What do I have here?

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Nigeldtr

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Jul 26, 2012
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Hello,

I have just had delivery of a rolling project for complete rebuild. It should be a 1970 750 Roadster but it has a skimmed head with "C" marking, hi compression pistons (I think) and a yet to install 560 ss cam. It was slung together by the seller to make it look more than it is! Anyway can anyone help me identify what I should be rebuilding here?

PS looks much better in the pics than it is!

Thanks

Nigel

What do I have here?


What do I have here?
 
ID plate number/engine number would help identify it. It's got the 69/70 halo headlamp, but the seat is for a later year. Breather off the drive side? Central oil tank?

Dave
 
Hello Dave,

Engine and frame numbers match - 20M3S 136*** central oil tank and breather off the camshaft (drive side)

Nigel
 
Whatever you do, make sure the side cover logos are parallel to the top of the z plates. Engine and pipes sure look clean.
Good luck!
 
136xxx should put it after the last S, but still an early model before 71. Yes the side panel decals should be parallel to the ground, not the top of the panel.
 
Nigeldtr said:
Hello,

I have just had delivery of a rolling project for complete rebuild. It should be a 1970 750 Roadster but it has a skimmed head with "C" marking, hi compression pistons (I think) and a yet to install 560 ss cam. It was slung together by the seller to make it look more than it is! Anyway can anyone help me identify what I should be rebuilding here?

PS looks much better in the pics than it is!

Thanks

Nigel

Welcome to the site Nigel.

The "C"mark on the head plus the fact it is skimmed would indicate it came from the Combat model of 1972.
Skimming the head is how they raised compression for the Combat so unless you can verify it directly I suspect your pistons are standards, since the combination of Combat skimmed head plus high compression pistons would seem to produce a CR probably too high for todays highest octane availabe car gas.
If they have put the high compression head on it may also mean they installed the high peformance SS Combat cam so verifying its lift to see if that is the case would be useful. Combats are really good as hot rods but for regular spirited riding usually a bit of an overkill. 21 tooth primary sprocket best, 19 tooth on Combat makes for pretty buzzy riding that for regular riding too much.
If Combat head and Cam then you may want to verify that the main bearings are superblends, however I'd guess that since the bike probably has quite a few miles on it by now they have already been installed.
You will probably want to research the whole Combat story.
Click to expand...
 
A Robinsons 58 . :P ( 58 cross bred ) :D . This leaves you free to expess your individuality . 8)

indeed , IF you fit sidecover scrawl , put a wire of stick along the top of the alloy plate , and get a volenteer to hold another above that .
use a ruler to check the gaps even / parrallel , then put a chalk line along sidecover . thats your ' horizontal datum . Now we know . :lol: :wink:

Presumeably its 32 mm carbs . Needs nice valve springs and clearances set , with a SS cam . Nothing but the Best . :D

Might pay to set up the front brake to its optimum . Check drums round , fit some fancy lineings - AM 4 or whatever .
Even a Disc can leave you with that ' am I gonna stop / get around it ' thrill of waiting to see , on a snortin Norton .

If a Dual Disc front hub comes your way , it could be just the thing for the autobahn , 23 T only gives you 130 mph @ 7.000

p.s. nice colour , dont change it .

p.s.s. AND its got the early , square oil tank . !

p.s.s.s. :oops: armour all , on that seat cover , if its not ripped , a few ( dozen ) coats , will have it like new . Or Better .
 
Hi Nigel,
your bike is beautiful as well.
Is a wonderful 1970 's roadster like this in photos that sell in Italy for 12.00,00 euros.
Do not change the front end, is beautiful so even if the disc brakes better.
If you decide to change the front end we can commute to equal, I have a complete set of forks with slider disc, wheel with disc, caliper, etc.
But don't do it!.
Piero
What do I have here?

http://m.moto.it/mercato/epoca/annuncio/4885453
 
You've got a good basis to start from there for either an early Roadster as it stands, or 'S' Type with the super sexy high-level pipes
The later, steel tank is a good thing - the original glassfibre tanks are not friends with modern fuels.
Personally, I'd want to change the seat, but otherwise it's got the 'right stuff' to be a classy bike.

I can't agree with Matt though - it's crying out for a metalflake paintjob!

What do I have here?


What do I have here?


What do I have here?
 
B+Bogus said:
You've got a good basis to start from there for either an early Roadster as it stands, or 'S' Type with the super sexy high-level pipes
Click to expand...

Although it may not exactly matter, serial 20M3S 136*** is probably too late for it to have been an original 'S' Type.
 
pierodn said:
Hi Nigel,
your bike is beautiful as well.
Is a wonderful 1970 's roadster like this in photos that sell in Italy for 12.00,00 euros.
Do not change the front end, is beautiful so even if the disc brakes better.
If you decide to change the front end we can commute to equal, I have a complete set of forks with slider disc, wheel with disc, caliper, etc.
But don't do it!.
Piero


Hi Piero,

I bought it because I love the look of this year with the halo and twin leading shoe front brake. Its going to cost a small fortune but I'll enjoy doing it! Super picture - a real motivation!

Nigel
Click to expand...
 
B+Bogus said:
You've got a good basis to start from there for either an early Roadster as it stands, or 'S' Type with the super sexy high-level pipes
The later, steel tank is a good thing - the original glassfibre tanks are not friends with modern fuels.
Personally, I'd want to change the seat, but otherwise it's got the 'right stuff' to be a classy bike.

I can't agree with Matt though - it's crying out for a metalflake paintjob!

Hi Andy,

Thanks for the motivation, the amount of work ahead is starting to hit me now but the pictures are awesome :-)
Nigel
Click to expand...
 
" Anyway can anyone help me identify what I should be rebuilding here? " ? its a Elastic Band Norton , you can tell by the Muffler Mounts ! :D :P

Looks fine like it is , you just need to see it has a crankshaft , and things like that , in it . :wink:
 
Here are a couple of pictures of the cams that came with the bike. One is new and has 960 ss written on it (wrapped in card from Megacycles), the other is re-profiled and has rather pointed lobes with the same high lift on inlet and exhaust - no markings?

As mentioned, it has a combat head and what seem to be hi compression pistons -picture below. The question is, what do I use for the rebuild. My 850 is a little tame so I could make the 750 a little hotter :-)

Any ideas about the cams and what compression I might have with these pistons?

Nigel

What do I have here?


What do I have here?


What do I have here?
 
Are you sure that's not 560ss? The pointy one is probably stock.

From Megacycle catalog;
"560-SS .390" 276° 104° flat Reproduction of factory “SS” profile. 34 btc/62 abc .006"
.335" 272° 104° Use modified pistons and springs. 60 bbc/32 atc .008"
 
If you're going to hot up a 750 , I would not use that type piston. These were the ones that the top came off on the combats.
 
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