750/1973 parts

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Hi All.
My 1973 230... (one of the last 750) Roadster has a RH6 head with 932/29/30 carbs.
The crankcases (that match) are not those of 1972 (or the first 1973) with the breather on the rear of the left driving case and with the smal magnetic drain plug, but has the same cases of the first 1973 850 with the breather on the timing side (where was the blanking plate) and has the large oil drain plug as 1968/71 type.
The seat has the basketweave cover.
Veglia instruments with longer black bodies.
Is this the original stuffs?
Thanks.
Ciao
Piero
 
If it has 32mm carbs, it may be a Combat engine. Is the cylinder barrel all base nutted or are the side bolts through bolts ala 850?
 
Danno said:
If it has 32mm carbs, it may be a Combat engine. Is the cylinder barrel all base nutted or are the side bolts through bolts ala 850?

As it has a 230xxx serial number and an RH6 head then it's unlikely to have been a Combat.
The post-Combat era 750 Commandos that had either an RH5 or RH6 head had 32mm carbs as standard.
 
L.A.B. said:
Danno said:
If it has 32mm carbs, it may be a Combat engine. Is the cylinder barrel all base nutted or are the side bolts through bolts ala 850?

As it has a 230xxx serial number and an RH6 head then it's unlikely to have been a Combat.
The post-Combat era 750 Commandos that had either an RH5 or RH6 head had 32mm carbs as standard.

Hi Les,
Yes, i agree.
About the crankcases may be the last 1973 can already had the first 850?
Of course the barrells have all base nutted.
Ciao
Piero
 
pierodn said:
About the crankcases may be the last 1973 can already had the first 850?

I could not say for sure, it seems unlikely but perhaps not entirely impossible.
Even if the factory had produced a relatively small batch of a couple of hundred or so 750 models with '850' crankcases then we should at least have seen a few more examples of 230xxx models with '850' style cases reported on the forum (or elsewhere) by now, so perhaps other 230xxx series owners can say which type of crankcases they have?
 
My 230615 has the crankcases with the rear mount tower breather and only the small drain plug with magnet.
No big sump plug.
32mm Amals and plain compression cylinder head.

It was a black Interstate, with the non-balanced low cigar silencers with removable baffle.
 
Bob Z. said:
My 230615 has the crankcases with the rear mount tower breather and only the small drain plug with magnet.
No big sump plug.
32mm Amals and plain compression cylinder head.

It was a black Interstate, with the non-balanced low cigar silencers with removable baffle.

Hi.
I mean.
But the 1973 last 750 should have the RH6 head (low compression), or not?.
Ciao
Piero
 
L.A.B. said:
pierodn said:
But the 1973 last 750 should have the RH6 head (low compression), or not?.

The RH5 was the "low" (standard) compression head.
The RH6 was the "high" compression head but was not as high compression as the Combat head.

http://www.nortonownersclub.org/support ... tification

Hi Les,
I mean.
The one previous owner of my bike sais that engine is what she had bought, never changed.
In any case, some say that the breather of this type like 850 should work better than 1972 one.
Thank you.
Ciao
Piero
 
pierodn said:
The one previous owner of my bike sais that engine is what she had bought, never changed.

Is the serial number anywhere near Bob Z.'s (230615) or is it significantly different (much earlier or later)?
 
Bob Z. said:
My 230615 has the crankcases with the rear mount tower breather and only the small drain plug with magnet.
No big sump plug.
32mm Amals and plain compression cylinder head.

It was a black Interstate, with the non-balanced low cigar silencers with removable baffle.

I was not aware there were any non-Combat 750s equipped with 32mm Concentrics from the factory.
 
L.A.B. said:
pierodn said:
The one previous owner of my bike sais that engine is what she had bought, never changed.

Is the serial number anywhere near Bob Z.'s (230615) or is it significantly different (much earlier or later)?

Hi Les.
The numbers are later 2309xx, about the last.
About the new 850 breather type, is troo that works better than 1972 one?
Ciao
Piero
 
About the new 850 breather type, is troo that works better than 1972 one?

Depends, the 72 is directly into the crankcase so closer to the source of the air movement eg the pistons, but it work best with the return oil pick up moved to the rear or it gets swamped with oil. The 850 is away from the source and air movement is limited by the holes from the crankcase to the timing chest but is not swamped with oil. You have what you have and best to run with it, if you have the 72 cases with no large sump nut then change the pickup to the rear and fit a XS reed valve inline. If you have the 850 then look at the mods to lower the oil level in the timing chest, increase the airflow from the crankcase and also fit the XS reed valve.
 
Danno said:
Bob Z. said:
My 230615 has the crankcases with the rear mount tower breather and only the small drain plug with magnet.
No big sump plug.
32mm Amals and plain compression cylinder head.

It was a black Interstate, with the non-balanced low cigar silencers with removable baffle.

I was not aware there were any non-Combat 750s equipped with 32mm Concentrics from the factory.

