have to admit to trying this on my SS and have a small scratch on the clutch cover to show for it. I did manage to get the motor down but it wasn't possible to put it back in place. Next time I'm going with the factory recommendation which is to lift the bike off the motor.

Bruce

[HailwoodJim]

Guys, thanks for the tips.
I took the front cyl head off today. The CC was pretty carboned up. The little half rings that hold the closer shims looked like new. No deformation visible. I will pivot the engine down (cases off) next to get the rear cyl head.
Newbie question: what's the trick to putting the closer rocker with it's hairspring and shims back in place? I tried to tie the end of the spring up into it's deflected position with a piece of soft wire (around the fork end of the rocker), but I wasn't having much luck. Surely there is a home-garage type solution for this little challenge. The spring is stronger than I expected. getting the far side shims in place while pushing the shaft through also looks pretty tricky.
Note: the rocker arm is slightly loose on it's shaft. I can feel a couple thousandths of play there. Is this acceptable? Since both are hardened and well oiled and the rocker only pivots a few degrees, I guess this is OK. ??

[wdietz186]

Jim, Don't forget to drain the oil before you lower the engine.It makes as big mess if you don't.There is a special tool for holding the closer spring for reassembly.I think Steve has them listed .For most operations short of guide replacement removal of the closer rocker is not needed.While you are in the timing side take a look at the ign. pickup wiring and see if the insulation is coming apart.