Since the last time I wrote about the W/NG, we have been locked down again and are only now seeing the light at the end of the tunnel. We've had snow, freezing winds, and Christmas, if only for a day or two. It's had very few outings since the COVID crisis is a very bad time to be needing the services of A&E in a hurry should the worst happen so I have been painting (a house), making an airbox for the QR50 and turning parts for the Model A.
However, painting a city centre house means you need to get there and park, which is much easier on a bike so I have used it a couple of times. You might recall I put an old Lodge HN in it, to see how a traditional plug would behave - well, it failed after 200 yards and a new W8AC went in. This was fine for the rest of the commute, testing the new main jet, but the high speed thrash along the main road had us arrive back coughing, spluttering and sooting up.
Back to square one. I decided to replace the float needle, which was an old one:
Can't see what's wrong with it? No, that's because it's hardly worn. The fuel level was quite high:
Messing about with the float bowl got the level down a lot:
It ticks over nicely:
I wasn't convinced that it would make the difference, and looked back over some old pictures only to realise that the throttle needle was not, in fact new... I bought another and made a comparison:
Here, I've marked the old needle (bottom) and the new needle (top) every 10 mm. The chart below shows the diameter at each position in thousandths of an inch, with the difference in the 'wear' column on the right.
When you consider that the needle jets are sold in increments of one thousandth of an inch, wear of up to six thou' in the needle is very significant.
It has to be said, this is a schoolboy error if ever there was one - I should have bought a new needle at the outset, I would have saved a fortune in spark plugs.
A 50 mph thrash down to Weybourne produced this colour in an old B5HS.
And the fuel level? I'd set the float so low that the valve could hardly open. I could ride a couple of hundred yards and then it would splutter to a halt, and I would have to wait while the float bowl filled up again!
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 only 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!
