This thread is by way of a thank you to the Admin here for allowing me to download info I needed and because it may well be of interest to some here. I'm a Kiwi building mainly Classic and Post Classic race engines and sometimes complete bikes for the NZ scene, specifically the South Island. This project - half an FZR250 - is for the NZ Bucket class rules which in this instance require around 150cc and to be based on a road motor. There are allowances but pretty well everything used in this is road based anyway. The concept is not original to me. A gent known as Speedpro on Kiwibiker forum has built and is slowly developing a turboed and injected version. He will ultimately have to make it legal by reducing capacity to 100cc from it's current 125cc. I went what i consider the easier path of taking the engine out to 150cc and running unblown. I laid hands on about 1 1/2 broken 250 motors...by trading parts. Luckily the required side - the right - was good on one. So, cut the crank just past the camchain sprocket leaving 3 main bearings. From this point the crank oil holes were properly radiused and the crank linished. I'm using the 3LN long rods - and keeping my fingers crossed. To obtain the bigger capacity, I sourced a pair of low mileage GSXR400 pistons - early 53mm bore size. The gudgeon pin size is the same as the FZR.The barrel casting was cut just past the camchain tunnel and the liners pulled. I machined up new bigger liners and a friend bored the casting to suit. I installed the liners and he finish bored them. The camchain is 2 links longer also. Straight from the DID catalogue - a GSXR400 one I think. The pistons are approx 4mm higher deck height so a std base gasket, a 4mm spacer plate and a copper .020in head gasket, followed by a .010in cleanup cut on the barrel gave .032in squish. The head is also cut to match the barrel. The cams are swapped round end for end as the location is on the missing side of the head. New slots are cut in the head for the cam location. The lobes are symmetrical so running in reverse direction is not a problem. I'm using a std exhaust cam and a reground inlet. The inlet has a grind from the local guys Kelford Cams and is about .020in more lift and around 20 deg more duration at running clearances. i've put them in on 103/104 deg lobe centers which i know works on bigger FZR's. The inlet is not a buildup, it came out of the std lobe. Shimming was not excessive - biggest shim used was a 260. Still plenty of room before coilbind and the retainers are a mile away from the seals. Once I'd established the cam timing I could look at the valve cutaways. The Exhausts just needed moving a little closer together so they were cut using a die grinder. Plenty of depth on the cutaways too. I could actually have cut the head for more compression but it measures up at 11.8:1 - that'll do for a start. Pistons are 20g heavier than OE, we'll have to see if it shakes. Sealing the cut end was always going to be a problem. The wall thickness is thin so welding will inevitably distort things. There is some filler used to get a flat end which can have a plate screwed to it. The cut ends of the cam cover have rubber channel bonded to them. This is hard up against the cover plate. Will it seal well enough, we'll see... Speedpro's version uses the stock waterpump exit pipe going out and around. I've changed the pump exit to a tangential one for a short hose up and across the back of the block. Bit tidier - and importantly for me, narrower. At this point I'm planning on stock ignition, run total loss. I've cut the stock rotor but have yet to do a narrowed ignition side cover. I was planning on a scratch built frame - I build frames too - but have since been offered a race prepped FZR250 chassis complete with slicks and spare wets. It is of course at the opposite end of the country... Got to put it aside for a while and get on with paid work. More as it progresses.