Valve guide seals for early 750 twins

Pull the plug.
With the piston up close to TDC, take a length of ~5/16 diameter cord and feed it into the sparkplug hole till the chamber is full (leave a length to pull out the cord.) The purpose of this is to keep the valves from dropping into the cylinder which would mean you have to pull the head.
Pull the valve cover, remove the valve keeper and springs, remove and replace the seals. Reassemble. Adjust the valves.
.006 int/ .008 exhaust. Install valve cover. Pull out cord.
Replace the plug.
Don't nut up over the cord thing. Kart racers use that technique all the time.

depends on how the head was reconditioned
were new valve guides installed along with new valves
were the stem seals correctly fitted
was a compression test done to determine the wear condition of the engine
smoke on start up is oil in the combustion chamber from valve stem seals , worn rings , sump pressure from excessive blow by through the line to the air inlet
check for oil leaks ( filter etc ) but using a lot of oil indicates ring problem, excessive bearing clearance overloading the oil control ring
try using a heavier grade of oil 30w 50 or oil for worn motors

Neither. Check the valve guides and valve guide seals.

remove the rocker cover and remove the cam shafts then fit new seals , get a good work shop manual for step by step guide

the dynamo dishwashing stuff has caused foaming which reached the base of the dishdrawer unit causing the flood switch to trip. This gives F1 error.
Not sure how much foaming has occured.

Best to turn off power and take power cable out from socket. then empty the drawer using towels. pull out the bottom drawer and wait a day or so to let the foam disappear from the bottom of dishwasher (under the bottom drawer). Connect the power and see if F1 had gone. If not, you need more work. Post a comment based on the above suggestion and I will guide you further if required. Always use Finish dishwasher power only (recommended quantity) as the drawers are small and don't need much detergent.

Check the mating surface where the head meets the cylinder. Bad oil stains on the cooling fins in this area would suggest a bad head gasket. Do a compression check. Chances are the rings are bad or frozen to the piston from a long period of storage. In any event, the head would need to come off for a repair. So go ahead and stick in new valve guide seals and have the valves re-seated.

Oil in the cylinders mean worn rings or worn valve stem seals. You can try a blow down test to see if it is rings - get an old spark plug and bust out the ceramic weld in a fitting to press with air and air up the cyl. if you here air in the crankcase you have worn rings. You just have to replace the valve guide seals no test there. 

This is a vary commom problem with an Intek engine, I have a similar 21HP engine with similar issue. The valve is sticking in the valve guide, the valve guide usually slides in or out. If out, the guide can jamb against the keepers and not allow full valve opening, thus bending the rod. Fix the loose guide and tight valve before you put in another rod, or you will soon be putting more rods in. I think B&S should help everyone on this one. If the guide goes in, it can cause the valve not to close fully and cause a no run condition.

Per previous post. A quart in 750 miles would be extremely high.  A Porsche 930 Turbo Carrera driven hard doesn't use this much unless it's motor is toast, and it is practically a race car.  You should expect at most a quart of oil consumption for 3000 miles.  A quart of oil in 750 miles is a quart EVERY OTHER tank of fuel, and would indicate a motor that needed a rebuild long ago (or seals, guides or rings).  BTW, If you can see smoke in the read view, it looks much worse when someone is driing behind you.  STP or changing to the next higher weight of oil are short term solutions that may help you not leave a trail of smoke.
If you need valve seals, maybe that's it,  but if you need guides, the rings are probably near shot too, unless there are extenuating circumstances.
cheers,

That is usually a sign of worn valve stems/guides or seals.
When you take your foot off the accelerator going down hill you effectively close the throttle, the vacuum pressure created in the inlet manifold will open the throttle slightly and the vacuum will look for "inlet" from anywhere it can and one of these places is down the sides of worn valve stems/guides, it will **** a small amount of oil down the valve guide and the oil burning off when you put your foot back on the accelerator is the smoke you see out of the exhaust.