Valve adjustment question - Ducati.ms

Ducologist · Dec 13th, 2011, 1:19 am

When checking the clearance, should you have to put some upward pull on the opening rocker arm in order to get the feeler gauge in? When I was watching the CA Cycleworks video, the head was off and no upward pull was necessary. Without pulling up I can't get a feeler in at all. With some upward pressure I get .004.

When I pulled the valve cover and looked at the desmo valve for the first time, I nearly wept. 'Tis a thing of beauty.

va duc · Dec 13th, 2011, 2:07 am

No you shouldn't have to lift them. Are your belts off? Its possible to have the cams close to the position they need to be in but just a tick off. Try repositioning the cam just a bit.

Ken · Dec 13th, 2011, 8:11 am

I would double check to make sure your at TDC. However, when the valves are closed, a .10 feeler gauge should slide in with no drag.

Ducologist · Dec 13th, 2011, 1:46 pm

Quote:

Originally Posted by va duc

Are your belts off?

Belts are on. At TDC based on the sight glass, and verified with a drinking straw.

ducsbill · Dec 14th, 2011, 12:28 pm

Quote:

Originally Posted by Ducologist

When checking the clearance, should you have to put some upward pull on the opening rocker arm in order to get the feeler gauge in? When I was watching the CA Cycleworks video, the head was off and no upward pull was necessary. Without pulling up I can't get a feeler in at all. With some upward pressure I get .004.

When I pulled the valve cover and looked at the desmo valve for the first time, I nearly wept. 'Tis a thing of beauty.

I have noticed that sometimes it feels like the thin film of oil is causing them to "stick together". Running the feeler gauge in and out a few times and wiping it down seems to cure that problem.
Bill W.

va duc · Dec 14th, 2011, 6:17 pm

Quote:

Originally Posted by Ducologist

Belts are on. At TDC based on the sight glass, and verified with a drinking straw.

Ok, you still have to rotate the cams a bit to git the rocker arm to slide over to remove the shims, I still say your just a bit off.

Ducologist · Dec 15th, 2011, 2:09 am

Quote:

Originally Posted by va duc

Ok, you still have to rotate the cams a bit to git the rocker arm to slide over to remove the shims, I still say your just a bit off.

Yup. I get slightly different measurements when I move the cam position. Still not certain I'm measuring in the right place though. Does it matter where you are on the cam as long as the valve is fully closed?

va duc · Dec 15th, 2011, 5:48 am

I always jostle the cam around to get the largest clearances and go with that as my mesurement, and I always remove the belts, it makes the job so much simpler. That allows you to move the cams around a bit and still have the piston close to TDC in case a valve drops.

Ducologist · Dec 16th, 2011, 10:24 am

Quote:

Originally Posted by va duc

I always jostle the cam around to get the largest clearances and go with that as my mesurement

Ok. So if I'm understanding it correctly, in a perfect world the cam lobes would be perfectly consistent across their rotation. But there is going to be some variation in clearance due to wear and acceptable to tolerancess in the manufacturing process. When we measure the clearances, we are looking to measure the greatest clearances across the closing sections of the cam lobe, rather than the smallest, or some other specific point during the closing rotation (TDC of compression stroke, for example). Can a motorhead tell me if this is correct?

wdietz186 · Dec 16th, 2011, 3:20 pm

More than likely the difficulty you are having has more to due with the shim than the cam position. The shims top and inside surfaces are not always square so there will be a slight difference in clearance depending on its position.Also due to the ID of the shim being larger than the stem it is sitting on the shim will cock slightly as you try to insert the feeler blade. You can also attribute some of the problem to the clearance of the rocker on its spindle and the oil film you have to squish out of the way as you insert the gauge. All of these variables will conspire to drive the truly anal to distraction.