Dominator 88

dynodave said:

What is to just learn? We've been saying it over and over the crankcase castings are the same for all 61+ late domi and commando through 20M3 which we now know as fastbacks as late as early 70 . just drill/tap the cases for small bolt pattern barrels makes them for 650 or 122(88)....The barrels HAD TO BE 650 as they were small head bolt pattern and atlas were desaxe medium head bolt pattern.

The 650 is not a desaxe engine...sleeve it and offset rebore......not likely. Possibly if it was bored small and correctly repositioned. Ever heard of a small bore large bolt pattern OEM barrel????
What am I missing? It's not complicated
Only thing that may have changes is the cam end breather changed to atlas style instead of rear case exit???? who knows . anyone seen a mercury?
Repositioning the case head drain down hole is a minor issue?

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Re drilling the bottom crankcase studs on a 500 domi crankcase to take a 750 pitch holes barrel is not a minor issue, you might get away with it the opposite way round, but then you will have a crankcase breather as per 750 that the 500 doesn't have.
Also, very few 500 with alternators were made compared with the 750.

From memory about 600 Mercuries were built , not many would have been sent to the States,not really their thing. Still all facts are of interest and good for discussion . Unless we get into politics !!. The Mercury was John Hudsons ( late NOC president and factory service engineer) favorite bike . He rode his till the end.

annajeannette said:

well it may look something like but in fact the dimensions of the bigger engines are not the same as the model 88 as these engine are that bit smaller

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AJ linguistic skill seem abbreviated as well as her understanding of the machinery

I reply:

dynodave said:

4 different cases:
1 very early M7,
2 later M7/88/99 dynamo,
3 early alternator 88/99,
4 then last from the rear bulge cases starting with the 1960 650/88/99 atlas ( and a few earlier ones) the timing case CASTING # did not change until the single chain/20M3S commando starting in 1969 with the "S"
Strange? The castings are the same # arent they? So the only difference would be small barrel bolt pattern 500/600/650 or large barrel bolt pattern for 750's

Case the same size ....only the barrels are different

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Only version #4 is interchangeable for small barrel engine when finish machined as such.
Version 4 bulge castings: Drive 20976/timing 20666 are suitable for finish machining to small barrel specs and also suitable for finish machining to large barrel 750 specs.

norton bob said:

Just learnt that the last 650 motors built used modified Commando cases , what did they do about barrels I wonder.

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Implies raw castings were finish machined to final large barrel commando configuration ... then modified and used to build 650.
Please tell us your authoritative source of this information. I have no information source that implies this or can prove it,

Bernhard said:

I think you will not just find the cases are not the same , but also as the engines were bored/ stroked the holes on a 750 barrel will no way match a 500 and vice versa.

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Both of us then agree the large barrel and small barrel engine cases are not inter changeable.
However the original raw castings are identical
"The castings are the same # aren't they?"

My original and continuing assertion is the RAW drive 20976/timing 20666 CASTINGS were finish machined in 2 configurations. small or large
I further assert, without proof , that the 750 atlas and later 750 commando, these same raw casting/cases should also be sufficiently strong for any 88(122) engine when finish machined for small barreled engines.
The parts book shows from 61-on the small barrel cases were bulge cases as used on 1.75 cranks. For me factory documentation is adequate proof for now.

Rumor that the old parts bin supplies early cases for 122 engines for some short or extended period until 1966, I would need a fair amount of on the ground documented field research of 122 engines before I would accept the rumor as fact.

t ingermanson said:

My Mercury motor has no cam end breather as an Atlas would.

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I can only wonder what is the process and final product cofiguration of the atlas cases, which is a final product configuration, being modified for a mercury?

Oh well....

dynodave, the above is excellent description of the Norton crankcases, but something has just struck me, it is that two different people might be discussing crankcases that are blank and unmachined and trying to compare them with crankcase that has already been machined, if you see what I mean.

The info on Mercury parts came from an very respected senior NOC member with access to factory records .Interestingly the Mercury also had Commando head castings too ,modified to 650 specs along with Commando box with a featherbed Mainshaft. I will ask him about the bulge cases history on the 88/99 bikes . A lot of the factory records are very poor quality and difficult to read even on the orriginals. Engine numbers indicate that production numbers were nearer to 750 . They do come up for sale regularly in the uk. One for sale currently. Wish I had space .

