Newby valve adjustment - Ducati.ms

longdrive · Jan 18th, 2012, 7:33 pm

Just doing some research and found this article from ducati meccanica,

Setting desmo valve clearance

Godfrey sets some mins & max numbers I thought were interesting. I just checked my clearances on the vertical and about to rotate & double check & also measure the horizontal. These are my initial readings using the method of measuring the opener then depressing the closer and subtracting, openers first, closer second. Intakes .003/.003 & .005/.002, Exhaust .007/.006 & .007/.003
Let me know what you guys think, first time

13k on the clock

ducatimike · Jan 18th, 2012, 7:45 pm

On Desmoquattro's I set all closers .002 to .004 in., all openers - .004 in.

Mike

stryder · Jan 18th, 2012, 9:50 pm

Quote:

Originally Posted by ducatimike

On Desmoquattro's I set all closers .002 to .004 in., all openers - .004 in.

Mike

Hey Mike,

can you comment on the statement in that link about checking the clearance on the closers all the way around the cam lobe? afaik, if you set them at TDC, ie valves closed, the cam lobe is at the high spot, and the clearance can't get tighter from there.

ducatimike · Jan 19th, 2012, 6:24 am

Theoretically the cam profile should provide the same clearance at TDC and a number of degrees before and after TDC. But the cam grind has a tolerance and the clearance measured at TDC may not be the minimum. I measure the clearance with the belts on. At this stage you can bump the timing slightly before TDC and after TDC and see if the closer clearance has changed.

Before I change out shims, I remove the belts, the opening rocker arm and the cam. Then change out the closer shim and make sure the half rings are seated properly. If the half rings are tight, I give the closing rocker a good whack with a wooden dowel to seat the closer shim (I always seat the shim when installing MBP retainers). I then spin the cam by hand and make sure there is no interference with the closing rocker.

I have seen the clearances tighten up slightly, but not much on the bikes I have worked on.

Mike

stryder · Jan 19th, 2012, 7:45 am

Thanks for those comments.

nateobie · Mar 4th, 2012, 4:19 pm

Regarding the MBP retainers. I put these on with pre-installation (old collets) closer clearances of 0.003". Now with them on the cam binds. I figured from reading forum posts that people say these new collets add about 0.003." I sanded down one with 400grit by 0.001 and it worked just fine. Then I go the the other side (intake was first then the exhaust). Same pre-installation clearance of 0.003. I put it on and its bound too. So I decide to sand that one down too. Sanded it down 0.001" and still bound. Then to -0.002" and still binds. I'm at -0.003 the original and its still bound.

Is there a minimum closer shim height on these? If they are too small will they bind? I'm thinking I've sanded it down too much and now its binding but that doest make any sense in my mind. If the shim is smaller then it should give more clearance to the lobe side right?

I got the thing bound and had to turn the cam using a oil filter strap wrench around it to get it to turn back to a loose position. I think that was a mistake because now it feels like the cam has some flat spots in it. I hope I didnt damage the lobe surface or bearing surface.

Quote:

Originally Posted by ducatimike

Theoretically the cam profile should provide the same clearance at TDC and a number of degrees before and after TDC. But the cam grind has a tolerance and the clearance measured at TDC may not be the minimum. I measure the clearance with the belts on. At this stage you can bump the timing slightly before TDC and after TDC and see if the closer clearance has changed.

Before I change out shims, I remove the belts, the opening rocker arm and the cam. Then change out the closer shim and make sure the half rings are seated properly. If the half rings are tight, I give the closing rocker a good whack with a wooden dowel to seat the closer shim (I always seat the shim when installing MBP retainers). I then spin the cam by hand and make sure there is no interference with the closing rocker.

I have seen the clearances tighten up slightly, but not much on the bikes I have worked on.

Mike

nateobie · Mar 4th, 2012, 10:36 pm

Well I'm an idiot. I obviously should have checked the openers more carefully because that is what bound. I guess after lapping they had closed to no gap. I took that opener arms off and luckily there was no damage on the lobes or the arms.

I downloaded that desmodue valve clearance spreadsheet from EMS. Thats a good piece of work. Thanks EMS.