Hi Y'all,

More of a discussion topic (and some learning for me) than a specific technical question, but...

Of the traditional engine, pre-unit, 4 speed bullets which I understand were manufactured between the 60s and the early 2000s, what (if any) distinguishing features do the engines have? Either external/visual differences and/or internal differences that could date the bike/engine? Obviously engine numbers/VINs will give it away, but that's no fun. And I'm not really interested in body work, accessories or colours...for context...

I've recently finished building this 500, 4 speed, pre-unit...and not much of the stock bike is left. I am thinking about seeing if I can race it in my clubs vintage class next year. The class doesn't have a defined "cut off date" for the age of bikes, but rather a "spirit of the class" rule that is determined by some of the organisers. The age of my motor might not class it as "vintage" but the technology sure would! So I am just interested in the actual differences in the motors from the 60's, 70's, 80's, 90's, etc. I'm not trying to deceive my club or anything, I'd be straight with them if I ever entered.

Just wondering how much of an RE expert you'd need to be to tell the difference between different years of the same model...can anyone date my bike from looking at it???

Looking forward to hearing folk's thoughts,
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Where do you begin? I assume you're talking about the Indian-built Bullet engines, the UK Bullets ceased production around 1961.

The Indian factory didn't produce a 500 engine until 1989/90, 350s only until then. The 500 has extra angular finning around the exhaust port for quick reference. Pre 1978 the Indian Bullets would also have had an English Bullet type pressure release valve on the front of the crankcase under the oil feed pipe to the rockers, as well as (less obviously) imperial instead of metric crankshaft main bearings. Pre '78 the timing gears were also used for the oil return to the tank from the timing chest, the crankcase and the timing covers on the inside are like gear pump housings. Late timing covers have the tab cast in to assist removal by clouting with a piece of wood from behind the engine, instead of leaving owners to try and pry the thing off with a screwdriver and possibly damage the joint faces.

There are chassis differences too over the years.

The crankcase breather stub on "original" bullets is a seperate bolt-on casting. The indian ones have it cast into the crankcase. Later ones have the stub with no hole in. Very late ones don't even have the stub.

Your bike has a full-width, twin-leading hub on the front wheel. Pretty sure older ones either had a half-width or double sided front brake.
Not sure, but I think the earlier Indian 500 Bullets had 2" carburetor stud centres until about 1997 then they went to 58-60mm(?), the 350 stuck with 2". Also can't remember what year the PAV started being fitted to the exhaust pipes.

While on the subject of running gear, the pre-1988 forks had separate screw-on oil seal holders like the UK-made RE items, but have we missed any differences regarding the engine? This was the original question. You could add increasing use of metric fasteners, not immediately obvious.


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