Unknown Barrel, Head & Piston

[IanCordes]

Now then Oh learned ones, what have we here? I am not aware of ever seeing one of these before (not that that means much!) Fitted onto a 9E/32A bottom end in a 1960 TCS. I am guessing at a period after-market conversion. As you will see it has a centre plug head, with a top-hat combustion chamber; also a domed 66mm piston. 2 x transfer ports, with what appears to be a standard Greeves exhaust. Obviously the Concentric is a later fitment.

So, what is it?

[John Wakefield]

Vale-Onslow barrel with possibly a Hogan head?

[rarpos7]

This looks very like a DKW head and barrel. I have one on a 125cc machine. Did they make a bigger size?

[John Wakefield]

Cylinder is definitely Vale Onslow (see attached pic with a VO head) Not sure about the head. DKW unlikely as stud spacing would be metric. Again possibly Hogan (who made central plug high comp heads for various two strokes, mainly BSA Bantams.

[John Wakefield]

Here is another pic (from Flickr) of the VO conversion in a Greeves (John Runnicles bike I believe) this one has a central plug head (apparently they made two types, one with decompressor and side plug, and one (as in Johns bike) with a central plug head.

[johnrunnacles]

Yep, that was my bike. Thanks for photo, John. Vale Onslow barrel as stated, and with domed piston as mentioned by Ian. Bike is now with young Charlie, last year's Hawkstone champ in the Dave Harper Championship.

[IanCordes]

Thanks gents. I would agree with you John & John, Vale-Onslow barrel. The head is a bit of a mystery, as it doesn't look as though it fits! It does, obviously...Yours looks much neater though, John R.! Interestingly, yours is in a scrambler, John, whilst mine is in a Scottish.

Can anyone give me any history on them? Were they late '50's, in order as John W. said, to uprate the 9E to 250cc? I am surprised they didn't do them in ali, as Greeves and others did. Did they have any advantages, or disadvantages, compared with other makes, or indeed the 31A/33A top-ends when they came out?
I am wondering if the head was just what the PO had to hand. Where it mates to the barrel, there is a very slight raised spigot on the barrel, which has an o.d. of 78mm, so 6mm thick. I can't imagine it is a liner, given it is an iron barrel. The initial shallow recess in the head is 66.5mm diameter, so does not drop over the spigot. It thus leaves just a 6mm wide ring as a mating surface, the outside of which virtually reaches the bolt holes. At present there is a Villiers ali gasket fitted, with the 4 corners cut off where they go around the stud holes. My concern is that tightening down could distort the head quite easily. I haven't checked it for flatness yet.

Any thoughts on machining a very shallow recess 6mm wide in the head, allowing it to drop over the barrel spigot, providing a gasket-less mating surface? It will raise the compression a bit.

Another thing puzzling me is that, with a straight edge across the top of the barrel, the measurement down to a point on the crankcase is 4.8". The same measurement off a 33A engine I have on the bench is 5.6", and that is a short rod motor. 0.8", or approx. 20mm difference is massive. The barrel will be coming off today to see what is inside; a short stroke crank perhaps?

All thoughts & comments appreciated.

Ian

[johnrunnacles]

Interesting indeed, Ian. I no longer have mine to hand to make comparisons so will need to depend on memory, but suffice it to say that the barrel enabled a straight conversion of the short-stroke 9E (197cc) to a full 250cc, albeit still using the short con-rod.

The difference in height of the barrels to which you refer is probably due to the different height of the piston crown above the gudgeon pin, a lesser height on the VO piston than on a Villiers piston.

The head on my scrambler sat immediately on the raised spigot to which you refer with never any problem of distortion arising, just needed to be careful (and gentle) with the torque settings on the head bolts.

One difference I think I can see between your barrel and mine is in the angle of the carb manifold. Mine had quite a steep down-draught whereas yours appears to be more flat. Perhaps there were different barrels available for trials and for "racing" purposes?

I believe the Vale Onslow conversions dated to about 1958. An advantage over alloy from point of view of Greeves Championship rules was that it still left the bike qualifying for "iron-barrelled" status, although giving the performance boost normally only coming from use of an alloy conversion.

Hope this helps? Adrian also runs a Hawkstone with VO top-half so may be able to add, or perhaps Charlie can give more details of my old set-up?

JR

[John Wakefield]

The first VO conversions were on the 8E and in fact the first pic I put up is on an 8E, so would have originated in the late 1950's. The conversion was the brain child of Len Vale Onslow, the legendary bike shop owner & indeed motor cycle manufacturer, he made his own Vale Onslow bike.
The conversion provided a full 250 conversion to the 197cc 8E and 9E Villiers engines. It was not till later that Villiers brought ot their full 250 32A and 34A (scrambles) engines.
To my knowledge these were only made for scrambles use,(hence the Amal carb flange mounting) I dont think there was a trials version

[IanCordes]

Interesting stuff gents. Good info; thank you. I will remove the barrel later and check what you say about gudgeon pin height to piston crown John R. That raises the issue that, if a new piston is required at any time, a Villiers one will not do, so are these still available?

Did you use a gasket, or just lap them? Any sealant used?

Now for the head! I have never heard of Hogan heads. It really doesn't look right on there, but no reason why it shouldn't work. More information on that would be gratefully received.

Thanks again.

Ian

[John Wakefield]

John Hogan was a well known tuner mainly in Bantam racing circles http://bsabantamracing.editboard.com/t928-hogan-bantam

[johnrunnacles]

Think you may have a problem finding a piston, Ian. I have just parted with my only spare one to a good friend.

My VO head didn't use a gasket nor sealant.

I was once told the head on mine was of Todd manufacture. Karting fraternity probably know more about them ? I hadn't previously heard of Hogan either. Thanks for sight of article, John.

Take care.

JR

[John Wakefield]

Adrian Dickerson may have some pistons according to this thread https://www.greeves-riders.org.uk/fo...iston-required Also I read on another forum that Simon Bateman has some, but not sure how long ago that was!!

[PeterJGreig]

I hesitate to add anything amongst all you experts, but as I remember from when I ran a 9E engine the barrel from the Invacar engine used the short rod so would fit straight on (making it a 31A I think) and were readily available from the scrap yard over the North Circ. from the Ace café- back when a cup of tea was still 6d.

[johnrunnacles]

Just so, Peter. I have (somewhere?) an aluminium spacer that fits under the barrel so that the 31A barrel can be used with the longer con-rod. 31A was standard ware on the production 24TAS and 24SAS, of course.