The next fly in the ointment was the discovery that the 164 oil pump shaft doesn't rotate at half crank speed. For some reason Alfa changed it for the transverse installation to 70% of crank....
So that meant that I had to get a gearbox made up to drop the revs to what the rev counter needs to see to read correctly.
Fortunately this also solved another smaller problem, not having to turn the cable through a tight curve.
Some progress there then but the next one took some thought...
Guy
So, I needed to get a spare driven gear and extend it up through the top plate. And you might have also noted the nut on the top of the driven gear? A bit of research at AHM turned up a replacement top plate with an integral bearing and a hold down shaft for the Alfa 75 for owners who drop the dizzy and replace it with electronics. So I bought one of those kits and it looked promising until I realised that the shaft was turning the wrong way and would unscrew under load from the cable.
So, after a lot of thought and discussions with an engineer willing to take this on we ended up with set up below. A top hat (silver soldered to the driven gear). The bottom of the extension has to be hollow to take the threaded section on the top of the pump shaft and the top part was machined for an interference fit for a plastic shaft recovered from the spare gearbox with the square section to drive the cable. This plastic shaft was turned down to length so that it was the same as the Alfa 75 dizzy base plate to driven gear.
So that's what was done.
Guy
Finally the AHM cover plate needed to be drilled through for the shaft and a new threaded boss for the cable attached.
Job done.
Guy
And with all the components sorted out this is what the assembly looks like on the bench.
Time to install the assembly then. Well, you can see it went in okay but it took a while to get in.... The retaining nut and washer came off very easily but the driven gear wouldn't pull out with a magnet. Or a pair of pliers. Or welding rod slid under the gear and pulled up.
So, time for a bit of thought and a coffee. Key in the ignition and cranked it over a couple of times and the gear rises up the shaft easily and could be pulled out.
Dropped the new assembly in but the top plate wouldn't settle down fully. Slight panic - was the shaft too long? A dry assembly without the "O" ring showed that it was okay and that's how it has to stay for the time being. Unfortunately the engineering company removed the AHM one when machine the the top cover and misplaced it so I need to get a new one. I attempted to use one from the old top plate but it was too wide and had to be cut down. Even then it was too thick or the groove in the cover plate too shallow as it just wouldn't fit into the engine with the seal in place.
So now I'm waiting for a new one from AHM now... Hope Adie stocks them!
Guy
Okay, so I didn't want to run the motor without the missing "O" ring just in case....
But I changed my mind and fired it up and the rev counter worked!!
RESULT!!!
A nice report Guy. Well done with the dedication!
A few years back I bought an "o" ring selection box from Machine Mart. Don't know if they still do them?
Anyway, if you can get hold of one there is a fantastic selection of diameters and thicknesses in it and I've never been short of a ring since.
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