need some help with VDST

[Mr Earl]

I hope this isn't too much of a threadjack, but are there any web sites that cover the step-by-step procedure for cam degreeing?

[Langanobob]

Quote from Scott

Advance the timing a little and you get less low end torque but more top end power.

Scott, great write-up on the  VDST and I vote to make this thread a sticky.  Just one minor comment about the effect of advancing or retarding cam timing, I think I remember from a long time ago that counter-intuitive as it is, advancing the cam timing helps low end torque at the expense of top end power.  I think it has to do with the valves closing sooner and keeping  more fuel in the cylinders at low speed but the same earlier closing at high speed hinders exhaust scavenging.

Not 100% sure and maybe brad black has something to say on this topic.

[scott_araujo]

Could be Bob, I might be wrong on that one.  As I understand it, advance (to a point) is bad at low speeds because you are firing before TDC and so fighting the piston.  At high speeds this is good because the piston is moving so fast the flame takes some time to travel.  If you fire at TDC you're already half way down by the time the pressure kicks in, so you fire before to sort of race the piston a bit.  Of course if you really want the best of all worlds you need to look at fancy engines with both variable ignition timing based on demand and variable valve timing with pneumatic valves.  Power when you want it, super economy when you don't.  But beyond the scope of this discussion.

I don't think there's a Duc specific sight with full details.  There was one with some stuff.  I read all I could from various sights and found one sight where they were done end to end on a v8.  Once you have the concept it all falls into place.  I thought about writing it all up but it's a lot to tear the bike open, go through it all, take pics, write it up, especially if you've already done it and don't need to actually do it for the bike.

Tools: maybe a piston stop, see below.  Other than that, no other special tools than what you already have.  You're not going to be removing the castle nuts or pulleys.  There are three little allen bolt you loosen.  This lets the outer toothed wheel spin in relation to the inner one that is bolted to the camshaft.  Measure, figure out how far you need to move, loosen, move the cam shaft a little, re-measure, realize you went both too far and the wrong way, curse, skin knuckles...  Eventually it works out

I degreed mine on the intake valves.  The intakes are more critical than the exhaust, the exhaust gases move themselves out with force.   With a two valve they're both on the same cam shaft so you only set one.  4v bike not only have two camshafts but a whole world of overlap to be explored since you adjust them independently. 

Also, I set the degree wheel to 0 at TDC  for each cylinder.  You can just work off one being 90 degrees out but the math got confusing for me.  I was already confused trying to remember which way to turn everything.  Also, I didn't read the TDC marks from the bike, I set them.  I got a piston stop.  Turn it it a little ways, rotate one way until it stops, measure, rotate the other way, should be the same reading in the other direction.  Again, if you're going to this much trouble you may as well get TDC right.  It's easy for the marks to be a degree or two of or for one cylinder to be a bit off from the other.

Scott

[Speeddog]

Don't confuse ignition timing with cam timing.

[brad black]

http://www.bikeboy.org/camtime2v.html

see the 800m and s2r800 reports too

[scott_araujo]

Don't confuse ignition timing with cam timing.

Sorry if I did that, didn't mean too.  As I said, that discussion is beyond this scope but with pneumatic valves you can do things like effectively modify your cam profile as you want.  Just really cool possibilities.

Scott

[booger]

OK, ran the part #s for the Ducati tools required for this job per the factory shop manual and of course they are obscenely expensive. From my understanding you need 1) 2 dial indicators, one for intake and exhaust fitted simultaneously (Harbor Freight $11.99 and $14.99 for the deluxe model) 2) a piston stop tool ($35.99 from CA Cycleworks) 3) engine turning tool ($65 from CA Cycleworks) 4) a degree wheel (I made a really nice one in AutoCAD, printed it out on regular paper, and spray-mounted it to a sheet of styrene plastic) 5) feeler guages (get these somewhere for ~$10) 6) some sort of holder for the dial indicator (I'll probably make one out of something that screws into the threaded holes for the valve covers)

The shop manual instructs to tension the horizontal and vertical belts to 145 and 160 hz respectively for this procedure, which obviously differs from the running tension of 110 hz on both belts(I think the 110hz spec is a revised spec from Ducati, implemented after this manual was published, so I assume tensioning to 110hz is correct for this procedure). After turning CCW and CW a few times, measuring angle @ 1mm lift on both intake and exhaust, you arrive at final numbers. Allowed deviation is +-3deg from spec cited in the manual

OK, so what do I do now? Loosen the three allen bolts on the cam wheel and do what? This information is curiously absent from the manual.

