Can you date this engine?

This is fitted to a Norton frame, ie Triton, I know the frame is 1960, but what is the engine likely to be and what ancillaries should it be fitted with? I think the carbs are wrong.

It is T120R, alternator chain cases, magneto ignition and twin LH monoblocs along with 9 stud head and 750 barrels

I’m really out of my depth with the 650 preunit motors and want to do what’s right for it when I rebuild it. All assistance welcomed.

Should be an early '61: https://www.lowbrowcustoms.com/blog...riumph-motorcycle-engine-frame-serial-numbers

Superb. Thanks very much that’s just what I needed to know. 60 frame 61 engine. It’s almost like they were meant to be together. Better than sticking a unit motor inside it

Flatspot said:

This is fitted to a Norton frame, ie Triton, I know the frame is 1960, but what is the engine likely to be and what ancillaries should it be fitted with? I think the carbs are wrong.

It is T120R, alternator chain cases, magneto ignition and twin LH monoblocs along with 9 stud head and 750 barrels

I’m really out of my depth with the 650 preunit motors and want to do what’s right for it when I rebuild it. All assistance welcomed. View attachment 113272View attachment 113273

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At first, I was thinking that the engine numbering was faked but now I'm thinking that's a rare engine. I would have sworn that there were no pre-unit T120Rs, but I found a couple of references to some being built in 1961.

Parts Catalog 1 (starts from DU101) lists T120, no T120R. Parts Catalog 16 (started from D101, published Sept 1960 so a 1961 manual) does not mention T120R but does show a picture of a T120 Bonneville.

Thanks, I thought I’d read somewhere that the R was added to the T120 bit for the American market(for Racer perhaps?) . My pal also has a T120R Triton, but that one is a unit motor, and somehow the unit motor doesn’t quite look ‘correct’ in the featherbed frame.

Flatspot said:

Thanks, I thought I’d read somewhere that the R was added to the T120 bit for the American market(for Racer perhaps?) . My pal also has a T120R Triton, but that one is a unit motor, and somehow the unit motor doesn’t quite look ‘correct’ in the featherbed frame.

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A unit triumph engine has no place in a featherbed frame

'R' means Road and 'C' is Competition according to JR Nelson.

That's the first T120R pre-unit engine that I have ever seen on literally dozens of Britbike/Triumph forums and fecebook groups, over more than 30 years of owning nearly 50 of them, and rebuilding or restoring another 2 dozen plus...

I wish people could get over the fact that Tritons are just fine for their owners, as are unit Triumph engines in Featherbeds. The claimed "improper" weight distribution is baloney, as is the "too much empty space" argument.

L.A.B. said:

'R' means Road and 'C' is Competition according to JR Nelson.

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Interesting - have lots of books but not that one and I don't try to be an expert. Also have/have had T120C, T120R, TR6C, TR6R, T100, T100C, T100R, all unit construction, but none unmolested so it's hard to say how they left the factory.

Several sources say the T120R was the US T120 and T120C was the high-pipe competition (off-road). It all gets confusing when you add TR6C (road completion?) and TR6R (road). My TR6C definitely came with E.T. Ignition and high pipes as did my 66 500 (bike stolen in 1970, don't remember the model identifier)

The first parts manual I have that lists the T120R was published in 9/68 and is part SPC.7 which is the US version of SPC.9 which is the UK and General Export. As far as I can tell, there was none just called Catalog 7. Catalog 6 does not differentiate in intended destination, and Catalog 8 is like Catalog 6 in that they only list TR6 and T120.

Also, they were inconsistent between the 500s a 650s. T100C (US low pipes, 67 on, I think)/T100R (US Low pipes 67 on, I think), and several other suffixes earlier on.

grandpaul said:

That's the first T120R pre-unit engine that I have ever seen on literally dozens of Britbike/Triumph forums and fecebook groups, over more than 30 years of owning nearly 50 of them, and rebuilding or restoring another 2 dozen plus...

I wish people could get over the fact that Tritons are just fine for their owners, as are unit Triumph engines in Featherbeds. The claimed "improper" weight distribution is baloney, as is the "too much empty space" argument.

