Oil filter housing O Ring keeps blowing out

[Oddjob]

Just looking at the picture of your engine Johnny.

Just some words of advice learned through many years of owning one of these bikes. Fitting a socket bolt into the gear lever pinch bolt area doesn't work. They can't exert enough force to really clamp the lever to the shaft without them rounding out. The result is they either vibrate loose and fall out on a ride or the lever starts to slip, causing the splines on either the shaft or the lever or both to round off. Result, new lever or shaft or both. The other thing that happens is the the hole in the top fills with water, all those socket screws facing upwards will suffer from this. They may be stainless but they will rust, when you go to remove them some years later you find they round off before letting go, with the shape of those button head you have no grip for any mole grips etc. Drilling stainless is hard so drilling them out will be very difficult. If you don't like the standard JIS casing screws (and I don't) then fit some of the modern Honda 8mm headed bolts instead. They look better, perform better and are readily available at not a great cost. There is a detailed post on part numbers for these bolts on the site.


In the gear lever fit a stainless steel 20mm bolt there as fitted as standard. With a washer under the head or you'll mark the chrome tightening it up. Try Middletons for stainless steel bolts, they aren't marked on the head and come ready polished. Do the starter motor cover ones at the same time, get lengths from a parts book.

As I said, just some advise, you can ignore it if you wish.

[Johny Boy]

Thanks for that, I will take that on board, especially as I'm currently taking the engine out.

Thanks for the previous post showing the relief valve set up, mine was like this.
Also to answer an earlier post, the bypass is internal to the pump, when open it feeds oil back to the low pressure side, you can just about see the path on the attached photo. [ Guests cannot view attachments ]

[Bryanj]

If it bypasses to the intake it cant be moving enough to allow bypass

[Ken4004]

Hi badger, yes they have been vapour blasted and they do look brand new, well worth the money if doing a full rebuild.

You raise a good point, I did give them an extra wash but now really wishing I had blasted some 6 bar air down every hole, which I can't guarantee I did.

If I can't find the issue with the relief valve, a full strip and clean might be necessary.
From what I read the relief valve should open about 60 psi, roughly 4 bar so I am going to investigate and then see if I can get it to move with some air pressure.

I had my cb400 4 engine vapour blasted, expensive but really looks like new when finished and in my opinion well worth it.
The guy who blasted mine never reused blast medium so the finish was totally uniform all over the engine.

While I was there he showed me a brass engine casing from an old car he had just finished and it looked like a piece of gold .
I did um and ah about the cost but thought just go for it and I wasn’t disappointed.

[McCabe-Thiele (Ted)]

If it bypasses to the intake it cant be moving enough to allow bypass

The oil path will only be open to the intake when the valve is opened by the valve, due to  excess oil pressure.

[scottly]

Old / wrong Spring fitted? It seems to fit and an old spring should get softer as it ages meaning lower relief pressure.

I ran across this on the US forum today. Might be worth a read?
https://forums.sohc4.net/index.php/topic,192531.msg2244067.html#msg2244067

[Johny Boy]

Old / wrong Spring fitted? It seems to fit and an old spring should get softer as it ages meaning lower relief pressure.

I ran across this on the US forum today. Might be worth a read?
https://forums.sohc4.net/index.php/topic,192531.msg2244067.html#msg2244067

That is interesting, I will measure mine up, after checking 550 / 750 share same spring.
I checked on David silver spares, they don't do it anymore but I think cmsnl do.
Will get a replacement as I'm doing a full strip down anyway

[Bryanj]

Yes just checked at cms and both spring and plunger for 500 have 300 middle number so 750 parts