[scott_araujo]

You only need one dial gauge (see below).  Don't bother with the articulated magnetic bracket from HF, didn't work for this job.  You can make one that will work from a stiff piece of wire.  It just has to hold the rod of the gauge in the same line as the valve.  I found a piston stop for $15-20 somewhere else.  It's a weird size but people have them, look around. Their engine turner and degree wheeel are NICE!  But you can make do with any engine turner that you can find a way to stick your home made wheel to.  No, you cannot turn the back wheel.    This is delicate work and you need precise control.

So, unlike a 4v your intake and exhaust cams are on the same camshaft.  The intake is really critical, you want that valve opening and closing exactly when it should.  Exhaust, who cares?  That high pressure gas is going to blow right out of there even if it's a few degrees off.  So, if your cam is weird and it looks like you can't get the intake and exhaust to exactly where they both should be what do you do?  Since you can't set them individually do you compromise and set in the middle?  No, you set intake.  That being the case, why even measure exhaust except for curiosity?  Can't remember if I read this somewhere or it's just my own opinion I formed.

On a 4v they can and need to be set individually and you can make the cam profiles overlap more or less.  This can create a momentum where both valves are open for just a bit and the exiting exhaust gas leaving creates a vacuum that can pull in the next fresh charge.  Heavy duty tuner stuff, way above my head.  Most profiles are set up this way even on a single cam shaft, but you can move it around if the exhaust and intake are separate.  On our 2v bikes they are together so you just get to pick one setting and both lobes advance or retard together.

I just set the belts really tight, as tight as I could, and called it good.  I also set my regular running belt tension with a 5m allen and move on.  It's no rocket science.  The higher blet tension for setting cam timing is based on removing all the slack from the system.

Ok, so go to Ducati web site and look at the exploded diagrams for the cam.  You'll see the separate hub and outer toothed wheel.  To change the setting: with the belts on undo the three little allen bolts so they're loose, grab the castle nut with some pliers, and genltly rotate the caslte nut.  It should move pretty freely.  You're not tightening or loosening the nut here, it's just attached to the cam that you want to move and is easy to grab.  You should see it move relative to the outer toothed wheel.  Then retighten the allen bolts, or at least one of them.

Once you have the technique down it's a bit of trial and error.  You go to TDC, rotate the engine watching the the dial until it reads .050" of lift, record the degree reading, rotate through the cycle until you hit .050" on the down side, record the reading again.  The spot dead between the two readings is your peak lift.  Figure out how far you are off, guess at which direction to turn the camshaft, adjust to your best guess, rotate and measure again, adjust again, etc.  It's trial and error.  Never rotate the engine backwards.  You don't want the slop in tolerances in the engine coming into play.  Going in one direction keeps all the pieces against each other.  If you miss a read just go around again.  Also, measure everything 2-3 times.  You want to be sure you're getting it right.  When you're done I'd say loc-tite and torque those three little bastards down.  Did I mention mine came loose right after I bought the bike?  Big thanks to Howie for diagnosing and talke me through it all.  Not a fun time for a new Duc owner.

The .050" before you read the degree reading is 'ramp up'.  It's really, really hard to tell exactly where the cam lift starts but easy to tell when you're .050" above dead bottom.  Use .050" above on both ends and it all evens out.  