When the need arises, I email with Phil Hannam... info goes both ways! Even met with Roy Bacon once on Isle of Wight for a long talk during one of the vintage bike club meetings.

The 06-0380 raw casting head, finish machined as a small bolt pattern NHT head, has been on my website for at least 10 years. It is a no-spigot version.
How were the heads "modified"?? or were they in fact manufactured TO 650 post 1966 spec? It is probably Norton PN 25358

Not understanding your choice of words.. "commando gearbox" yes similar but different
1. mainshaft for coil spring clutch but also need ...
2. featherbed outer cover for cable entry angle ...
3. clutch release lever
4. There are quite a few AMC main housing castings. For the most part 4 different case versions out of about 25 gearboxes I own will fully interchange.
disregarding the 1 L shape ones Matchless?
Or the spacer at the top for the commando

norton bob said:

Engine numbers indicate that production numbers were nearer to 750 .

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750 what ?
number of Mercury units manufactured ?
Yes there are a few here in USA/Canada, but not many.
I've believe that bike model quantity was audited by counting units in the records rather than the lowest # subtracted from the highest#. The bike models were intermixed in the VIN register weren't they? But the bike vin register was sequential. (at least that is what I have seen) Maybe they kept a seperate log...I was not there then.

dynodave said:

Rumor that the old parts bin supplies early cases for 122 engines for some short or extended period until 1966, I would need a fair amount of on the ground documented field research of 122 engines before I would accept the rumor as fact.

Click to expand...

norton bob said:

According to Roy Bacon the bulge cases came into use on the smaller dommies from 64 , Don't know his source for that ,but if true it explains the scarcity .

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In the USA or maybe worldwide , a survey of 122 engine by VIN and factory batch# for the bulge/no bulge issue will possibly only be done by phone or internet. Bulge case part number is 23263. The prior 88/99 alternator no-bulge case 1959 PN is ? (I don't have this IPL
Call everyone you know with an alternator 122 engine ....data: serial number and bulge or no-bulge
cheers
122/81415=no bulge

Hi Dave, If it works that would nail it. Phil says that the build doc's that he has show that the Dommy bikes from 1960 on paper should have had the bulge cases. However having known some of the guys that worked in the Industry ,they were not beyond ignoring the management. If I was running a production line and had the choice of finishing bikes with a stack of perfect cases or waiting for some bulge cases that were not actually needed,-------.Then production was switched to Woolwich where they could not turn out a usable case without filling a skip with rejects. Every good bulge case was needed for the 650 and export. I think the truth is somewhere between .

dynodave said:

Call everyone you know with an alternator 122 engine ....data: serial number and bulge or no-bulge

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norton bob said:

Hi Dave, If it works that would nail it. Phil says that the build doc's that he has show that the Dommy bikes from 1960 on paper should have had the bulge cases.

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Data gladly accepted here or PM
Would anyone please disclose the PN for the pre bulge cases AKA my 59 engine. thanks

dynodave said:

What is to just learn? We've been saying it over and over the crankcase castings are the same for all 61+ late domi and commando through 20M3 which we now know as fastbacks as late as early 70 . just drill/tap the cases for small bolt pattern barrels makes them for 650 or 122(88)....The barrels HAD TO BE 650 as they were small head bolt pattern and atlas were desaxe medium head bolt pattern.

The 650 is not a desaxe engine...sleeve it and offset rebore......not likely. Possibly if it was bored small and correctly repositioned. Ever heard of a small bore large bolt pattern OEM barrel????
What am I missing? It's not complicated
Only thing that may have changes is the cam end breather changed to atlas style instead of rear case exit???? who knows . anyone seen a mercury?
Repositioning the case head drain down hole is a minor issue?

