ENGINE IDENTITY.

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Re: ENGINE IDENTITY.

Postby Rob Harknett » Fri Oct 13, 2017 10:15 am

All useful knowledge John, also Robs comment about CS engines all being short stroke after 1955 ?? There, I've forgotten all ready. 55 ? But I and anyone else can still check literature. I am afraid in most areas of bike knowledge, I tend to forget a lot, but I do know where I could find the answer.

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Re: ENGINE IDENTITY.

Postby ajscomboman » Fri Oct 13, 2017 10:24 am

Rob Harknett wrote:All useful knowledge John, also Robs comment about CS engines all being short stroke after 1955 ?? There, I've forgotten all ready. 55 ? But I and anyone else can still check literature. I am afraid in most areas of bike knowledge, I tend to forget a lot, but I do know where I could find the answer.


But only in 500 cc capacity, the factory still continued to produce both short and long stroke motors in 350cc form. The long stroke being mainly for trials and the short stroke as a scrambler. All good fun delving into AMC history. It's not always clear cut as factory odd balls do crop up now and again but the history in the archives is pretty much spot on most of the time.

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Re: ENGINE IDENTITY.

Postby Rob Harknett » Fri Oct 13, 2017 11:44 am

ajscomboman wrote:
Rob Harknett wrote:All useful knowledge John, also Robs comment about CS engines all being short stroke after 1955 ?? There, I've forgotten all ready. 55 ? But I and anyone else can still check literature. I am afraid in most areas of bike knowledge, I tend to forget a lot, but I do know where I could find the answer.


But only in 500 cc capacity, the factory still continued to produce both short and long stroke motors in 350cc form. The long stroke being mainly for trials and the short stroke as a scrambler. All good fun delving into AMC history. It's not always clear cut as factory odd balls do crop up now and again but the history in the archives is pretty much spot on most of the time.


I just had a look at 350's that is a bit of a mine field. Some std road models short and long stroke. There's 81 mm 85.5 and 93mm strokes. Includes light weight 350 also. plus 347 & 348 cc. There are also literature errors?? e.g 56 / 57 349cc 7R, stroke 78 mm. prior to that 348 cc was 18 mm stroke, yes 18 mm that has to be wrong surely.
Ashampoo_Snap_2017.10.13_12h43m09s_001_.png

You also have to be careful how you read this literature e.g dates given, except for the start of civi production in 1945, early post war the calendar year was used. When the London shows started up again , they reverted back to the model year starting Sept 1st. To get the next year models read for the motor cycle show first week of Nov. So where you see Sept. 55 That's the 56 model.
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Re: ENGINE IDENTITY.

Postby bjorn » Fri Oct 13, 2017 6:56 pm

CS timing side roller bearing.JPG
CS crankcase.jpg
Roy,
The engine number and CS suffix are correct for a 1957 AJS "short stroke" 86mm bore x 85.5mm stroke.
As John Jarret points out, the timing side case for these engines has a roller bearing in addition to the oil distributor bush. See the enclosed photos.

As you probably are aware, the CS engines have different crankshaft/flywheels, cylinder, piston, cylinder head, cams, push rods, etc. than the standard long stroke models. Happy parts hunting!

Bjørn
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Re: ENGINE IDENTITY.

Postby GOLDSTAR » Sat Oct 14, 2017 4:55 pm

I am led to believe that the short stroke CS engine had the bottom end of a 7R, if this is so it does give you a little more scope to obtain parts, kind rergards

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Re: ENGINE IDENTITY.

Postby bjorn » Sat Oct 14, 2017 10:31 pm

As far as I am aware, the only component on a 7R crankshaft which was also used on the CS models is the crankpin.
Stroke for the 7R is 81mm prior to 1956 and 78mm thereafter, compared to the 85.5mm for the CS. Flywheels and axles are different and the 7R con rod is shorter than for the CS models.

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Re: ENGINE IDENTITY.

Postby GOLDSTAR » Sun Oct 15, 2017 6:49 am

thanks Bjorn, thats sorted it then, and come to think of it 'tis probably what I was informed. kind regards

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