72 Interstate 750

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Cuppy

Cuppy

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Hi All,

I am a Norton newbie and just picked up this 72 yesterday (serial 206709). It is not running presently as it has been sitting in some old man's daylight basement for the last 25 years. I could really use some advice from the experts if anyone is willing to chime in it would be greatly appreciated. My intention is to get it running and plan a full resto as I get the time. I have owned Triumphs so somehat familiar with Brit bikes. (Love them). Bike appears to be completely stock to me. I'm assuming it is an Interstate based on large tank and side cover design (missing RH cover). Bike kicks over and has good compression.

1) Is it ok to flush all fluids, go through the Amals completely and see if it will run?
2) Assuming it's a Combat engine, can I run it prior to modifications? It presently has 5000 miles.

From what I've read in places it's amazing this engine hasn't blown up by now.

P.S.
If anyone has a trick to get a new chain on when there is not one existing.

Chime in if you can and I hope this is the right place for this post. I can't figure out how to add an attachment.

Dave in Maine
 
Last edited:
Cuppy said:
1) Is it ok to flush all fluids, go through the Amals completely and see if it will run?
Click to expand...

Yes, I would say so.


Cuppy said:
Assuming it's a Combat engine, can I run it prior to modifications? It presently has 5000 miles.
Click to expand...

206709 and an apparent Interstate is almost certainly a Combat model and too early to have had the spin-on cartridge filter originally but a worthwhile modification if it hasn't already been fitted.
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

Cuppy said:
From what I've read in places it's amazing this engine hasn't blown up by now.
Click to expand...

Depends on how they were treated to a certain extent.

Cuppy said:
I hope this is the right place for this post.
Click to expand...

Yes.

Cuppy said:
I can't figure out how to add an attachment.
Click to expand...

You need to be a VIP member to upload images etc. directly. Non-VIPs must use a picture-hosting website.
 
I remember talking to my local dealer way back when and he said there was a recall on the Combat Nortons to replace the main bearings. Correct me if I'm wrong about this. So, maybe the mains have been changed to the Super blends?
I would clean the carbs, drain and replace the oils and flush the oil tank. Run it for a bit and replace the oil again. I agree that adding a spin on filter would be a big plus. To replace the chain when there isn't one is a bit of a pain. I would pull the chain guard and then fish the new chain through with a piece of string or wire to drag it over the transmission sprocket. This can be a two-person job and you will spend a lot of time on your knees or back getting it "threaded" over the sprockets.
Hope this helps.
John in Texas
 
Thank you L.A.B. for the responses. I will take your advice on the oil filter. I have signed up for VIP.
72 Interstate 750
 

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The petrol tank is probably fibreglass and if you're going to keep it perhaps you should get it treated first. To get the bike running the remote can and tube will do the trick.
 
The tank is in fact fiberglass. How do I go about getting it treated?
 
Cuppy said:
The tank is in fact fiberglass. How do I go about getting it treated?
Click to expand...

Examples (no personal recommendation):
www.thebonnevilleshop.com

TRIUMPH, NORTON, BSA, HARLEY, INDIAN, CASWELL FUEL AND OIL TANK SEALER PN# TBS-CAS-CLEAR

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Previous discussion:

Gas tank sealer

This is an experiment to see how the gas tank sealer I bought wouls work out. The first thing I did was to coat a coke bottle and let it dry completely. Then I filled it with methanol and let it sit for a week, in the course of the week, I inserted a piece of fiberglass material from a...
www.accessnorton.com www.accessnorton.com
 
Since there is no chain existing, can anyone recommend the number of links I should look for in a new chain? I know I will likely have to cut a few out.
 
Cuppy said:
Since there is no chain existing, can anyone recommend the number of links I should look for in a new chain? I know I will likely have to cut a few out.
Click to expand...
99 links, which implies a half link. Most will be 106 and you have to cut them down to either 98 or 100.
 
Cuppy said:
Since there is no chain existing, can anyone recommend the number of links I should look for in a new chain? I know I will likely have to cut a few out.
Click to expand...

If it has a standard 19T Combat gearbox sprocket then 98 links (01.7376)...
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

...however, the rear drum sprocket teeth look worn in the picture so the gearbox sprocket could be the same or worse, and a new chain isn't going to last long on worn sprockets.
 
L.A.B. said:
If it has a standard 19T Combat gearbox sprocket then 98 links (01.7376)...
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

...however, the rear drum sprocket teeth look worn in the picture so the gearbox sprocket could be the same or worse, and a new chain isn't going to last long on worn sprockets.
Click to expand...
Thank you for that advice. I guess if I get to replacing the gearbox sprocket it should be easy to get a new chain on.
 
Cuppy said:
I guess if I get to replacing the gearbox sprocket it should be easy to get a new chain on.
Click to expand...

Yes.:)

However, replacing the gearbox sprocket involves stripping the primary drive and does need some special tools either bought or made, especially a clutch diaphragm spring compressor tool. Don't try to strip the clutch without one of these.
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

Engine sprocket extractor
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
Clutch locking tool (useful but not always necessary)
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
 
I think I may be in real trouble.... It appears I may have a 16 inch rear wheel and tire. The hub looks right. Tires are Carlisle MT90-16 but I can't find proof on line they are in fact 16 inch. What can I do now?
rim1.jpg
rim2.jpg
 

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Cuppy said:
I think I may be in real trouble.... It appears I may have a 16 inch rear wheel and tire. The hub looks right. Tires are Carlisle MT90-16 but I can't find proof on line they are in fact 16 inch. What can I do now?
Click to expand...

The 16" 'chopper' rear wheel seems to have been a reasonably common modification.
Either keep it as it is or rebuild the wheel with an original 19" rim but perhaps wider than the original WM2 or 18" as that allows a wider choice of 'rear' tyre.
 
Cuppy said:
I think I may be in real trouble.... It appears I may have a 16 inch rear wheel and tire. The hub looks right. Tires are Carlisle MT90-16 but I can't find proof on line they are in fact 16 inch. What can I do now?
Click to expand...
Strip the rim from the hub and send the hub to http://www.buchananspokes.com/ They know Commandos and will do it right.

Get them to lace a 18" WM3. As LAB says, it offers you a wider choice in rear tires and the slightly wider (from WM2) rim fits modern tire profiles better.
 
Looking at the pictures I would be suspicious of the 5000 miles claim.

Without knowing its history there are a few potential failures that most, if not all, Combats suffer.

1 The main bearings. Mine failed at 4000 miles but others lasted a bit longer. They don't fail dramatically. You hear a rumble develop.

2 The tops come off the slotted pistons. These will almost certainly fail at some stage and can fail dramatically.

3 The layshaft bearing fails. Some will do a high mileage without failing but can be a dramatic fail when they do. You sometimes have a warning when the kickstart swings down as you pull away.

Sorry to be so pessimistic but it's better to know what may happen unless you satisfy yourself of its condition.
 
Alan L said:
I don’t know what others think but on first inspection of a few photos it looks like you’ve got the basis of a very good bike.
Best of luck and happy restoring and riding
Al
Click to expand...
Thanks Alan L. I believe it has potential even though more work than I was expecting having the Combat engine.
 
Nortoniggy said:
The tops come off the slotted pistons. These will almost certainly fail at some stage and can fail dramatically.
Click to expand...

"206709" should at least have the stronger pistons (without the slots behind the oil control rings introduced from 204166).
 
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