Author Topic: Problem with initial valve adjustment after rebuild  (Read 711 times)

Offline leadnavel

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Problem with initial valve adjustment after rebuild
« on: May 23, 2022, 10:39:48 AM »
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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Offline McCabe-Thiele (Ted)

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Re: Problem with initial valve adjustment after rebuild
« Reply #1 on: May 23, 2022, 10:45:30 AM »
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.
« Last Edit: May 23, 2022, 11:02:00 AM by McCabe-Thiele (Ted) »
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Re: Problem with initial valve adjustment after rebuild
« Reply #2 on: May 23, 2022, 11:13:36 AM »
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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Re: Problem with initial valve adjustment after rebuild
« Reply #3 on: May 23, 2022, 11:46:27 AM »
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.

Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #4 on: May 23, 2022, 12:12:33 PM »
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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Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #5 on: May 23, 2022, 12:13:50 PM »
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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Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #6 on: May 24, 2022, 07:22:49 PM »
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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Re: Problem with initial valve adjustment after rebuild
« Reply #7 on: May 24, 2022, 08:23:16 PM »
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.

Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #8 on: May 25, 2022, 02:23:05 PM »
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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Re: Problem with initial valve adjustment after rebuild
« Reply #9 on: May 25, 2022, 02:41:21 PM »
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.

Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #10 on: May 25, 2022, 03:08:06 PM »
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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Re: Problem with initial valve adjustment after rebuild
« Reply #11 on: May 25, 2022, 03:12:30 PM »
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.

Offline leadnavel

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Re: Problem with initial valve adjustment after rebuild
« Reply #12 on: May 25, 2022, 04:04:18 PM »
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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Offline Nurse Julie

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Re: Problem with initial valve adjustment after rebuild
« Reply #13 on: May 25, 2022, 04:20:38 PM »
Have you got the oil pressure switch fitted?
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

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Re: Problem with initial valve adjustment after rebuild
« Reply #14 on: May 25, 2022, 04:23:35 PM »
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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