Oil pressure issue / motor rebuild

[Trigger]

I think you time machine to get part number 12020-300-305 Ash

Just buy quad rings . in Viton

Yes Ash, but will not fit the OEM head gasket that CMS sell 

[AshimotoK0]

Use later gasket part of NB gasket set or I know a sandcast guru who just used 'O'rings from RS. He fitted this arrangement on the 750K1 that UK Pete got off him, prior to selling him it . He did tell me the RS part number in an email somewhere. Will have to ask Pete if it panned out OK ITO oil leaks/head sealing.

[Greebo]

Another very good tip for anyone doing a rebuild, or just doing any head work.

The genuine Honda rubber "O" rings in the head that create the oil seal were found to be to thin, hence many of these bikes had leaks from the head...to stop this happening you can buy the same Diameter O rings that are slightly thicker [1mm]
So that when you torque the head down it does create a proper seal where as the stock O rings did not , this was a fault Honda never cured or modified.

If you use a O ring 1mm thicker it will not fit in the recess or the hole in the gasket as it is a 16mm hole. The OEM O ring is 11ID x 2.4mm, 1mm thicker will give you a overall measurement of 17.8mm

Well it worked on mine, & if I remember right Steve the bike builder who specialises in rebuilding the sohc engines, he  bought the washers from a local shop that supplies O rings for all sorts of applications, he said they are the same diameter as stock but slightly thicker/deeper, I am sure he said 1mm...any how he has never had a engine back with an oil leak from the head or anywhere else....

[AshimotoK0]

There is an obvious split between people on forums. As such I am deffo in the 'hobbyist' camp so don't take anything I post as here being gospel or always personally tried and tested. All I can say is that where bikes are concerned & not being in the 'trade'  ... I have NO trade  secrets. If I have any info,tips, cheapo sources etc I will share on here 100%, as I don't earn my living from it (thank God).

[MrDavo]

Get a room you guys, or an O ring thread 

Anyhoo, I used the O rings from the Athena gasket set, they seemed to fit fine, we'll see when I get her running, though.

Here's the motor on the bench, ready to rock, shiny cam cover looking good. Apologies for the Murkovision, the inside of the phone lens gets dusty in my pocket somehow, I sent it away to get cleaned a while back, but its getting foggy again. I have proper cameras, but tend to keep them away from oily fingers.



After Leigh and Ed turned up, we chucked it in and checked the dates we had written on the wall, on August 3rd when it came out, predicting when it would go back, Leigh's was 3 October, I was 1 December and Ed was 1 January 2017, so I win. Leigh accused me of sitting on my hands until victory was assured.

[Nurse Julie]

Looking lovely, well done.

[MrDavo]

I'm confused. How much turning over is necessary to fill the oil filter up from empty?

I fitted the oil tank & hoses, and put some oil in the tank. Many kicks later and a couple of spins of the starter, no oil had made it up as far as the gallery, never mind the oil light going out. I dropped the sump and the oil I'd just put in, and reprimed the oil pump. All appears fine with the pump, I don't really see how I could put it together wrong - (unless you know different- Trigger?).

Refitted, refilled, still nothing.

Maybe I'm being impatient, it's a big filter housing and tiny chambers on the feed side of the pump, but I'm paranoid about turning a dry motor over too much. Will I only get pressure when I start her up?

ETA: I found a similar thread on dot net, it turned out OK in the end. http://forums.sohc4.net/index.php/topic,101556.0.html

[Trigger]

These are a bugger to get all the air out of the system. I find filling the pump with Vaseline works as a very good prime. I would not try to push the button just yet, keep kicking it. When you built the engine back up, I hope you used Graphogen or the equivalent.
Another good trick is to take the oil pressure switch out and with a little funnel, fill it with oil.

[K2-K6]

Even when you work on them normally in servicing them after the filter is changed and you've filled the oil tank with new oil, then you can see the tank level drop by something like the volume of the filter and that's without any of the engine galleries being empty.

It's a big worry with any engine if it doesn't appear to be building pressure, and always a bit of a nail biter as to whether to continue turning over or investigate.

All things being in place it still takes longer than your thinking allows you to be comfortable with.

I always use (as Trigger states above)  Graphogen for all plain bearings when building an engine,  the principal difference from just oil is that is stays coated on the surfaces even if there is a long period between building and using the motor. It will prevent any pickup with the bearings until the oil arrives.

Presume you have the spark plugs out to reduce crank loading? 

Could try tipping on its side to fill the gallery via the plug with oil. I've never tried on one of these but you could also raise the rear and fill the oil filter housing without oil also and bolt it back on with it filled as much as possible and the filter as level an you can get it.

[Spitfire]

I had the same problems with mine after a top end rebuild http://www.sohc.co.uk/index.php/topic,1573.msg1729.html#msg1729
This was what I said at the time:
Took a long time to get the oil pressure light off, I put one litre of oil in the tank and one litre in the cam cover, it took a long time for the oil light to go out, so long that I started to suspect the oil pressure switch, but a look into the cam cover showed no sign of oil spraying around so I carried on. The oil light eventually went out, then I waited a few more minutes turning her over until I could see oil spraying about in the cam cover. Plugs in and she fired up on the second push of the button.

Cheers

Dennis

[MrDavo]

Judging by the many threads on here and dotnet, it seems we all go through this worrying dilemma every time a CB750 is rebuilt. If we couldn't see we wouldn't worry about it. None of these threads ends with an expensive clank, so it looks as if ! Once I get carbs and pipes back on, I just have to start her up and anxiously wait for the red light to go off.

I did use assembly lube, I'm glad I did now, I just never thought it would take so many turns before oil came into sight.

[Trigger]

As I said, do not push the button. Even if the oil light goes out, this may mean that there is no oil to the top end, as the switch is at the bottom and not the top. You need to remove the tappet covers to see the oil at the cam first. There is a member on here that did fire start you bastard in to the carbs and press the button until he realised that the oil had not circulated the engine and the engine was toast >>> http://www.sohc.co.uk/index.php/topic,10867.0.html

Two out of ten engines that arrive in my workshop are damaged due to oil not circulating after the owner has built the engine. So keep kicking unless you know that you have not left a O ring out and the pump is working 100%, and all your oil ways are clear.

[MrDavo]

Hmm, I am sure but I'll keep kicking, when is enough though? One wonders how many kicks is a filter full?

Maybe I should have opened the stopper valve when I primed the pump, otherwise how does it get that first 'glug' ?

[royhall]

It takes a good while doing it on the starter before you see oil at the cam so kicking will take forever. Take your cam access caps off and keep the cam lobes lubricated with an oil can. Then just keep kicking.

[Trigger]

If the cam has lube on it. I can't see the point in putting oil on it. It would be hard to see if oil has reached the top end.