Saturday 15 August 2020

The Final Build and First Start

Stripping the bike back to its component parts is a very quick process – one day maximum. I always put small parts into plastic bags and label them; it is obvious what they are when you take them off the bike but when you have a pile of nuts and bolts 3 weeks later and you’re ready for the final build it somehow doesn’t seem quite so obvious.

Regarding painting and plating, I have adopted the following process:

-     I nickel plate all small items in my workshop – see previous post on the K7plating

-     Items that are too large to fit into my plating bucket, such as the exhaust pipe and handlebars, are plated by a local plating company

-     I send all items that would be have originally been painted, except the petrol and oil tanks, out to a local powder coating company and I always give them an inventory of every part and check that they all return safely

-     I spray the petrol and oil tanks in 2K paint. The lining is also 2K but is hand painted (after masking ….yes, I cheat) and finally a waterslide transfer to which a couple of coats are Humbrol varnish are then applied

There are 3 good reasons for NOT powder coating tanks: the finish from powder coating will never ever be as good as a proper 2K paint finish; you can guarantee that some of the grit from blasting the oil tank prior to powder coating will find its way inside in spite of your best efforts to seal it and you will never succeed in washing it all out properly – disaster for the engine (!) and, finally, the powder coating is baked in an oven at around 185 0C. Many vintage tanks are held together with soft solder which melts at around the same temperature and although only the fittings on the newly-made petrol tank is the only part that has soft soldering, all of these joints would be ruined. My powder coater has told me of the look of surprise and disappointment on the faces of customers when they are presented with a pile of bits and a large blob of lead in spite of being advised not to have their tank powder coated.

The first step is to get a rolling chassis assembled and then to build the engine, sealing the crankcases, and putting in the gearbox.



Because the oil feed to the Velocette cambox is completely different from the original Velocette engine, I decided that I would need some means of controlling the flow rate. To be able to do this, I plumbed a small tap, intended for use on model steam engines, into the  pipework at the cambox end of the pipe to provide a means of adjustment. Before assembling the complete oil pipe system onto the engine I decided to build a (very) simple flow rig to have some idea of tap-opening position vs flow rate. The "Flow Rig" consisted of 3 containers to collect water with the pump-end of the pipework connected to a hosepipe. In the picture below, the buckets are collecting water from the 1) dump into the crankcase, 2) feed to the crankshaft/big-end and 3) the cambox from left to right.


By measuring the amounts of water collected over a fixed period of time I could at least compare the relative flow rates. I won't reproduce the results from this experiment here but one of the main conclusions was that the cambox flowrate only became sensitive to the tap setting when the tap was nearly closed, ie less than one turn open. I picked a value of half a turn and locked the tap on the basis that this would provide an adequate supply and I could make adjustments later.

For the rest of the final build, all the other parts are simply bolted on ….the whole process takes 3 -4 days maximum and having done a complete dry build prior to final assembly you know that every part fits properly and you’re not going to scratch the paintwork by having to modify parts. 




The first start after a complete rebuild, or in this case, a whole new engine, is always both an exciting but also a slightly tense time. Although everything has been checked and double checked there is always a possibility that something, hopefully not too significant, has been overlooked.

The first start of the AJcette was no exception. After making sure that everything turned OK, ie the engine and back wheel are connected and not going to “jam up” or some other catastrophic failure, the oil pipes are primed, the oil and fuel are turned on, one of your competent mates is with you in case anything untoward happens (it can! I once got stuck under an Ariel V-twin that I had just rebuilt and which fell over with me underneath and with my ass on the starting rollers - not going round, thankfully, and trapped under the bike with the engine running ….and nobody to help …but I’ll leave that story until another day) then it’s time to put the bike upon the starting rollers and see what happens.

The short movie below is the first start of the AJcette, which fired up immediately and sounded really crisp, but the lovely exhaust note is not really captured on the phone camera. 


The AJcette was, in fact, completed before the K7 but it wasn't long before there were 2 very similar-looking bikes in the back garden waiting for their first runs on the road.

The next stage is the shakedown. The AJcette cambox lubrication took some weeks to sort out  and how that was resolved will be detailed next.

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