A few years ago I picked up a cheap MC21r in pieces, the plan being to build a cheap track bike. Since then its pretty much stayed in pieces.

I picked up a MC16 F3 engine a while ago with the idea of using this in the track bike, http://nsr250.net/forums/viewtopic.php?t=11230

The plan is to get her up and running for the Donnington track day in July so I have finally got my arse into gear and made a proper start.

I stripped the engine some time ago so all the bits went for vapour blasting and plating.

If you read the previous thread on the F3 engine you will see I had a couple of issues to sort out. After a tip from Andy I sourced a set of MC18r2j engine cases from Johnymac. These fit the mc21 chassis and the mc16 crank but needed a bit of machining to accept the F3 ignition.

I had the corroded hose spigots on the cylinders replaced with some nice stainless ones.

And had an mc21 water pump drive shaft re-ground to accept the mc16f3 drive gear.