Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: leadnavel on May 23, 2022, 10:39:48 AM
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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.
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I'm a novice but are you sure No1 is TDC on compression reads as though its No4 just rotate the crank another turn as cam rotates at half crank speed?
Sorry if you have eliminated this possibility.
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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.
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Adding to the above, after you've done the #1 valves plus the others listed, turn the crankshaft one full rotation (notch will now be upward) and set the valves for #4 along with the remaining two not yet done.
That'll complete it for you.
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I'm a novice but are you sure No1 is TDC on compression reads as though its No4 just rotate the crank another turn as cam rotates at half crank speed?
Sorry if you have eliminated this possibility.
When I turn on the crankshaft clockwise towards the “T”1.4 mark, the key groove is towards the top of the cam index line, I look at the exhaust valve on No.1 cylinder which is just closing, the “T” arrives at the timing mark, both INLET & EXHAUST are closed. Immediately I continue turning the crankshaft clockwise away from the “T”1.4 mark the INLET valve on No.1 cylinder starts to open.
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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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Thanks for you assistance guys, thanks for taking the time to help me out. I was able to have a tinker this evening and i'm now able to set the valve clearances, perfect. I was indeed getting pre occupied with the key/notch on the end of the camshaft! Now it's on to priming of the oilways prior to the initial start-up, now that's a whole another story, requests for assistance will probably be posted soon. Cheers
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Oil pressure initially from rebuilding;- take off oil filter, remove spark plugs, look into small hole in oil filter housing with a torch (not the central hole for bolt) spin engine until oil is present in the small hole, refit filter then spin for oil pressure.
Then check oil arrives at BOTH sides of head to oil camshaft either side of cam chain.
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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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The assembly lubrication seals the bearings very effectively and air locks the system, preventing the pressure side of the oil pump from accepting the oil feed from tank. It just spins and does nothing.
Take the oil filter off (this stops the airlock from happening) turn pump by whichever method you want and watch for oil coming towards filter housing (all the pressure side has to go through this route to important bearings) as soon as you see oil present there, then the pump is primed.
Filter back on and it'll deliver everything else from then onwards.
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Thanks K2-K6, the engine is on the bench, would using the kick by hand be enough to circulate the oil?
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Yes it should do that fine with kickstart, it's just getting the oil through the pump head that's stopping it.
It shouldn't take that much to see the oil like that and once the pump has no air in it, it can easily pressure the rest of the system without problem.
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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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Have you got the oil pressure switch fitted?
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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.
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(https://uploads.tapatalk-cdn.com/20220525/846fb7e0edd2a5af0e94a3d9c1de22a2.jpg)
Yes NJ I’ve got it set up like this, any ideas what I can try next?
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(https://uploads.tapatalk-cdn.com/20220525/846fb7e0edd2a5af0e94a3d9c1de22a2.jpg)
Yes NJ I’ve got it set up like this, any ideas what I can try next?
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I'm not clever enough to know if the pipe to the gauge may be causing the pressure not to build. I'm thinking that as long as the hole is plugged, you should get pressure but maybe someone can confirm this. I'm only saying this because a forum member spent 2 weeks trying to get oil circulation after rebuilding his 750 K0 then he reliased he hadn't fitted the oil pressure switch so there was a big hole letting the pressure out 😂😂😂😂
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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?
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Looking at bike from the side, outer one is return line going to tank.
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In my next session I’ll remove the oil pipe to see if there’s a problem with that. I’ll also swap the oil pressure gauge (it does have a mighty long tube) for the oil pressure gauge to see if that’s causing a problem.
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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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Something definitely odd there, it shouldn't need so much spinning to get any output.
The scavenge side is obviously fine (different segment of pump) and should outstrip the pressure side always by design capacity (else all the oil would end up in the sump when running) so ok there.
I'd definitely check supply of oil to the pump before turning the engine any more without oil supply.
The pressure guage won't make any difference if there's no oil. It all has to go to the filter first (through that delivery pipe to filter housing) to get to any components, there's no other route. Not worth putting the filter on until you see oil present in that delivery route as nothing else will be supplied.
Without the oil pump fitted, the oil tank content should run through the supply pipe and out the hole the oil pump fits to.
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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?
Did you strip the "leak stopper" valve in the oil pump ? as this could give a problem.
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I’ve got two pumps, I’ve stripped and replaced seals and rings in both of them but not the springs as they A. They looked and felt ok and B. I couldn’t get hold of any. I bought a secondhand pump because on the strip down of my original pump the rotors looked overly marked but I have subsequently done some research on the rotors and found that the marking are pretty standard and I could’ve used my original. If the pipes look ok I’ll remove the pump and double check everything.
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I don't know if this helps but I think the info on this thread might be related. I recalled something about using vaseline to overcome airlocks in 750 oil pumps. Also might be better in a new thread as this one has moved onto a new topic.
http://www.sohc.co.uk/index.php/topic,23297.msg218481.html#msg218481
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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.
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Wish I'd seen this post earlier - I had problems on the 1st of 3 750 rebuilds I've done but on the subsequent 2 used the vaseline method and oil presure almost instantly