another perfectly good motorcycle ruined.......

Sunday, 7 February 2010


some you win, some you lose, all revved up about getting the engine back from the tuner's, lets get it bolted into the frame and go racing, bolt rear shocks in and stand back to admire, bollocks, the left hand shock is leaning in by 10mm at the swingarm end, measure, measure, measure, no way around it, must have been a friday afternoon job, the bottom shock mounting has been welded 10mm off centre, i've already fitted the new swing-arm bushes, the arm has been powder coated, double-bastard, need a new swing-arm [ later models are a lot beefier], or cut mounting off, re-weld and powdercoat the original, no way around it, got to do it or it will handle like shit.

that's better, thrown those ugly engine mounting plates in the bin like uncle abner loveless said and got a pair of burwins modified ones instead, they are beefy buggers for sure, the one on the right is the drive side which should stop the tuned motor twisting in the frame.

one thousand, four hundred pounds worth of race tuned mz engine, lot of money?, not when you break it down, 50 hours of labour, machining, measuring, checking, parts, carriage, barrels shortened and ported, port floor built up and re-shaped, wiseco racing piston, crank rebuild, close ratio gearbox, new selectors, pvl racing ignition, hand made expansion chamber, lightened clutch assembly, serious bit of kit, standard 13bhp, this baby 30 to 33bhp.


the top three fins on the head have been removed, they weigh a kilogramme each, the rubber mountings are daf lorry parts to damp out vibration and lower the engine in the frame to give a better c.o.g., the tiny brass tube drilled into the float bowl on the carb is for a breather to stop fuel cavitation, the original drain from the float bowl will exit into the frame catch tank but if fuel reaches it then the carb will lose atmospheric pressure and not breathe correctly causing poor carburation hence the modified breathers.

the carburettor has been bored out to 33mm, this is the maximum you can go to without weakening the casting, theres a whole lot of work in the carb, the baffle shoulder needs shaping to give a good air flow, the fuel passages need massaging and the cross drillings need to be worked, the carb is very primitive but the regs state that this is what you have to use, shame really, a nice big hsr 42mm mikuni would give loads more power.

the barrels have been shortened which means that the carb manifold has to be re-angled to clear the crankcases, the fins on the back of the motor have been trimmed back to give some space to machine the rear of the barrel to mount the carb.

this is the pvl racing ignition, £170's worth of electrickery, the kit is basically a magneto, the rotor and stator forming the generator and a high-output coil supplying the big fat sparks needed for performance, the pvl system is used extensively in classic bike racing.