paulincayman said:
Mate that's huge info ..was sat here wondering where in the world(literally) to send them or to fit the spare a11s...so a diy fix would be perfect .
Going to pluck up the courage to lift the barrels off tomorrow.
Can certainly be done as a DIY project. The way I did mine was a kind of iterative process of flipping and changing sprockets, moving the chain on the teeth and re-checking the timing. When I got within a few degrees, the fine tuning was done by filing the bolt holes. It was a tedious job assembling the top end, measuring and disassembling each time. I reckon I had the cams in and out about 20 times! It also required the use of a degree wheel and a dial gauge to measure valve lift.
If I was to do it again, I'd adopt a different approach - drilling and taping new bolt holes. That's an easier process because you don't have to assemble the thing for check measurements all the time. It's arguably a better engineering solution to the way I did mine anyway because you don't have slotted holes that could slip out of position.
Position the new holes in line with the sprocket teeth as shown on the 4C sprocket drawings (doesn't matter which teeth you choose). Reassemble the cams and install them in the correct position. Job done. No need to dial in with a degree wheel (unless you're a bit obsessive).
To get the right position, mark the pitch circle diameter using the existing hole centres as a guide, then scribe a line across the sprocket from tooth to tooth tip through the centre of the sprocket (cam sprockets always have an even number of teeth). Where the line intersects the circle gives you the new hole positions. Centre punch, drill and tap to M6. If you're not confident to do it accurately enough yourself, take them to an engineering shop. They can set the sprockets up in a milling machine and get the holes spot on.
Obviously the original timing marks will no longer be valid, so you'll want to make some new ones. They're necessary to get the cam chain back in the right spot when you reassemble, and after every time you do the shims. I didn't put new timing marks on my sprockets, so I have to do it with a marker pen each time before disassembly whenever I do the shims. The reason I didn't out permanent timing marks was just laziness. Once I got the valve timing right, I thought, "Fuck it. I'm not taking it apart again just to engrave new marks".
The sprocket drawings tell you where the marks need to be. All you need is a protractor to transfer the angles onto the sprockets. Might be a good idea to grind or polish the old timing marks off and block off the old bolt holes to avoid confusion.
You could make new marks with a small grinder or Dremel using the edge of a cutting disk. But maybe a neater solution would be to use an engraving tool. You could also re-do the A and S with the engraver. I reckon the sprockets might be too hard for letter punches. You'd just bugger-up the punch.
Most of us don't have an engraving tool lying around, but you could do the marks and lettering with a fine tip permanent marker and take them to an engraver and get him to over-write them. Most key cutting shops do engraving.
Might be worth a closer look on yours as well.