The post-Combat 750 models still had 32mm carbs although there was a 30mm RH1 head and carb option (mainly used on the '73 Hi-Rider).

http://www.classicbike.biz/Norton/Parts ... _73-74.pdf

Cylinder heads pdf p.10
Carbs pdf p.28
 
For what its worth, my 73 came to Australia ex-Canada. Was originally a Black Roadster, 32mm carbs, I assume RH5 head but no actual marking stamped anywhere on it, breather behind LH case, long black gauge holders, late square tail light, ANG fork trees (IE 850 type), basket weave seat.
Matching engine, gearbox and frame VIN 230034. date stamped on frame ID plate DEC 1972

I have recently sent a copy of my Norton VIN information list (with over 2000 VIN from 1952 to the last Commando built) that I have been compiling for many years to Jerry on this forum. He plans to publish it in a new website and give me access to update it. I am sure this list will be very interesting to forum members as it has many examples of the 230 series machines built December 1972, as well as the 235 series built Jan to March 1973 with 750 STD, 850 STD machines and 750 Shortstroke engines all built stamped with a 235 VIN.

I have also saved folders of photos of the majority of entries on my list for reference and in time will complete the large task of properly putting them into chronological VIN order.

In time I will save it all to an external hard drive and mail it over to Jerry for inclusion in his planned website for that kind of information.

Seeing 230935 is supposed to be the last 230 series machine, your bike is close to the end Piero. Is there a build date stamped on the frame ID plate? That would be very interesting to know please.

It is interesting that the 230 series seem to have been all built (to the best of my knowledge based on the many build date examples in my list) during December 1972 but Roy Bacon gives a date of October 1973 for 230935.

I think he must have had access to the dispatch records and not the production records for a lot of his information. I think that some 73 750cc machines for whatever reason were held over for a time before dispatch (perhaps as the 850 was in now in production and demand).

As already stated above, the 230 series built in Dec 72 were not the last 750's built considering the build dates Jan-March stamped on the 235 machines.

Perhaps 230935 may for whatever reason been held over at Andover and became the last 750 DISPATCHED in October 73 rather then being the last 750 BUILT???

As has been stated by Joe Siefert the records (both production and dispatch?) for late 750's have been lost. Perhaps they were among the various documents thrown out when Andover closed?

I received a letter from John Hudson many years ago and he told me that a lot of documents were thrown onto a garbage pile to be dumped when Andover closed but an employee saw this and collected it and delivered it onto the front steps of a boarding house John was staying at and he says he got a big surprise when he came home and found the boxes waiting for him. John did not state exactly what he was given but I know there were sales brochures and I think period factory photographs of which he sent me a few. All that he got he later passed on to the NOC.

I will copy his letter and post it here some time when I can get the time to find it amongst all my bike related stuff.

Regards, Tom
 
Snortn750 said:
It is interesting that the 230 series seem to have been all built (to the best of my knowledge based on the many build date examples in my list) during December 1972 but Roy Bacon gives a date of October 1973 for 230935.

Norton Service Release No. N3/39, March '73, regarding the stronger replacement centre stand kit, refers to 230536 to 230685 (and 221545 to 221644) as already having the stronger '850' centre stand so production seems to have reached at least 230685 by that date.
 
Hi Tom.
I have two 1973 750.
One is 23009x, and have the rear driving side breather like 1972; NOC says this bike was of december 1972.
The other 2309xx do not have any date on the neck, and i have never dedmount the left Zplate where is stamped sometime (1971 i have seen) the date.
Thank you.
Ciao
Piero
 
kommando said:
About the new 850 breather type, is troo that works better than 1972 one?
If you have the 850 then look at the mods to lower the oil level in the timing chest, increase the airflow from the crankcase and also fit the XS reed valve.


Hiband thank you.
It means i must drill a hole under the oil pump?
What must i do to incressethe airflow from crankcase?
Where i must fit the XS reef valve? On the blanking plate where there is the tube or on line after the tube?
Thank you.
Ciao
Piero
 
It means i must drill a hole under the oil pump?

Its detailed on the forum, not sure exactly where the hole is but not far from the oil pump.

What must i do to increase the airflow from crankcase?

Extra holes but the oil level mod increases the holes so gives you the increased airflow anyway so no need to add to these

Where i must fit the XS reef valve? On the blanking plate where there is the tube or on line after the tube?

Depends on the XS valve, there are different types and the connections vary so you need to get the valve and then see the best way to mount them. I stick EGR valve into ebay as a search on motorcycle parts (that is the type of valve it is) and pick ones that fit into the rubber line.

eg http://www.ebay.co.uk/itm/YAMAHA-CYGNUS ... SwhRxXK2MP


750/1973 parts



and also in black

750/1973 parts
 
pierodn said:
L.A.B. said:
pierodn said:
But the 1973 last 750 should have the RH6 head (low compression), or not?.

The RH5 was the "low" (standard) compression head.
The RH6 was the "high" compression head but was not as high compression as the Combat head.

http://www.nortonownersclub.org/support ... tification

Hi Les,
I mean.
The one previous owner of my bike sais that engine is what she had bought, never changed.
In any case, some say that the breather of this type like 850 should work better than 1972 one.
Thank you.
Ciao
Piero

Does your machine have 850 type cylinders or 750 type? Thinking maybe a short stroke 750. That would have the 850 crankcase.
 
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