Well I had a short spell to work on the bike after buying a compression tester. I did a compression check on the cold engine and came up with these numbers. The numbers seem a little sketchy to me, what do you think?
Dry: Wet(oil):
1. 90 135
2. 105 120
3. 130 130
4. 140 150
These tests were done without adjusting the valves. Which I think needs to be done but I need to buy the feelers, which I though I had. Hopefully that will improve the tests. I thought it was best to wait until I run those tests to pull the engine completely apart. Could the difference in numbers be from a bad head gasket?
Also take a look at the pictures of the top end. On the left the rocker arm pivots have drilled holes to allow oil in. However on the right the holes do not exist. Is this because of a swap from the PO? Should I be worried about this?
I was also wondering if there is anyway to pull the transmission without removing the top end? If my piston and rings are good I think it would save me time.
Any other advice would be great as I've never done this before!
Piet
For starters, there's nothing wrong with those compression numbers. The initial low numbers are just from dry bores, the oiled ones show nice results.
The rocker towers (also called cam bearings): the left one with the holes you refer to are stock style on K3 and later engines. The rocker shafts (stock ones, anyway) had threaded holes in them that line up with those holes and 4 litle 5mm bolts go into the shafts to stop them from rattling. Sadly, this also made them wear very quickly, and it cost almost a whole HP in lost torque. It was a quieting move on Honda's part, as the top ends of these bikes were rather noisy when the bike had a Vetter or Bates fairing installed: in the 1970s this composed more than half the 750s leaving the showroom floor for touring (it was the BIG touring bike in the 1970s).
The right cam tower is the K2-and-earlier style. It produces more torque, and the shaft inside lasts longer because it can spin a little with the rockers and distribute oil inside. A simple example: the typical K3-and-later rocker shafts and rockers last about 25000 miles before the shaft and rocker wears and introduces .003" extra clearance. My K2 has 130,000 miles on it and original shafts and cam towers, still has only .0018" clearance. Stock clearance was .0006" to .001" new.
My upcoming book, in the "performance" chapter, devotes a whole section to these rocker towers, shafts, and rockers, and what to do with them....
The shafts are best replaced with K1-K2 style shafts, if yours are worn. The little bolts (which are already missing in your engine) that lock the shafts belong anywhere else but in the engine. It was not a good long-term design change on Honda's part, although it did let them make looser tolerances on these parts and not suffer noisy top ends, so it was cheaper to build. It seriously shortened engine life, though, and lost significant power.
You can also make your own shafts with Thomson 12mm hardened shafting if you grind a V-groove in the center so the long middle bolt can get past the shaft while holding it in place. Honda's replacement parts are either the 2-bolt lock-down design of the K3-later, or the side-groove replacement versions for the K0-K2, neither of which rotate. The K0-K2 version can wiggle back & forth a little, which is better than the later version, but still cannot spin fully, so it won't last as long nor lube as well. It's a better part than the later one, though. See below for a mod that would make this part better...
Yo can also cut a small oiling groove around the whole shaft at each oiling hole in the rockers, which will let oil reach the tight zone on the bottom (loaded) side of the rocker: this will bring you some free HP. This groove only needs to be about .007-.010" deep, like a deep scratch, to make it work right.
