After a bit of popping and farting, deciding it was not the lack of dietry restraint I usually have ( ie curried breakfast ) but the valve seats on the Red Mullet, were pitted and black led me to consider that the unleaded we are now getting is a lot more caustic that it used to be- as my M63 always got on fine with previous unleaded over the years......but at some point, your Ural or Dnepr will need a cylinder head off to correct a valve fault....like not having one.....so this may be of assistance.
You will be familiar with taking a valve out and lathering it with grit paste and grinding away until you are fed-up with it.....but this is not the truth of the matter. After some time, valves get 'pocketed' in their seats, as the seat wears and the excessive grinding gives the seat a bowl aspect. This restricts the free flow of gas in and out of the valve orifice- You can correct this with a couple of simple and cheap tools- remember you saw this here !
The next illustration shows two seat cutting tools, a Ural valve and the peice of tubing used to support the cylinder head on the table of the drill press.
The flaring tool is a lump of alloy secured to a 5/16" mild steel rod with an M4 screw, a second screw holds a TCT lathe tip at @60-70 degree angle, when in the valve guide. The brass tool is a solid bar machined to fit the chuck and the valve guide, with a peice of tool steel ( an old center drill bit ) ground to 45 degree-to cut the valve-seat -matching it with the valves seat face. Use this if you have just fitted new guides, as the old seat position will not be concentric with the new guide.
The cardboard washer stops swarf falling down the valve guide, as it cuts.All these simple materials can be found online at www.chronos.ltd.uk, who supply model engineering stuff.
Smear the valve with engineers blue and put it in the head, twiddle it to mark out the actual valve seat contact point-this will show you where to cut down to with the flaring tool.
This is known as fly-cutting, it is a bit noisy but take your time and only remove a little metal before checking the valve seat with blue engineers marker, it will get you there, with patience.
Finished seat ( Below ) showing valve seat width ( in blue marker ) which should be no wider that the thickness of your thumb-nail. This will give maximum seat pressure and good sealing of the valve.
A Ural head is symetrical front to back, if you mount it in a milling machine, you can mill out a recess for a second sparkplug that corresponds to the original plug position. Beware of the oil drain channel though, it is easy to mill through this ( as I did) then tap it to take a spark plug. Now with your two TWO plug heads fitted, you need two twin spark coils fitted to the bike ( I used some off a 4 cylinder Kawasaki), the positive ends of the coils are wired together to the original connection and the two negative or CB ends are wired to the points, so that the coils are running in parallel, use as big a condenser as possible as the points are now switching twice the current.
The image shows the head of an M63.
You'll find that the emissions improve, starting improves, torque increases and you can even jet the carb down a bit, although thats getting carried away, as maybe I should be.....
AND I nearly forgot............no-one knows how to anneal ( soften) aluminium head gaskets, do they ! You cannot tell the temperature of the metal until it vanishes in a pool of alloy under your blowtorch !
Well, little ones, just sprinkle sawdust or old cocktail sticks on the gasket, heat from underneath until the wood starts to char and there you are a lovely soft gasket again....................