Click to expand...

well the 650s were desaxed by one eight to the rear of the barrel the 750 was 3/16th to the rear of the barrel which is more noticeable and the first crankcase that had the bulge at the back where the Norton Manxman 650 built from 1st of november and by late march the model 88 and 88ss and model 99 ss had received the same crankcases by then and long with the high lift camshaft and valve train but the model 99 remained with a standard cylinder head until later on end of july 1961 were the 99ss then got the 650 ss heads

dynodave said:

Data gladly accepted here or PM
Would anyone please disclose the PN for the pre bulge cases AKA my 59 engine. thanks

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Per the “Spare Parts List for 1959 Models...” the 88/99 driving side is 21010; timing side is 21009; crankcase with timing cover is 21013.

Scott

kernel65 said:

Per the “Spare Parts List for 1959 Models...” the 88/99 driving side is 21010; timing side is 21009; crankcase with timing cover is 21013.

Scott

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Awsome Much thanks....part # is good and helps info organization. My 59 bottom end is fresh assembled and not likely to come apart for a "casting" # check . LOL

annajeannette said:

well the 650s were desaxed by one eight to the rear of the barrel the 750 was 3/16th to the rear of the barrel which is more noticeable

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I understand what you say may be possible . I have 88, 99 and 650 barrels and lots of measuring equipment . I am not going to judge without proving for myself you are right or wrong.
Since 99/650 height barrels are taller than 88 barrels I would not expect them to be in the same position unless you change the angle of the push rods etc....
However this is not the focus of the investigation. If the cases and head are identical , certainly norton engineers could derive the correct positioning for short 88 barrels?
If 88 is the reference engine being first... then of course the 99/650 head would be pushed toward the rear.

annajeannette said:

by late march the model 88 and 88ss and model 99 ss had received the same crankcases

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This very statement is the point of controversy and rumor, This is the very focus of the inventory survey. 1960 thru 1966 88SS only serial # and bulge or no-bulge
Data gladly accepted here or email or PM.

dynodave said:

I understand what you say may be possible . I have 88, 99 and 650 barrels and lots of measuring equipment . I am not going to judge without proving for myself you are right or wrong.
Since 99/650 height barrels are taller than 88 barrels I would not expect them to be in the same position unless you change the angle of the push rods etc....
However this is not the focus of the investigation. If the cases and head are identical , certainly norton engineers could derive the correct positioning for short 88 barrels?
If 88 is the reference engine being first... then of course the 99/650 head would be pushed toward the rear.


This very statement is the point of controversy and rumor, This is the very focus of the inventory survey. 1960 thru 1966 88SS only serial # and bulge or no-bulge
Data gladly accepted here or email or PM.

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Here's a pair of 88 alternator jugs underneath a pair of 650ss jugs, bottom to bottom. Bolt through the forward central mounting stud hole to insure registration.


Second pic looks down the bores, to display concentricity of the 650ss bore to the 88 bore.



I would suggest there is no front/rear offset difference to the 88 vs 99 vs 650ss vs Mercury cylinder bores.

VERY NICE!!!
standard engine is the bore being centered above the crank.
co-locating on any or all of the front 3 studs is the key.
If an 88 was a nondesaxe then the 650 is nondesaxe.
I have the lifter tilt back angle some where?
Makes me wonder if the average 650 pushrod angle is a bit more upright (minor)?
Would seem unlikely they change the angle of the lifters on the cam.

I will eventually be mounting an engine case on the milling machine, with the Heidenhain DRO, and precision measure the bore hole location of 122-16-18 and 20 barrels.
Desaxe will not hide from me...LOL

My Mercury is an SS.

Glen

worntorn said:

My Mercury is an SS.

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mercury was single carb? single carb SS?

It took a while for me to remember but the 20666 is a mold # and is only a partial part of the case making process. So obviouslly the outer casting mold determines that portion creating the bulge for the 650 or 750 final casting.

My bike was ordered and built in 1969. By then Norton had replaced the 650SS model with the single carb Mercury.
Harry Firth at Firth Motors in Ontario felt he could sell the Dove Grey/Black/Chrome twin carb SS models but wasn't keen on the single carb plain Jane blue Mercury.
So he ordered 5 " Mercuries" but asked that they be built as 650 SS models. On the official Norton register these bikes show up as Mercuries, however they are identical in spec to the last run of 650ss bikes.

Glen