18. BSA A10 The Generation Game

The continuing saga of the BSA A10 Super Rocket rebuild. Time to look at the dynamo, I had removed the dynamo back in February 2012 and it had sat in a draw in my workshop ever since. Stripping it was not too difficult but the inside revealed the usual signs of old age along with large quantities of oil. I can only assume that with the bike standing still for so long, the oil tank had slowly emptied itself into the sump (known as "wet sumping") and then when eventually the previous owner had got the bike running the oil was forced past the old oil seals and into the dynamo. Needless to say the coil was soaked along with the armature and the brush gear. I stripped it down completely and inspected each part and then contacted a chap who advertises himself in the BSA Star magazine as "Dynamo Dynamo". He was extremely helpful and advised me on what parts I needed and the costs. Basically I replaced everything except the armature and the body.

Once I received the parts, I selected all of the items that could be seen on the outside, including the main body and the brush gear cover and sent them away for chroming. I then set about polishing the aluminium end caps and cleaning up everything else.

Sometime later the chromed parts arrived back and I set about reassembling the dynamo. The idea was first to do a "dry build", just to see that everything fitted and that nothing was missing. This turned out to be a good idea, as as soon as the coil and the armature were bolted in place, it was obvious that the armature would not turn and was fouling on the coil. I spoke to the Dynamo man and he informed me that you needed a special tool to tighten the coil in place, but that also sometimes you just needed a slimmer coil. After due consideration, I decided to send the whole thing back to him for reassembly. I've learnt that sometimes the secret of DIY is knowing when not to!

The reassembled dynamo arrived back a week later and was perfect. Time to offer it onto the engine. I fed it through the dynamo clamp OK and with its new cork seal in place it fit nicely up against the back of the inner timing cover. Time to go into the draw and pull out the dynamo drive sprockets. For those of you you are following this blog, you may recall that on my 1st December blog I said that the eagle eyed BSA experts would notice that something was missing from the inner timing cover picture. It was at this point that I found it. Laying in the draw was a strange steel bush with two holes in it and a large flange. I had no idea what it was, but it looked important. All sorts of warning bells were ringing, had I got to strip the whole engine again?. I worked my way through the parts book until I found it. It's called the camshaft oil breather and it fits on top of the cork pad on the end of the camshaft, located by the peg that sticks through the cork pad and through the inner timing cover from the inside.

This meant removing the inner timing cover again along with the oil pump and tacho drive and of course a new gasket. The other thing that happens as you remove the inner cover is that the centre timing gear comes off with it and the valve timing is lost. So I reset the valve timing fitted the oil breather, checked the end float, fitted a new gasket and reassembled.

Now at last I can fit the dynamo sprockets, along with another cork spacer behind the big one and then the drive chain around the two sprockets. It was then simply a case of rotating the dynamo to tighten the chain. A hard press on the dynamo to make sure that the cork gasket seals against the back of the inner timing cover and tighten the dynamo clamp. Now the oil pump and tacho drive can be refitted and at last the outer timing cover fitted.

This final picture shows the rebuild a little further on with the exhausts fitted, but I'll cover that on another blog.

For those of you who follow this blog, you will have noticed that there has been a gap of about 6 weeks since the last one. This was due to the decision to buy a box trailer to transport my bikes in to shows. The huge amount of work necessary to make the box trailer usable accounted for the missing progress on the A10 and will be featured in another blog later.




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 Copyright K. Hopcroft  17.02.13 All rights reserved
 You can contact me on: hopcroftscoot@gmail.com

My Other Blogs:

1961 Ariel Arrow Super Sport Motorcycle :
http://60sclassicmotorbikes.blogspot.co.uk/2014/01/1961-aerial-golden-arrow-restoration.html

Miniature Land Rover Defender:
http://miniaturelandrover.blogspot.co.uk/2016/02/1-miniature-land-rover-defender-idea.html?view=timeslide

1971 VW Karman Ghia Convertible Car:
http://karmannghiarestoration.blogspot.co.uk/2017/03/1-karmann-ghia-retoration-project.html

Motorcycle Trailers / Caravans:
http://motorcycletrailersandcaravans.blogspot.co.uk/2018/01/1-motorcycle-trailers-problem.html