Valve Adjustment question

[Cloner]

Not to throw a wrench in the works, but every Ducati I've ever worked on with a desmodromic valvetrain had its helper springs on the closers, not the openers.  How does moving the opener over (on bikes where you can do this) relieve the pressure of the helper spring on the closing rocker?

Just curious.

Cloner
ABQ, NM

[EEL]

Not to throw a wrench in the works, but every Ducati I've ever worked on with a desmodromic valvetrain had its helper springs on the closers, not the openers.  How does moving the opener over (on bikes where you can do this) relieve the pressure of the helper spring on the closing rocker?

Just curious.

Cloner
ABQ, NM

I dont know if I can explain it right but I'll try. I will state the obvious first:

If you spin the cam a full 180 degrees with the opening rocker arm in place, you push the valve open. The valve drops down.

In order for the valve to drop the closing rocker arm has to move down in unison. At this point the spring is in tension because it wants to go back to its normal state (closed). There is resistance there.

With the opening rocker arm out of the way, you valve never needs to drop down. So the only drag is from the closer shim being too tight. You can literally spin the cam with one finger with the opening rocker arm shoved to the side. If it drags you will feel it.

[K3V1N]

Thanks again for all your feedback and helpful advice.

My adjustment is finally complete. My openers are all at .004s and .005s won't slide under. All my closers are very close to 0 with no drag on the cam.

So I learned somethings I wanted to share.

When you are measuring shims make sure your caliper and micrometer are clean and all pieces are clean. Oil and other things can throw off your numbers when you are talking that precise measuring.

Take the time to write everything down because there is planning needed to make sure you get the right shims. The first time. Huge thanks to Mike at EMSduc!!!!!!!!! http://www.emsduc.com/

Sanding I found that marking the shim with a sharpie and sanding in a circle rotating it every circle 90 degrees based on the mark worked better for me then doing 8s

Also I found that with 400 / 800 paper I had to change it a lot or I spent a lot of time sanding with no results.

Since all the openers were out of the bike I found that rubber bands worked the best for me to keep the valves up but you have to be careful.

As for the half rings, it took me a while to figure the position of those but after getting a lighted magnify glass from sears and really looking you start spot the wear marks and know the ones on the inside go up.

Just plan on having the closers on and off a lot. I did my math to get to 0 clearance and every time the cam would bind and it would take 2 or 3 tries to get it just right.

Another thing I found was that even though I was spinning the shim in the caliper to make sure it was square make sure to spin the closers once on the bike. 3 of my closers I could get a .005 under very tight when pushing on the helper spring (which probably makes then .0005?) but one of them was just loose enough not to drag. I found that when rotated just right the cam would drag leading me to believe it was out of square a tiny tiny bit. I then tried to find a high spot but couldn't see anything by twisting it in the caliper so I sanded till it would not drag at all in any position.

I hope some of these things may help the next guy or girl doing an adjustment on a 2v.

I can't wait to get get my belts back on tonight and change my oil this weekend because I'm going to finally get my PCIII tuned correctly.

Thanks again

[Cloner]

I see what you're saying, EEL.  Like Ducpainter, I "measure" with the opening rocker dislodged, but I couldn't understand what folks meant when they said it removed the spring pressure.  I guess you're saying it removes all pressure, and thereby friction, from the opener, n'est pas?

Sounds like you got her sorted well, K3V1N.  Good on ya, Mate!