Honda-SOHC

Thanks for your assistance guys it’s been a massive help. Sorry for the delay with the update I’m in the middle of a house move and the other half (we’ll the other 3/4) had other plans for me.

Long story short… I’ve got flow to the camshaft/holders and top end gubbins, the problem appeared to be an air lock.

Short story long… I disconnected the oil hoses from the oil tank (my engine is still on the bench connected to the oil tank) to have a look to see if there was a problem. There wasn’t any oil in return pipe but the feed pipe was full. I took both hoses off and blew them through, they were clear.
I removed the oil pump, all three ‘O’ rings present and correct. The ‘stopper valve’ was also working OK. I immersed the pump assembly in engine oil

Oil Pump
https://youtube.com/shorts/WYfMHacZ3iM?feature=share

Oil Leak stopper valve
https://youtube.com/shorts/D7f3qYA43BQ?feature=share

turned the sprocket by hand and saw lots of air bubbles coming from the pump feed holes. After 5 minutes of turning I did notice the bubbles had mostly stopped and I that there was more resistance when turning the sprocket. I then removed the pump assembly from the oil bath, trying not to turn it or hassle it too much then I let it sit for a while raised up above and off the screen at the bottom, about 10mins, only a small amount of oil drained out. I replaced the pump assembly and only had to kick it over 7 times before oil started to show in the hole in the oil filter housing, result!

I did toy with the idea of using Vasoline Smoothoperator when I initially serviced the oil pump but wasn’t confident I could do it correctly, in hindsight I probably should’ve gone this route.

I then fitted the clutch basket and connected an oil pressure gauge to the outlet where the oil pressure gauge is fitted and turned the engine over using the starter motor pressure came up to 40psi after about 5-10 seconds.

Pressure Test
https://youtube.com/shorts/l6NEGcQ0b0o

Thanks again guys for taking the time to offer your assistance it is really much appreciated it's gotten me a whole lot closer to finishing the project.

I was able to get back to the project yesterday and swapped the pressure gauge for the oil pressure switch, pumped the kick start a few times (50) still no oil coming through! Before I remove the oil pipes (hopefully tomorrow) from the oil tank to check those, I thought that I would try a suggestion given by Hondaman on the other place.

http://forums.sohc4.net/index.php?topic=12686.0

Basically it’s a kicking/bursting routine. Firstly using the kick start 40-50 times then a short burst of the starter for 2-3 seconds then do it a second time. I did this routine 4 times, making sure that the oil in the sump didn’t run dry, this didn’t work for me either. All that I’m still getting is the oil from the sump getting pumped back to the oil tank when kicking it over (or using the drill attachment to speed up the process) with the sump running dry.


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Worth checking basics then as it should be doing something.

First would be supply hose from tank to see if it's impeded, then remove pump to inspect internal and verify passage from feed hose down to pump.

Both oil hoses are new, the oil pump was stripped and refurbed, that's not to say that not where the problem lays though. Which of the two oil hoses is the feed and which is the return?

I took the oil filter off and used the kickstart to get the oil moving but nothing came through so I used the spare oil pump sprocket on my cordless drill to get some consistent revolutions but still nothing coming through. I keep refilling the sump with engine oil but that just gets pumped back to the oil tank.


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I’ve read numerous posts regarding problems priming the oil ways on these darlings so I thought that I’d cracked it when I came across this option on cycleexchange

“Initial Start Up of a Honda CB750 Motor After Rebuild (Oiling)”

http://www.cyclexchange.net/Tech%20Tips%20Oil%20Related.htm

All I seem to be getting when I use the drill attachment is the scavenge side of the pump emptying the sump pan and filling the oil tank, there’s no oil leaving the oil tank! No oil coming anywhere at the top end.


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It's more a foible of the manual description and giving different information for two different tasks than anything wrong.

To set the cam originally (installation) you do as you've done with mark lining across  am carrier split, and notch at 12 o'clock.  The notch is not visible for setting tappet clearance with cover on and so not really significant.

Buuuuut, setting it like you are now with it all visible,  put the camshaft notch at the bottom 6 o'clock and it will then conform to the schematic of which valves to set clearances at.

You've not got anything wrong, just how some things are explained in the text.

Thanks K2-K6 I will have a look at this this evening.


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I've been rebuilding the Engine on my 750 K7 (77) and i'm trying to set up the valve clearance, this is where i'm having the problem! When I try to set up the valve timing by the book - set the "T" mark for 1.4 with cylinder 1 at TDC and the key groove towards the top - I should be able to (if I'm reading things correctly in the workshop manual with the "O"s and "X"s diagram) set the valve clearances for INLET and EXHAUST on No.1, EXHAUST for No.2 and the INLET for No.3. This is my problem, i'm finding that I cannot set the clearance for cylinders No.2 EXHAUST and No.3 INLET as they are on the cam!


What am I doing or have I done wrong? I hope that someone out there can can advise me on what to do to put it right. I've been searching the forums but i'm either not putting the right search terms in to get a result or it's to simple an error on my part that it's not referenced! Any help that you guys could give would be muchly appreciated.

Also to note that when I rotate the crankshaft 360 to set the remaining valve clearances the same problem occurs. I can set the clearances (INLET & EXHAUST) for Cylinder No.4 but the INLET for No.2 and EXHAUST for No.3 are on cam and cannot be set!

Engine rebuild info...

My bike had previously been running. On strip down I backed off all the adjusters so I didn't have a reference from them as to where the adjusters should be. I bagged and tagged everything. Is it possible that I tagged some rocker arms incorrectly, could I have put them back in the wrong place?

When installing my camshaft/cam sprocket on the top end rebuild I had No.1 and No.4 cylinders to top-dead-centre (TDC) and aligned the "T" mark on the spark advancer also aligning the Timing index line so it was parallel to the top surface of the camshaft holder with the key groove was towards the top, so i'm thinking that I did everything correctly with the camshaft installation.

I have a quandary, do I leave things how they are or do I flip the rotors to the workshop manual orientation?

On stripping down the oil pump on my 750K7 to renew the seal and O-rings I noticed that the rotors have been installed the wrong way up NB: when taking off the end cover of the rotor the ‘punch marks’ are not visible, they are on the underside and facing downwards!

This is where things get a bit more confusing, I was hoping for more clarity when I bought a second oil pump.

The rotor surfaces on my oil pump looked a bit marked/scored so not knowing if this was serious (I have subsequently found out that the light scoring on the my original rotors isn’t terminal so I will use my original pump) I bought a second hand K7 pump, primarily as a replacement and potentially for spares. I have stripped the pump and if a spare is not required will rebuild to sell on. On stripping down this second pump I also found that the rotors have also been installed with the ‘punch marks’ downward!

This is my quandary, on reassembly should I leave things as they are and insert the rotors ‘punch marks’ downwards or flip them and install as per the manual? My workshop manual does mention the the punch marks it says “Install the rotors with the puntch mark facing to the outside”. My Haynes manual does not mention punch marks on rotors at all.

My bike has 36'000 Miles on it and was working fine before strip down, although, FYI, the bike has been off the road since 1985, the engine strip down was started in 2019. I don’t know the history of the replacement pump.

Any advice on this would be welcome.