sq 4 running hot

[jim.dumont]

I restored a 1950 sq 4 including overhauling the engine. the pistons are .040 over with flat tops,i don't know the compression ratio but i get 75lbs on my compression gage.The engine has lots of oil pressure,100 lbs cold and 50 lbs hot ,theres lot of oil flowing back to the oil tank. Using electronic temp gage i get reading of up to 350deg f at various places on the engine . The rocker boxes seam hot at 280f in the hotest area. Running the engine with a valve cover off shows oil comining out the holes in the rocker arms. The oil line fitting that attaches to the head has a small orfice, i am thinking of opening that orfice to allow more oil to flow thru the rockers as a way of improving cooling. Has anyone tried this mod will it help or will it cause other problems. Valve and ingition timimg are set per spec JIM

[david.anderson]

Jim
all square 4s run hot, but the least worst is the mk2. I take it yours is a mk1 and I would doubt the ability of the plunger oil pump to supply extra oil to the top end without effecting the bottom end. A Morgo oil pump may be different. The other problem you will suffer with more oil to the top end is over oiling the valve guides. My mk2 burns a bit of oil down the guides with only 5000 miles on the clock after a total rebuild. this also results in excess carbon build up. My valve clearance is still only just a working clearance, no slop. I have enquired about valve guide oil seals but have been told that they will fail rapidly due to the heat of the engine. as such I am running a steel bodied original oil pump rather than a Morgo as the extra oil pumped by the Morgo will only make the already over oiling of the top end worse.
Just a further note. I had problems stopping oil leaks from the oil line to the head at the attachment point. my remedy was to turn up new oil line fittings with a groove so that I could incorporate an O ring to stop the leaks. that works for a couple of rides before the O rings fail due to the heat.
After a couple of thousand miles on the new engine it wont run quite so hot. Or perhaps I've got used to it.
David

[brenton.roy]

Hi Jim, 100 PSI is a little on the high side - although not necessarily for a new motor. I'm not sure whether you have a Morgo or plunger pump? There is a relief valve (ball and spring) behind the cap in front of the timing cover. It might be worth checking this works ok. Oil pressure will drop as the engine runs in (and warms up). The most important thing is that oil is getting to the right places and returning to the tank.
As David says, they all run hot. We have 40+ degree days in summer and I'm investigating an oil cooler. I think at least in part it is the exhaust manifold on Mark 1's that make them (unfortunately) run hottest. For this reason, I think that after running in, the best oil you can afford, changed religiously is the way to go.
I also run a the motor a little rich - more for fear of running it lean and cooking it.
I think the Mk 1's are a great bike to ride. While they will easily sit on the highway limit, I think raising the gearing would be better at these speeds and maybe help cooling. Drags do a 40 tooth Clutch sprocket.
brenton