the new thread things would have caught him out good spot - as my 1200 had a 120Y motor in it when I got it I didn't notice the different flywheel bolt threads, now I know why.

1966-1973 A-series engine
1973-2007 A-series engine
Different flywheel bolt threads

im nearly certain the a14 head and a15 head are very similar
this is what the bible says

Intake Ports
Round port 28mm: A12
Round port 28mm lowered: A14 GFU
Small Oval port 28x30mm: A13, A12A
Medium Oval port 28x34mm: A14
Large Oval port 30x34.5mm: A12GX engine

it doesnt say much about a15 there

i typed cylinder head into the wiki

One more question. On a closer look it has a round port head on it, should,nt it have an oval port???

This has been heaps of help. I,m sure I have most of the old a12 parts about so should go together ok. Thanks

The problem you're most likely to have is the B110 A12 flywheel bolts have a different pitch to the B210/310 A12 & A14/15 bolts. Hopefully the bolts for the A15 are still there, if not you might have to scavenge them from another motor. The bolts should run in by hand easily. If they only go in a short way & tighten up, they are the wrong pitch. Don't be tempted to run them in with a rattle gun, as this will make the crank unusable, by damaging the threads. There is also an offset bolt hole, so the flywheel can only go on in one position. If only 4 of the 6 bolts start in, it's the wrong position. keep turning the flywheel til they all go in. Naturally the right position would have been the first one you'd have got if you turned the flywheel the other way.

I'm running a A12 flywheel that was lightened to 3.8kg on a A14.

Bolt pattern is the same.
The only problem I had was the release bearing.
I had to extend the pivot point that the fork pushes on outwards to enable the bearing to move enough to disengage the clutch as I did not have different length release bearing carriers to play with.

Hope this helps a bit.

yea i got stung buy the flywheel problem just recently ... the A15 flywheel is thicker and you wont be able to get the clutch cable on if you use the wrong clutch fork and bearing carrier. some a12s also have a smaller pressure plate and the bolt pattern is different so i'd recommend just using the flywheel and clutch off the old motor

I have an A12 flywheel on my A15, bolt spacing is the same.
Good point re thrust bearing carrier A14force. If he's running A12 fly, clutch, bearing, starter and box, I suspect all will be well.

If you use the thicker flywheel, make sure you use the correct thrust bearing carrier for that flywheel. If you run the wrong thrust bearing carrier, even with the clutch fully released the thrust bearing will still be pressed against the pressure plate far enough that the clutch plate wont be able to drive.