Friday, 11 July 2014

It's been a while...

About a month actually. Ariel time in the last 4 weeks has been spent on a number of fronts: 
  • welding cable guides inside the rear mudguard 
  • finishing the wiring 
  • messing about with the valve timing 
the latter item has been the most frustrating. I have a good set of guidance notes from Draganfly, written by Bruce Longman which I have followed religiously.

I assembled the head using on cylinder number 1, as I thought I would make it easy on myself and avoid having to turn the cam against four sets of valve springs.

Initially I tried the Waller-style method of aligning timing marks.

Having done this I turned the engine over to see the exhaust valve opening half way down the power stroke. Bruce says that sometimes the factory timing marks don't give the correct timing, so I tried again... and again... and again... eventually getting the timing discs and dial test indicator out to do the job the long way, all the while getting more and more proficient at releasing tension on the cam chain, removing the nuts, drawing off the crankshaft pinion before I could remove the cam shaft pinion... Always the same result.

Eventually I started doing this more scientifically, drawing the valve event charts and calculating overlaps & durations. This is what it is supposed to look like:

Frustrated with Cylinder #1, and confused by the fact that #1 runs backwards, I changed to #3 and drew another diagram:

This revealed that #3 was about 180 degrees out; while #1 inlet valve was correct and #1 exhaust valve was about 180 degrees out too. Confused, I thought about looking at #2, which was doubly frustrating because one of the pushrods would not go in the tunnel.

I set and reset valve timings for about a week, and then one day, looking at the rockers, pushrods and convincing myself that #1 inlet must somehow be on the wrong cam, I started looking at the #2 inlet pushrod problem when I happened to glance down the #1 inlet pushrod tunnel - to see the pushrod going off at a weird angle.

I now know it is possible to get a SQ4 pushrod in it's neighbour's tappet. #1 inlet was in #2 inlet's tappet, so it was operating from #2 inlet's cam! Now that I realise what I am looking at, it's obvious.

Ho hum. we live and learn. At least I found it before I pulled the head off again!

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