However, some time at home meant time working on the bike (along with other projects, like the DT175 ). I’d got a rolling chassis after getting a new rear wheel rim made up in Belgium and put in the bottom end of the engine.
The piston’s for the YZ250 are indeed the same that I’d used for the MX250 (the later 509 piston, with the cutaway rather than the boost ports)
The jobs that got done:
– barrel and piston; there is now nowhere in Hereford that can (or wants to) rebore a two stroke piston. Hereford Rebore has retired (he’d checked out a while ago though) and Phoenix Engineering doesn’t have the kit and are also down sizing. Nearest options are Ledbury or Brynmawr. Anyway, stuck with the original Wiseco piston for now as their didn’t seem to be too much noise.
– no spark on reassembly and spent 3-4 hours checking and cleaning connectors; also cleaned up the stator and rotor which had seen some water ingress at some point. Going for a cup of tea and coming back to find a spark was nice and reinforces the ‘take your time and don’t stress approach’.
– fitting the cables; I’d borrowed the ones I’d order for the MX250 as both the clutch and throttle had become a little worn. This turned out to a bit a faff to get the adjustments right and just took longer than expected
– ended up making a new bracket to go under the seat to hold the rear mudguard in place. Some expensive (well I though so) black coated aluminium from B&Q did the trick. Used some nice bolts from the written-off KTM 950 as the fixings (doesn’t this mean its not twinshock eligible now?)
– the carb and air filter box went together okay though the float height still needs doing.
– got the SuperTrap exhaust back off Alan and will use this on the bike for now to see how it goes.
Managed to get in a few laps of the field and the bike seems good. Need to set up the front forks a little better and change the oil, but the fork tops have been mangled in the past, so might be a challenge.
– get the airfilter to fit; the one I have is from a 78 YZ250 E and needs some modification
– do the plastics, vinyl and numbers.
– iron out any other small items, like the cable routing and ties
– check all the bolts and make sure they are tightened and correct.
PS: ended up getting up at 6am to finish off the bike and now pondering whether to give it an outing at Pontrilas this evening as they have a practice session today
Looking good and a relatively straightforward project that seems to have taken ages.