classic motorcycle forum

Hi Kiwi,
I would firstly find some local Norton / Vintage Enthuasists in you part of the World, they will know of reputable firms that will be able to sort out your engine problems without shipping them halfway round the world, get several opinions!!!!
On the Dommy engines theres a spigot on the top of the cylinder that fits into the register in the head
When the cylinders are rebored the spigot becomes very thin and often cracks around where it meets the gasket face, It can be machined completely away and then rely on the gasket only to seal the joint
This is another consideration if you are having the cylinders resleeved
Again very hard to advise with out actually seeing and measuring up,
I would firstly  try and source some secondhand cylinders that have not been bored past the recommended max oversize
Again on the head,  find people who have had sucessful repairs before commiting the work to someone
I would have the ports blast cleaned to remove any carbon stuck to the guides before trying to remove them,
The best practice is to machine away the tops of the guides so as they can be removed towards the ports
Heat the head to 220- 240 deg C before removing and replacing guides

HTH
John

Hi JBW,

However, & I may be wrong  (& I can see that in Sprinters, maybe the absence of a Rocker box would not be too much of a problem due to the  specialist short term use);  but road going models, surely, would have needed protection by Rocker Boxes, later on in their development to cut down on wear & tear & I thought I have seen them sporting rocker boxes  in historic displays.

Am I right or am I thinking of another engine?

Yes you are correct, the speedway engines and some road engines were and can be fitted with valve covers
A tin cup sits under the valve spring and a two piece alloy casting  clamps around the alloy rockerbox where the rocker exits to operate the valve
See here
http://www.500race.org/Marques/JAP.htm

Cheers
John

Hi Doug,
This may help
http://www.vintagenorton.com/2009/05/assembling-sturmey-archer-gearbox.html

Theres a prewar AJS and Matchless very active on Yahoo groups
http://groups.yahoo.com/group/wd-prewar-ajandmatchless/

Cheers
John

Hi Wetdog
I am looking for a BSA alloy engine BB or CB to go into a nice BSA rollling chassis I have
I may have some swops trades that would interest you?

Regards
John

My opinion

Hi Greaser
It probably depends what country you live in??
European norm seems to go with the frame date
HTH
John

Hi,
UC is a JAP engine prefix, 600cc
It looks as if this number has been added to your crankcase by someone
I have seen a JAP engine with that position for the sparkplug, on a V twin though
Blackburne usually have their name prominently on the crankcase, not seen one without, unless you count the "Dennis" lawnmower engine copy 
It looks to me as though the timing case and oil pump have been "home additions??? certainly on the "Sunbeam " style
I would lif the cylinder and look for a part number or name on the conrod
HTH
John