any one the differences in these engine can i bolt mk3 into my mk2 and go is it plug and play , any info would be great

Ok I know for a fact that with a few simple mods a Mk2 can go in a Mk3.
The frame locations are the same other than the head which needs to be changed anyway

Differences.
The heads are different. If you want to swap a Mk3 head for a MK2 then PM me.

The wiring connections are different.
Luckily the colour coding is the same.
I have had to cut the plugs off and solder the connections. Just be careful to leave enough cable on the loom.

The neutral light switch has 3 wires on the MK3, the Mk2 only has 1.
I connected the 1 wire from the MK 2 to the same colour on the MK3 loom and the light worked. I don't know if this would work the other way around if you know what I mean. No big deal not to have the light anyway.

This is one of the big differences inside the engine that is the gearbox selector drum has a larger diameter on the Mk3 as it fits straight into the casing. The MK2 has a needle roller in the casing and a smaller diameter on the end of the shaft to fit into it. This was probably done to suit the different neutral switch.

The other difference I have found is that the clutch side of the MK2(possibly MK1) has a threaded end for a nut. The Mk3 has a tapped hole for a screw.
Hope this helps.

Just to confirm Eddie:

By - 'This is one of the big differences inside the engine that is the gearbox selector drum has a larger diameter on the Mk3 as it fits straight into the casing. The MK2 has a needle roller in the casing and a smaller diameter on the end of the shaft to fit into it.' Do you mean the shaft diameter is larger on the Mk3 .

And - 'The other difference I have found is that the clutch side of the MK2(possibly MK1) has a threaded end for a nut. The Mk3 has a tapped hole for a screw.' I assume this is the end of the crank

knackeredMk1 wrote:Just to confirm Eddie:

By - 'This is one of the big differences inside the engine that is the gearbox selector drum has a larger diameter on the Mk3 as it fits straight into the casing. The MK2 has a needle roller in the casing and a smaller diameter on the end of the shaft to fit into it.' Do you mean the shaft diameter is larger on the Mk3

.Yes the shaft diameter on the selector drum is larger on the MK 3 engine where it fits into the casing (alternator side)

knackeredMk1 wrote:And - 'The other difference I have found is that the clutch side of the MK2(possibly MK1) has a threaded end for a nut. The Mk3 has a tapped hole for a screw.' I assume this is the end of the crank

Yes