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Combat engine C Stamp location?

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Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017

Hi everyone, 

I'm back again with my newbie questions. Sorry! 

I'm looking into buying a 1972 interstate, and I have asked the seller to locate the C Stamp, as the vin of the bike is clearly in the range of the Combat engine. : 209713

Is there a simple way of explaining where it is?
he sent me photos, but I can still not see it, and he can't see it.

Any help would be appreciated!
Thanks!
Rich

Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017

photos

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Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017

photos.. sorry, for some reason, it won't let me attach more than one photo ata time.

Attachments

Re: Combat engine C Stamp location?

Posted by gerard_senior at March 09. 2017

Hi Richard,

It's stamped on top of the head near the front but is very helpfully covered up by the head steady making it almost impossible to photograph!!!!! It should have 32mm concentric carbs (when new).

The engine breather exits the rear of the crankcases (when new)

Apart from the barrels being painted black (when new) I can't think of any other means to identify a combat engine just by looking but I expect the experts on here may know more, i would be interested to learn of any other means.

All the above items can and probably have been changed over the years except the "C" stamp ,(which you can't see) welcome to planet Norton.

Re: Combat engine C Stamp location?

Posted by richard_payne at March 09. 2017

The combat engine had the head planed to increase the compression.  Although it is not possible to say if it was done by the factory, it's quite clear when viewed from the side if this has been done.

If it's a wombat,  there will be very little gap between the top fin on the cylinder and the lower on the head.

Do you have a side on view of the top end ?

Re: Combat engine C Stamp location?

Posted by john_holmes at March 09. 2017

A combat from within the range would have also had a disc brake, all non combats were drum during the combat period. If you wanted a disc brake then you got the brake and the combat engine. For some reason most (if not all ?) of the Interstates from the period were combats. As all the changes could be added later then you really need to see all the clues.

1. In the right serial number range

2. C stamped on head

3. Planed and ported head

4. 32mm Concentric carbs

5. 32mm to 32mm manifolds

6. Disc brake

7  Black barrels

8 The high lift cam

Once you have the mains sorted and the oil return pick up relocated from the front to the rear its a reliable engine.

Combats and non combats in 72 all had the breather at the back, no sump filter and the oil return pick up from the front.

Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017

Maybe this? The closest pictures I have from seller.

Other photos too big for this site upload.

 

 

Previously richard_payne wrote:

The combat engine had the head planed to increase the compression.  Although it is not possible to say if it was done by the factory, it's quite clear when viewed from the side if this has been done.

If it's a wombat,  there will be very little gap between the top fin on the cylinder and the lower on the head.

Do you have a side on view of the top end ?

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Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017

As a soon to be owner of the bike, from your list, numbers 1, 2, 6, 7 are all on my "soon to be bike".

Others will need to be checked when bike arrives.

The bike also had a rebuild, tho not sure what was done apart from pistons, rings and cam.

How do I upload bigger images on this site? I have photo of the rebuild...

 

Previously john_holmes wrote:

A combat from within the range would have also had a disc brake, all non combats were drum during the combat period. If you wanted a disc brake then you got the brake and the combat engine. For some reason most (if not all ?) of the Interstates from the period were combats. As all the changes could be added later then you really need to see all the clues.

1. In the right serial number range

2. C stamped on head

3. Planed and ported head

4. 32mm Concentric carbs

5. 32mm to 32mm manifolds

6. Disc brake

7  Black barrels

8 The high lift cam

Once you have the mains sorted and the oil return pick up relocated from the front to the rear its a reliable engine.

Combats and non combats in 72 all had the breather at the back, no sump filter and the oil return pick up from the front.

Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017
http://imgur.com/a/NQRhI Here is a photo of a photo of the engine being rebuilt a few years ago. Could you guys take a look and see what was done? Thanks!

Re: Combat engine C Stamp location?

Posted by ian_goodhall at March 09. 2017

To me it looks like the head has been skimmed like the Combats were. The C on top is very easy to falsify. There is no easy way of deciding much else from those pictures re' camshaft etc.

The fuel tank is wrong. There should only be one stripe on a 750 tank and looking at the picture it looks like one of the narrower Interstate tanks fitted to later bikes. There were a few different shapes over the years, and then the Indian tanks.

The exhaust rings are wrong for a 750 too.

These things probably won't effect it's rideability but if you want it to be as original it's worth knowing what you're getting.

Re: Combat engine C Stamp location?

