Villiers F15 valve problem

I am now sure that the problems I have with my Villiers F15 is down to the inlet valve briefly sticking after the engine has turned over a few hundred revolutions although it has never been seen to do this on the bench.
Initially the only odd thing is that oil seems to have trouble reaching above the washers on the inlet side, leaving it bone dry (the breather is different to the one shown in the manual).
So I removed the valve and discovered that it may not be a Villiars valve although it has precisely the right stem diameter. The notable difference from the exhaust and also the pictures in the manual is that it has a slot in the top and it holds in place with a pin rather than a cotter.

My problem is seeing what is wrong with it!

I get the impression that the engine must have been overhauled recently as the piston bore looks perfect and the valve seats are in great condition. But there was enough carbon round the valve edges to suggest this valve has been used for a while.
The stem of the valve shows no obvious sign of wear and I cannot detect it being bent. The tappet clearance was slightly too large.

The only thing that is perhaps not perfect is that where the valve was ground to get the tappet gap right, the wear mark on this surface is distinctly off-centre. Grinding marks run straight across so this surface could have a tiny slope. Could this be the problem?

I am not sure whether to just polish up everything in the hope it will be OK again, or get a new valve and have the hassle of regrinding and grinding the length too. This project has already wasted way too much time!

If the inlet valve was sometimes sticking I think I would of run it on 2 stroke mixture for a hour or 2

In this hobby you have to dedicated and don/t let it waste you/r time

Are there any scuff marks, or burrs, on the valve stem that could be polished out?

I agree with tony; that 2 stroke mixture or a shot of Redex UCL (do they still do that; I haven't seen a Redex gun on a forecourt since I was an apprentice), is the way to go.

Your hobby should be enjoyable to you; and only seem to be a waste of time to others.

I hadn't thought of using 2-stroke, that's a really good idea.

There are some marks on the valve stem I now notice, but not much.
It would be a whole lot easier to make the old valve work reliably again than fit a new one as I am not sure I have what it takes to precision grind the length for the tappet clearance.

So maybe I will give it a really good polish and try some 2-stroke to help it along as it does seem that the splashing oil fails to reach it properly (unlike the exhaust).

I am currently held up waiting for a replacement starter cup to arrive as the old one is in a desperate state and looks hard to repair (cracks everywhere).

I keep hoping to see some really clear way it sticks. I have never seen it stick but I am confident on this as there is clear evidence of smoke blowing back through the carb and filter - and that reminded me that whenever it stopped I would see a puff of white vapour which I am now sure was all the vapourised inlet fuel being blown back out.

It is pretty clear that I am not so much fixing the engine as doing remedial work on someone else's repair (I hate that). It was not the only thing badly done by some previous owner, but the other problems were a bit easier to fix.

The problem you have got is that is like the previous owner its unlikely you will will find the original valve for your engine so have to make do with what you have or find another one, both will need fettling either way. Most engines run effectively dry as there was no way of getting oil to the stems, if you think even modern car engines dont get oil directly to them so they rely on the valve guides and valves material for a frictionless fit. Have you tried running a reamer through the guide to remove any high spots or muck. Blow back could also be the valve head being eccentric to the valve seat allowing leakage or a slightly bent valve head it wont take much.
Maryalice

Sounds to me the valve stem might be a tad too big and when it gets warm it is expanding and sticking in the guide, once it cools down it's then free to move again.

https://www.ebay.co.uk/itm/Villiers-F15-Inlet-Valve-Standard-87-2859/362102950063?hash=item544f0488af:g:0eAAAOSwNsdenF8n

May get shot down in flames here as I've never had an F15. Why not try swapping exhaust and inlet valves - assuming they are the same as most other Villiers engines?

L&S engineers keep most F15 parts, they supplied a lot of the original Villiers parts anyway. https://www.lsengineers.co.uk/vinatge-engine-villiers-f15-spares.html?p=2

Pete.

Appletop wrote:Sounds to me the valve stem might be a tad too big and when it gets warm it is expanding and sticking in the guide, once it cools down it's then free to move again.

This raises the question as to what is the correct clearance?

[quote="M0GXB"][quote="Appletop"]Sounds to me the valve stem might be a tad too big and when it gets warm it is expanding and sticking in the guide, once it cools down it's then free to move again.
[/quote]
This raises the question as to what is the correct clearance?
[/quote]

Not really as the answer is no.