Oil burning problem and trying to understand the risk areas

[Nicko]

Hello,

Working through oil burning problems on my 447 engine and searched the website for an answer to the question below without luck and wondering if someone can help?
The 4 outside main head studs are I believe used to return oil, however 2 of them have location dowels at the cylinder base, which effectively blocks off the small cut away and therefore no oil can flow via these from the head down over. Is this correct or is there an internal passage I cannot see.

Any help appreciated nicko

 

[Jim]

Oil return from the head is via the cam chain tunnel. None of the studs acts as oil return. The outer 4 studs are sealed with a long hat bushing and o-ring to prevent oil getting in.

 

[Nicko]

Thanks Jim, as I had surmised, but you can probably understand my question when you look at the engineering if they pass no oil why the base drain channels and the rubber stud nut seals.

Thanks nicko

 

[Jim]

if they pass no oil why the base drain channels and the rubber stud nut seals.

The drain channels are for 'just in case' there's a leak further up the head. The seals on the hat bushes are there because the oil passages for the rocker arms is drilled, literally through the stud holes. Since that's pressurized oil, every effort is made to seal the stud hole so the oil goes where it's supposed to... the rockers and shafts, and not back down the stud hole.

 

[Nicko]

Thanks Jim,

I have gone through everything and the only place I can see oil getting into the combustion chamber at the levels it was, must have been via the cam chain tunnel, everything else has been checked. I am going to reassemble the engine with another new head gasket and go from there. Hopefully it will not smoke

Nicko

 

[Jim]

Have you checked the head and cylinder faces for flatness?

 

[Its been a long time]

Inlet valve stem seals condition?

 

[Nicko]

Sorry for taking so long to reply Jim,
bought the bike in 2023.
Checked and rebuilt engine, new valve seals and gaskets, all components were worn but still in tolerance.
Did a 1000 mls on it but it Burnt a little oil, no smoke.

2nd rebuild went for 750 kit so new pistons and barrels.
Stopped burning oil ran great, but must have been too much valve stem play as oil visible on inlet valves after standing for a few days, so it smokes for a minute on start up, but then cleared.

3rd rebuild, had head reconditioned, new valves & springs seats cut, new seals.
Smoked mainly from no1, but evident on no 2 would not clear, just kept on blowing it out mainly when revved, lost circa 400 mls of oil in 1/2 hour running

Engine currently stripped, scratching my head, I have had valve guides to cylinder head seal vacuum checked and found to be ok.

So hence my question on oil risk areas, the only place I can think it was leaking on my third rebuild is through the cam chain tunnel directly into the cylinders, any help greatly appreciated

Nicko

 

[Its been a long time]

Have you checked the head and cylinder faces for flatness?

^^^^^ This?

 

[Nicko]

Hi Jim,
Yes I did check the head with a straight edge and all seems ok, on the last build I used a copper head gasket, which I annealed before fitting, and wondered if there was a slight warp which this type of gasket could not cope with and could have caused the smoking. The rebuild before I used a composite gasket and on removing the head this gasket showed an excellent even seal with no evidence of leakage. I have over the weekend rebuilt the top end with a composite gasket and fitted the engine to the bike. I started it yesterday and it ran well but no1 still smoked, slightly less this time, but still not acceptable. I am lost what to do next and plan to take it for a ride hopefully this week to see if something beds in.

 

[Its been a long time]

Long shot, but smoking after start on the left side? Is it parked on the side stand? If yes, try parking it on the main stand and see if it still smokes on the left side after standing overnight.

 

[Nicko]

I think I need a long shot to solve this one, thanks. But I always put it on the main stand.

 

[Its been a long time]

I think I need a long shot to solve this one, thanks. But I always put it on the main stand.

Oh well, it was worth a shot. Good luck with it.

 

[AUTOMAN]

Guide to head scoring.
Oil leaks past guide/head casting due to too much interference or installed cock-eyed.

That much oil sounds like intake.

 

[Nicko]

Thanks again for the input.
Re auto man comments, can you please expand a little on the intake theory

 

[AUTOMAN]

Thanks again for the input.
Re auto man comments, can you please expand a little on the intake theory

When pressing guides in, like a scored piston that was too tight, the guide can gall the aluminum going in.
This creates a gouge, right down the guide bore, in the head.
On intakes, vacuum from the intake port suck oil in.
On the exhausts, oil drips through when not running.
Restarting is a puff of blue smoke.

 

[Jim]

When pressing guides in, like a scored piston that was too tight, the guide can gall the aluminum going in.
This creates a gouge, right down the guide bore, in the head.
On intakes, vacuum from the intake port suck oil in.
On the exhausts, oil drips through when not running.
Restarting is a puff of blue smoke.

Our XS guides go in with an o-ring under the shoulder. Provided it's installed correctly that is.

 

[Nicko]

Thanks automan for the comprehensive reply, prior to my last rebuild that was my strong theory that the oil was seeping past the guide/ head joint, but following removal of the head I had the guides vacuum tested and they were passed as not leaking.

 

[AUTOMAN]

Don't count on vac test to test such a small leak, cold.
Heated, may open up even more.

It takes little oil to make alot of smoke.

 

[Nicko]

Don't count on vac test to test such a small leak, cold.
Heated, may open up even more.

It takes little oil to make alot of smoke.

Thanks, automan
I have had clean white cloths pushed in through the spark plug holes, no sign of oil.
So
I started the bike again yesterday and no smoke for about 5 seconds, this would indicate it’s being pulled in from somewhere. (Only no 1 smokes)

I agree, I always suspected the guide/ head seal, so I am going to do the following:-
Start the bike for 5 minutes, remove no 1 plug lead and keep it running for 10 minutes, raising the revs occasionally. Let it cool a while then Remove no 1 exhaust's and check for oil, if none found rem carbs and check inlet. If nothing found observe guides for a couple of days and watch for signs of oil.
What are your thoughts?