Hi all...Where there differences between the 1925 to 1928 cylinder heads and valve size or valve configuration vs: the 1929-1931 model 9? OHV 500's.... Thanks, terry.
Hi
There is some information on valve sizes in the parts lists for some of the years.
It might help
http://www.sunbeamland.com/partslist/ (http://www.sunbeamland.com/partslist/)
Ok thanks for that......I have purchased the piston for the 1930. It needed to have about 1/2" taken off of the skirt of the piston as the flywheels would not swing past it....ie: it was too long below the wrist pin....
the 7/8" wrist pin opening in the piston was 1" ......it needed to be widened to about 1-1/4" as the connecting rod on my bike would not fit....regards terry.
The bike I am working on is a 1925, model 11, 500cc. The diameter of the margins on the valves that came out of the head are 1.686" so they would not have been 1-5/8" .....they must have been 1-3/4" originally. The stem tips show signs of a fair bit of dressing if they were like the valves I bought from the club recently.
The stems on the valves I have now have a higher beginning of curve where the radius at the bottom starts to flow (tulip) into the face of the valve. i.e. The stem of the new valve is wider at a higher point where it enters the guide. I will have to take about 0.200" off of the guides to set the valve in place. There is no pocketing of the heads at all. The single port head may be new.
I need to either make new guides or sleeve the ones I have for the hair spring twin port head. These guides that are in the head were made from a worn ship guide. They were reemed too large...12 thou. .....about the same clearance as the guides that came out if it!
Thanks ...terry.
Hi Terry,
It was usual at Velocette to have a recess in the valve guides (an internal diameter wider of around 5/100mm on about 3/4mm.. I think it was for avoiding some seizing. I did it on my RE CO, works well. In fact, the gap between the recess and the valve stem is covered by carbon.
Hi Claude:
Yes I have seen Norton commando guides having a recess of a larger diameter on the valve heads side.
One of the profiles of the guides the club has in stock has a profile showing a recess in its bore. Guide type 2 as per the schedule provided by Vic.
I always thought it was for the carbon buildup somehow as well..
These valves get larger very quickly at a higher point at the bottom of the stem...I will have to look carefully at the profile of the valve before modifying the guides to suit..(shorten them) ...the exhaust valve and intake valve guides are of a different profile because the bore in the head for the two guides is of a different length.... the intake guide is in the air stream as it only has a 1/2" bore so it tapers to allow flow......the exhaust is of the same length but blunt as it has a 1-1/4" bore in the head....thanks , terry.
Thank's Terry,
One more information added !