No Paul, the one-way valve in the breather hasn't solved the issue, but it has reduced it a bit.

Since my last posting I have modified the rocker oil feed so that it's now tee'd off the return to the tank. I put a small restriction in the tank side of the T-Piece to ensure flow to the rockers. I've ...

The breather is just a hole in the top fitting of the oil pump drive shaft. There is a ball bearing in it but it’s a thrust bearing, not a one-way valve as described in the handbook. Maybe earlier models had a valve.

Thanks Nev. Luckily it’s a steel pump so no worries there. I’ve never used running-in oil either but I’ve never had a KH before either!
I’ve now got the rockers fed from the return side so the original feed now just goes to the gauge, which now shows 100psi when first started up.
The biggest ...

Update: I think the oil pump is fine!

I made up a bench jig with a 'tank' and a 'sump' and drove it with a battery drill. The return flow definitely exceeds the feed flow.

Attached are images of the pump with manifold plate and tank (aerosol lid) and the unit sat in the sump (banmarie tray).

I've ...

Thanks Paul, I’ll give that a try as I have a Morgo filter in the return side. My feeling is that the rockers should get the filtered oil but yours is the simplest solution.

Steve, if I read everything correctly, you have done quite a bit to reduce smoking from the engine. I once did own two KH’s but never did experence what you are writing…
However, you mentioned new pistons and rings, which might be the cause: A: new rings take ‘ages’ to bed in due to modern oil ...

Both my KH’s gave aprox. 90psi ‘stone cold’, but once warmed up under riding conditions it stayed on aprox.65psi and idling 20-25.This was done with a mod with all oil pressure to the mains and top end oiling from a bleed of the return. The problem on the top end is caused by the fact that most ...

Hi All.
Hoping someone can shed some light on this.
My KH500 smokes as though it's wet-sumping permanently.
To side-step any answers about rocker-gear over feed, please note that my engine has all the fixes for that, i.e:
Restrictor in the rocker feed
Club tappet guides with larger drain channels ...

Hi there.

New member with a unrestored 1952 KH here. I intend to preserve it in its non-standard patinated state and I'm looking for a set of exhausts and silencers to match the condition of the rest of the bike.

I will consider anything you might have left over from your restoration or lying in a ...