Posted by richard_chan at March 09. 2017
Here are a few more pics. http://imgur.com/a/MQS3O http://imgur.com/a/GQsdd http://imgur.com/a/BFwip It's why I love forums. There are always people that knows better. Feel free to spot the faults. I know the exhaust are wrong, handle bars, fuel lines. I would be very interested to hear what else. The price is ok for me, it's just under 10k€, which from what I've seen is ok out there?

Re: Combat engine C Stamp location?

Posted by john_holmes at March 10. 2017

An Interstate tank from 72 would have been Fibreglass and useless with E5 petrol so a later steel replacement is good, can't tell a lot else from the pics to add to Ians other than the rear tail light is off a later bike and the front mudguard stays should be silver not black. Where is the engine breather off the back of the crankcase and then going vertical, it looks to be missing ?

Re: Combat engine C Stamp location?

Posted by david_evans at March 10. 2017

The pistons shown in the rebuild photo are the early slotted type. these can crack if thrashed hard, saying that i have had a pair of these pistons in my Commando for 35 years and they lasted well. I think if you are going to explore the 6-7000 rpm range on a regular basis you might want to fit later pistons, normal cruising at 70mph is about 4200rpm

Re: Combat engine C Stamp location?

Posted by john_holmes at March 10. 2017

There are 2 versions of the slotted pistons, 1 is ok, the other is not. The bad version has a full slot, the good has partial slots but the pics are not good enough to see which version is fitted.

Re: Combat engine C Stamp location?

Posted by richard_chan at March 10. 2017

Hi,

I asked the seller, tank is steel.

Re: breather, is it as attached photo?

 

Previously john_holmes wrote:

An Interstate tank from 72 would have been Fibreglass and useless with E5 petrol so a later steel replacement is good, can't tell a lot else from the pics to add to Ians other than the rear tail light is off a later bike and the front mudguard stays should be silver not black. Where is the engine breather off the back of the crankcase and then going vertical, it looks to be missing ?

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Re: Combat engine C Stamp location?

Posted by richard_chan at March 10. 2017

Another side view

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Re: Combat engine C Stamp location?

Posted by richard_payne at March 10. 2017

I'll stick my neck out and say that it doesn't look to me as if that is a 'planed' Combat head - The gap between cylinder and head fins looks too large.

Re: Combat engine C Stamp location?

Posted by john_holmes at March 10. 2017

Re: breather, is it as attached photo?

That pic is of the correct breather for a 72, but its missing from all the other pics, maybe the pipe is currently disconnected, if it is disconnected it cannot run until it is reconnected as the breather will just deposit oil over the rear tyre.

Re: Combat engine C Stamp location?

Posted by richard_chan at March 10. 2017

Uhm. Maybe the pictures are not in a clear view.

The seller sent over a video of the bike running, seems to sound fine. Maybe a valve adjustment. There was no oil pouring out over the rear tyre.

He said the breather was well hidden away.

Re: combat engine - still no C stamp found. I think either way, this will be my big project for the next couple of years. I've just spent 8 months restoring a 74 RD250, that's done now, and new project begins.

Can't wait to annoy you guys more with my newbie question on one of my dream bikes to be.

Thanks again.but please, anyone spot anything different please let me know, I'm always interested in knowing what I got and what I'm missing.

 

Previously john_holmes wrote:

Re: breather, is it as attached photo?

That pic is of the correct breather for a 72, but its missing from all the other pics, maybe the pipe is currently disconnected, if it is disconnected it cannot run until it is reconnected as the breather will just deposit oil over the rear tyre.

Re: Combat engine C Stamp location?

Posted by Alan Throssell at March 10. 2017

Hi Richard, I hope you get the Commando, it looks a nice bike.

For information here are photos of my Combat engine No. 206--- It is presently out of the bike. You can see the faint C stamp on top which is normally covered by the head steady. The Combat head has 0.040" skimmed off to give a higher compression ratio, this only makes the head to barrel fin gap 1mm closer than a standard engine (not much different to look at).

Regards, Alan

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Re: Combat engine C Stamp location?

Posted by richard_chan at March 10. 2017

Hi Alan, 

Thanks so much for clearing that up, now I know where exactly to look!

Re: Skimmed head - Is there a measurement from the NORMAL barrel fin gap? If i know the measurement, then I can take a look and be sure mine is or isn't a Combat bike.

Thanks again for the photo. 
Rich.

Previously Alan Throssell wrote:

Hi Richard, I hope you get the Commando, it looks a nice bike.

For information here are photos of my Combat engine No. 206--- It is presently out of the bike. You can see the faint C stamp on top which is normally covered by the head steady. The Combat head has 0.040" skimmed off to give a higher compression ratio, this only makes the head to barrel fin gap 1mm closer than a standard engine (not much different to look at).

Regards, Alan

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