Identifying a Combat motor

batrider said:

Combat valve specs are .008" for inlet and .010" for exhaust. You could check valve lift to see if it is the 2s cam. The rocker ratio is 1.13:1.

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Stephen Hill said:

The valve clearances won't help you identify the cam.
You will primarily be measuring maximum cam lift.
Details found here: http://atlanticgreen.com/camsurvey.htm
I went through this recently. Fortunately I had the head off and which meant I could disregard rocker ratios and read lifter motion directly. I still found it fiddly.

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Karl Johnson said:

Thanks for that. I'm thinking it may be best to simply wit until something happens or necessitates to need to pull the motor and split the cases. The mystery would be solved then.

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Fast Eddie said:

The 2S (Combat) cam has a lot more lift on the inlet vs the exhaust, so a quick way of ruling out a standard cam, and indicating a possible 2S cam, is to check if the inlet has more lift than the exhaust.

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Karl Johnson said:

Hi Folks. Kinda of a strange question, but here I go. A few years ago I bought a very much incomplete basket case 72 Roadster project that supposedly had a Combat motor. Hard to confirm the Combat motor, but it did come with a Combat head. Long story short, at the time I split the cases and replaced the bearings, etc. I neglected to check which camshaft was in there. Question is....are there ways to confirm whether the camshaft is a 2s without tearing down the motor? For the last couple years is been back on the road it's been really reliable with the twin Amal 932s and is happy with the valves set to .06/.08. I am aware that the Combat motor is meant to have the valves set to .10/.10. Haven't tried loosening them up to check. I'm thinking I may have a standard Commando cam in there, but thought I would see if there was a way to confirm. At the end of the day It doesn't matter to me. Just curious more than anything else. Thanks

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B+Bogus said:

One other less scientific method:
Does it take off like a scalded cat at 4k rpm?
The power delivery with a standard cam is fairly linear, whereas the Combat has a very definite surge around 4k (from memory - it may vary slightly one way or the other)

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marshg246 said:

If happy with bike, I would simply assume 2S, set the valves accordingly and not think more about it until you one day split the cases. As several have said it likely can be determined but you also have to consider that someone could have put in a 4S or any number of aftermarket cams so without more precise checking you still won't really know.

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