Gary Flood probably did race one, no doubt modified, but that seems to be about the time he ceased racing 125s.Ī 250 top end bolts onto the 125 pursang bottom end & is a very competitive bike if you wanted to go in that dir'n. The Mk8, tho an entirely diff barrel, had similar inlet port to Mk6 &7, & none of the MK6,7 or 8 had the piston skirt probs of the Mk5 IIRC. The Mk7 used the same barrel as Mk6, but lost a lot of weight, had closer ratio g'box & I believe less flywheel weight than Mk6 (but more than Mk5) & were almost competitive, so they can be made to work. The Mk6 actually had much better porting as they also added an extra pair of transfers & they make decent power but cos of the flywheels they were considered rather slow & by then were also overweight for a 125 so they were not very competitive.
They changed the inlet port design on the Mk6 to an unbridged one with 'dished' (concave) bottom but also took the extra precaution of adding considerable flywheel weight. So for Mk 6 they 'solved the problem' by putting large (for a 125) flywheels on it which made them feel slow.īut I'm lead to believe the problem was the bottom of the Mk5 inlet port was flat, & even tho bridged it caught the skirt at very hi rpm. Their claimed max power was at 10,500rpm & at that rpm rear piston skirts broke - probably when you missed a gear. The Mk5 before it was fast & 1 of the 1st 125s to have little/no flywheel, but they were unreliable.
They were a bit dated when they came out- mainly cos of weight.
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