Website blurb on Model 88

Previously bruce_kirby wrote:

Not sure if this has been raised in the past, so apologies if it has in advance.

I note that under the "Models" tab, the dialogue w.r.t. the Domi 88 indicates that from 1954 on the 88 had a welded on sub-frame. IMHO '54 Model 88's still had the bolt-on sub-frame.

Well mine does anyway.......

Bruce

On a similar note I have a '53 88 engine in a box of parts along with an alloy head which I understand from that same write-up didn't appear on the 88 until '55. Is there any way to tell what model a head came from?

Bruce too.

Like many details about the early 1950s Nortons there are facts and hidden truths.

After sending off the first batch of Model 7s as exports to far away countries, there was a slight pause in production while the over-heating problems with the early cast iron heads were sorted. This basically involved re- casting the head to have a better air flow across the carb manifold which itself was now a separate item. The Mk 1 head having an integral head and manifold. See attached diagram.

The Mk 2 head was far better but still got hot and bothered when used for racing. So the factory had a batch of heads cast in alloy and used them on their official 1950 International Six Day Trial bikes. Reported by The Motor Cycle in August of that year.

From then on these heads were also made available, as an option to selected private individuals. Not all for racing purposes. The factory records indicate that a few exported 500cc Twin Featherbed bikes had Manx frames and Alloy heads as part of the deal.

Officially the alloy head arrived for the 1955 season on both Model 88 and 99 machines. The new model season actually beginning in September 1954. So some official 1954 bikes with alloy heads plus a few before that.

Iron heads are readily available.......frequently appearing on Ebay or other sales sites. I have a spare Model 7 head in excellent condition. It was part of a complete engine which I failed to sell for £100. Posting the head alone to S.A. would cost more than that.

Previously bruce_kirby wrote:

Previously Bruce Mitchell wrote:

Previously bruce_kirby wrote:

Not sure if this has been raised in the past, so apologies if it has in advance.

I note that under the "Models" tab, the dialogue w.r.t. the Domi 88 indicates that from 1954 on the 88 had a welded on sub-frame. IMHO '54 Model 88's still had the bolt-on sub-frame.

Well mine does anyway.......

Bruce

On a similar note I have a '53 88 engine in a box of parts along with an alloy head which I understand from that same write-up didn't appear on the 88 until '55. Is there any way to tell what model a head came from?

Bruce too.

Hi "other" Bruce!

There is a thread on this site covering the heads in quite some detail, starting at the early cast iron head. This should be able to help you as it has excellent descriptions accompanying good photographs, along with casting numbers etc. It will be under this heavyweight message board. But the alloy head appeared in '55. Are cast iron heads available in your bailiwick? I'm down at the tip of deepest, darkest Africa where Norton spares aren't exactly bountiful!

Thanks Bruce, I'll see if I can't find that thread. Not much is available for these bikes in my neck 'o the woods, I'm in Canada and we had 51cm of snow the other day, a record. Thankfully the shop is insulated and heated so play space all year round!

My bike is a 1955 Model 88.Up to September 1954 (ie the start of the 1955 model year) the spec was iron head, pre-Monobloc 276 carburettor, bolt-on subframe, short one-piece rear mudguard and open rear registration plate mount. The battery sat exposed beside the oil tank on the right side. Hubs were iron half-sidth items, 8" at the front.For the 1955 model year, the cylinder head was alloy as standard, Monobloc carburettor, welded subframe, wider rear mudguard with a hinged tail-piece and an enclosed registration plate mount. Hubs are 'full width' items. The front one has the same brake plate as before, an iron drum bolted to an alloy carrier so that it looks like a full width casting. The rear uses the same drum/sprocket and brake plate as the iron spool hub, but with a large alloy spoke carrier. These hubs were used only to 1957 when a much superior full width hub for the front, and a similar rear hub but with the drive studs further out.There were many changes in the 1956 and '57 model years, so it's easy to spot which year a bike is, if it's standard and you know the differencesI personally like the look of the early featherbed machines, and prefer the short mudguard of the pre-'55 bolt-upbikes. Fwiw the Internationals kept the short rear mudguard to the end in '58

The early (Mk 1) head is extremely rare, I was told a figure around 120 bikes supplied with this. The inlet tract is dead straight from carburettor to the bend at the inlet valve. It was deep bored and totally even. I had heard that this head flowed MUCH better than the Mk 2 with bolt-on inlet manifold, due to its double bend .

I once knew a man who had a prototype Model 7. When I first knew the bike, it had the original Mk1 head. The owner of a local motorcycle shop wanted this head so much that he swapped a good '50s alloy head for it. He regarded this swap as a major score.

Before this report, I had not heard of alloy Domi heads being available before 1954. The Model 88 was a scarce beast in the early '50s (Reynolds made the frames, and for a while, were limited to 20 per week - and this bankrupted Norton) and it sounds plausible that Norton had some special bits for favoured customers.

Previously Bruce Mitchell wrote:

Thanks Bruce, I'll see if I can't find that thread

Here http://atlanticgreen.com/nhth.htm are descriptions of all of the Heavy Twins Cylinderheads.

Fritz

Model 7 bikes with the Mk 1 head are much rarer than suggested. There were only 4 built and sold during November 1948 with 2 more assembled and sold shortly afterwards. The records indicating engine numbers from 19617 to 19620 plus 21600 & 22250. The remainder of the batch being stored until April 1949. These were probably given the Mk 2 head with separate mainfold before being released to the public ......... 22545 to 22550. Nearly all exported. General production appears to have got going again by May 1949, starting from number 22830. Again all exported.

There only appears to be around 12 bikes completed with the Mk 1 head and very few actually delivered still wearing it. There are rumours of one complete Mk 1 Model 77 in a private collection in the USA and the remains of a Mk 1 engine in Australia.

There may still be some, equally as rare.iron heads about with the single piece rocker plate & spindle that the Mk 1 heads had as standard and were also fitted to some of the first Mk 2 heads. See attached diagram which is actually an early Mk 2 head. Not Mk 1 as labelled.

Apart from over-heating issues, the Mk 1 head was difficult to cast and then machine internally, in order to achieve a reasonable finish to the inlet tracts. A problem that suppliers of 2 into1 SS manifolds appear to be having nowadays.

T2140 was the first of the iron heads with the separate inlet mainfold. Followed very shortly by T2212 which has better finning to improve through and over the head cooling.

Attachment is the article Dave Comeau and I cobbled together from all the known data at the time (2012).

I never discovered a casting number for the first head. I always assumed that it was 2140. It may well have been.