Engine type and year?

[dennis.t]

I bought an engine bottom end recently and was told: "It is a 350 single". It is missing both the timing side and drive side parts so before I go buying parts would it be possible to confirm the engine type and year from the engine number?
The engine number is MA1219.
Lastly, if it is a 350, I have a 500 barrel but no piston. The bike is unregistered so could I build the engine as a 500?
Many thanks, Dennis

[will_curry]

You have a 1956 350 bottom end there.

The stroke of a 500 is bigger than that of a 350 so the flywheels
are different but the crankcases are the same.

To build it as a 500 you'd need not only a piston and cylinder head
but also a set of flywheels.

[Roger Gwynn]

MA 1219 is a 1956 NH delivered to Monmouthshire. You could build as a 500, many people have done in the past as the crankcases very by year but not by model. As it has been done in the past 500 bits are rare and expensive whilst 350 bits are cheap and relatively common. The 350 is perfectly good and only slightly slower than a 500, the difference will be felt when two up or steep hills. You will need a crank, cylinder head, carb, ex pipe and push rods, the other parts are the same as a 350.

[dennis.t]

Will and Roger,
Many thanks for the information. The bottom end is good so I will probably stay with a 350. I already have a VH500.
The 500 barrel was 'thrown in' by the seller so it cost me nothing. I like the sound of: "350 bits are cheap and relatively common"

[dennis.t]

Having taken the crankcase apart today I am now in a position to measure the conrod length. I want to make sure I have the 350 conrod because the engine came with a 500 barrel, not attached to the engine, and there is a slight chance that the engine has been modified to take the 500 flywheel and conrod. I should appreciate any guidance on how the conrod is measured e.g. overall length from the outer ends or something else?
Will the flywheel or conrod have a number or code to indicate if it is a 350 from 1956?
Interestingly (for me at least!), the engine plates have been drilled extensively to reduce weight and the engine and gearbox mounting bolts have been drilled expertly to take securing wire suggesting the engine may have been raced; some holes in the mag mounting plate spell 'SAM'.
The bottom end is in good condition but there was a full 70 years of hardened crud in the flywheel 'oil purifier'!!
Dennis

[Roger Gwynn]

See the flywheel and con-rod list from Draganfly https://draganfly.co.uk/wp-content/uplo ... umbers.pdf
Best to measure the stroke, even if the rod is 350 it could be in 500 flywheels

[will_curry]

Most 500cc con-rods I've seen have been marked A7/473 but I know there are
others: see https://draganfly.co.uk/wp-content/uplo ... umbers.pdf

Safest is to measure the stroke: 95mm for 500 and 85mm for 350. Except it's
not that simple - there were 85mm 500s in early post-vintage days and some
of the more serious Arielists have made short-stroke 500s for various purposes.

If it is a short-stroke 500 you have I'd expect the barrel to be somewhat shorter
than standard and to be opened out to something around 86.4mm bore.

[dennis.t]

Thanks for the replies. I will check the stroke. Also, I will check to see if there is a part number on the con-rod.
Dennis

[dennis.t]

I have now found the part numbers on the con-rod and flywheel. Thanks to Will's list con-rod code A7-339, is correct for an NH. Similarly, the flywheel code A7-920 also correct for a 1956 NH engine.
Many thanks,
Dennis

[will_curry]

Mmm. Not really my list, I simply passed on the link.

Roger did all the hard work here.