Timing 900 2 Valve Carb Engine From Scratch

One of the jobs I want to get done over Easter is finish the build up of the 900/966 engine in the SS mongrel I’m putting together.

The bottom end is completely rebuilt with all new bearings and accurately shimmed to tolerance, the barrels are on with new piston rings in glaze busted bores, and the heads are now rebuilt with the valve shims finished.
I’ve matched the Con rods, pistons and Gudgeon pins weight wise by bringing the heaviest down to the same weight as the lightest, and ensured that the con rods ends are also weight matched.

Once the Heads are torqued down I’ll use a stop through the plug hole and my degree disc to accurately find TDC and start from there.
It will be interesting to see how far out the standard mark is out through the little window in the left hand case.

Partly because an element of this exercise was to blueprint the engine as best I can at home for the fun of it, I’m going to be using a pair of adjustable camshaft pulleys to dial in the timing as close to ideal as possible.

I’m not new to doing this as I’ve used adjustable sprockets on old Z1000’s and Hillman Imp engines in the past, but got to the point where I just knew roughly where to set the cams before placing the chain on the sprockets.

As I’m new to building up a Ducati Twin from scratch I need to establish a starting point and look up the optimum timing.
Can anyone help with a schematic that shows more than just the various standard marks on pulleys, perhaps explains what’s happening with the valves at the point the marks line up.
What’s the optimum timing suggested to be?

Once I’ve got TDC set accurately I’ll also be moving the ignition pickups to match.
Again, is there any grains of wisdom on this using normal forecourt fuel?

Thanks

Nasher.

 

Derek
That look's like some decent bedtime reading - thanks

Nasher

 

The Heads are now torqued down, everything is checked, and I even gave the engine a coat of VHT paint over the weekend before I put the belts on.

Have read and believe I understand Brad Black's extensive article, so all I need now is a couple of hours of peace and quiet over the coming weekend to dial it all in.

I'm going to go with standard factory setting to begin with, then swing the timing towards what Brad has found after the engine is running.

Nasher.

 

After being diverted onto other bits an pieces for a while I managed to find an hour to myself this afternoon so thought I'd have another look at this valve timing.

First thing I wanted to do was check how accurate the flywheel mark and cambelt drive pulley marks are in comparison to actual TDC on the front pot.

Up until the last couple of years I've not touched a Ducati engine, but have worked on lots of old Kawasakis, Yamahas, and mainly Suzuki Outboard engines. I've not found one to date with accurate TDC and timing marks and was expecting the same with the SS Engine. Most I've found are 2 or 3 degrees out.

luckily I already had a 'Stop' knocked up from working on a previous engine, I think in this case one of the Suzuki Outboard engines I've built over the last few years.



Using the usual degree disc method of winding the engine back and forward against the stop the improvised pointer shows the 'degree' in both directions and of course TDC is at the halfway point between them. In this case 29 degrees.
Ignore the fact that it's 29 degrees, it means nothing, it's just halfway between the two.



At this point you'd usually turn the degree disc to 'TOP' or '0' but for what I was doing I didn't need to.

I have to say I'm impressed.

At my calculated TDC point the flywheel mark looked like this:


And the cambelt drive pulley looked like this:


These are easily the most accurate marks I've ever seen on an engine, well done Ducati.
Over the weekend I'll be able to get the belts on and move on to another aspect of the build.
I've already set up the adjustable driven Cambelt pulleys I'm using on the cams to accurately reflect a set of standard pulleys as a start point.

Nasher