Go slowlly with all the engine turning.  If you go way too far on cam adjusting you might get to a point where the pitson hits the valve and things can bend.  That's bad and expensive.  I know this can happen with the aftermarket pulleys, maybe not with the OEM.  Mine was totally loose and flopping around.  I drove several miles home on one cyclinder and didn't bend anything.  Oh, and make a nice little paint mark on the cam wheel to the castle nut before you start.  If you totally screw up it's nice to be able to get back where you started and ride to the shop instead of towing it.

Scott

[Mr Earl]

Been reading various web sites about degreeing cams and starting to get an idea of the process.  One detail that's nagging me is, how is the dial indicator set up to indicate movement of the valve/rocker on these 2V Ducati motors?  The opening rocker blocks the valve/shim area, and the top of the rocker doesn't seem to be a good surface to place the indicator tip.  Or is there some giant flaw in my thinking on this?

[Speeddog]

Here's one I made for 4-valvers.

Catches the edge of the closer shim.

[booger]

The spot dead between the two readings is your peak lift.

could you elaborate?

[scott_araujo]

Been reading various web sites about degreeing cams and starting to get an idea of the process.  One detail that's nagging me is, how is the dial indicator set up to indicate movement of the valve/rocker on these 2V Ducati motors?  The opening rocker blocks the valve/shim area, and the top of the rocker doesn't seem to be a good surface to place the indicator tip.  Or is there some giant flaw in my thinking on this?

Nope, that's the way it is.

The end of the rod on my dial indicator unscrews.  I unscrewed it and put a small washer on there.  I then lined up the rod parallel but just to the side of the valve stem.  There's enough real estate on the opener shim to have the washer ride on it's edge and not get in the way of the rocker.

Scott

[scott_araujo]

could you elaborate?

Sure.  Split the degree wheel up: 0 is TDC and on either side you have 1-179 Before TDC or After TDC depending on which side, and 180 or BDC.  Let's say you read .050" lift at 29 BTDC on the upswing and then you read .050" at 38 ATDC on the down swing.  (These are random numbers, I have no idea what the real values are supposed to be off hand.)

Where's the middle?  Between the two points on the wheel in the section you rotate through.  -29 + 38 = +9 or 9 ATDC for this made up example.  That is, the peak lift occurs here. The tricky part comes in when you try to do the math and span different parts of the wheel with BTDC, ATDC, etc.  Then if you try to do the second cylinder without setting TDC to zero you have to add or subtract 90 from all your angles.  Then which way do you rotate the cam relative to what you need?  And twice as many degrees as you're off because the cam goes around only once for each two revolutions of the crank shaft.  Another benefit of making your own degree wheel is you can write all over it.

The basics of the process and the specifics of the math are laid out on other gear head sites.  You don't need to be on a Duc motor to get the idea.  Look around, they're out there.  Also, just set it up and don't loosen anything.  Find TDC, set your degree wheel, measure your lift as you rotate.  Where does it start?  End?  Just looking at things won't do any harm.  Once you see it all in front of you it will make so much more sense.  Or maybe it is time I just pop the covers and do a pictorial.  We'll see, lots of family stuff going on lately and not much time.

Scott

[battlecry]

"Another benefit of making your own degree wheel is you can write all over it."

Well, Scott, I got my wheel from Chris and I still wrote all over it. 

[brad black]

i've posted a couple of photos of my tool on my blog here - http://bradthebikeboy.blogspot.com/2010/04/some-photos-for-monster-list-of-dial.html

it's a piece of coat hanger wire bent up.  coat hanger wire is great for this stuff.  dial indicator mounting bracket is a piece of bent steel and an from a dial gauge holder of some sort.  make a solid stand.  if it moves, it'll piss you off.

i only ever turn the engine one way too.  never backwards when doing this.  i set the belts to the normal running tension, never bother taking out the clearance and check lift at the spec of 1mm lift (0.040").  but that's just convention.  using the calc centreline method it doesn't really matter how much lift you use as long as it's around that.  some of the cams are assymetric so at some point you might get a shift due to that if you go with 3 or more mm lift as your check point.