View attachment 113280

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I have to respectfully disagree and this photo further proves my point
Of course anyone can build whatever type of Triton they like
(As long as it's a pre unit )

baz said:

I have to respectfully disagree and this photo further proves my point
Of course anyone can build whatever type of Triton they like
(As long as it's a pre unit )

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His original point was the same as mine. A T120R is a rare pre-unit engine. The point has nothing to do with Triton per se.

marshg246 said:

His original point was the same as mine. A T120R is a rare pre-unit engine. The point has nothing to do with Triton per se.

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Yes I understand the original point
But that's not the point I answered

My eyes weren’t open, I see there’s a Triton forum in which I’ll put more about this one.

For the Untidy States , and New Zealand , They were RRRR's . T 120 R . Mate .

T120R
D11600 odd is late 61 . maybeeven Oct .

WHEREAS 50s T 100 R , RR , & RS were RACE , Like ' C ' ( comp . )s . but better . !Fair Dinkum .
650 ' C ' was OFF ROAD , Comp . AND there were 1960 TR7 off road BONNEVILLES .
Bonneville TR7 . Pre Unit

There were TR6 SC & SS also . east & west coast could & did vary spec. & designation . U.K. spec. usually more staid .

The Date will be cast in a circle in the timing cover houseing . ( and in the Rocker / valve housing on the head )
Date of CASTING so stamped maybe a few months later .

Theres a film of T 100s being built , in the 50s . They still ruled the world in the 60';s .



original goes trough to the dyno & shipping .

Following on from this, now knowing my T120R motor is a ‘61 I can see that the spare set of TR6 cases are 1960.

Is there a way to determine what year a slick shift gearbox was built? Number on mine is 104297. Externally it isn’t too bad, but I intend to open it up and if nothing else I’ll fit a full set of springs and perhaps do a ‘slickshift’ delete.

I can now answer my own question. The box is 1959.

I’m glad I opened it up to fit new springs, as I also needed to fit a new lay shaft bush as the old one was broken, naturally as well as springs I also renewed the bearings.

And…………. It also had 3 gears with at least one tooth missing, with the remnants inside the box as well as a random nut (how?)

I looked up the gears part numbers and managed to get some really good s/h ones off eBay. Reassembled and it’s put away until time to use it.

Of course, once I’d done all of that I looked through the boxes of “other bits” that came with the bike and found 3/4 of a 1960 gearbox that had all 3 gears in good condition. I could have used them!

I also found a very good set of TR6 crankcases, and a reasonable spare crank (although that has gone away to be properly assessed to see if it’s any good.

And the cherry on top of the cake is a pair of mk11 Morgo barrels and 0.00 pistons in nearly new condition.

That’s a heck of a spares cache you got there

Wotyer wanna DO , is LOOK AT the Index Plunger / SPRING . Very Carefully .

Thats wot holds it IN GEAR .

or thats the theory anyway . If you give it a good tug , and it stretches to six inches . Ooops , squash it back a bit - Itll stay in gear much better , but the change'll be a bit stiff , for a while .


Ahem . Have a GOOD GLARE at those bits . Carefully .

Id strip It and keep matched / mating components. LIKE . And see the bottom mounting hole is UNWORN . Not Oval . Perhaps REAM to fit 10 m.m. stud . IF a 10 m.m. drill bit end will start , in the hole.
the blunt end . The hole ends are bigger than 3/8 . So look atit CLOSELY . dither , prvaricate , and SECURE SECURELT as its wot hold it ALL in ALIGNMENT . And ' We All ' use dual top adjuster , one each side .

To LOCK IT STRAIGHT . Adj. Korekt . Tighten Crossbolt . THEN wind Adj up firm to see it wont shift back and pull the primary . Or it will ! .

You use a straight edge and feeler to double check chain / sprocket alignment . Carefully . Use Notepaper . Keep a RECORD . Of THINGS .

Like shims , amount lapped off .
AND
LAP THE TAPERS , with paste , on the mainshaft .