MX250, back to the track

With work (and therefore travel), I’d not really had the chance to get the MX250 sorted since coming back from Belgium. The Yamaha had stopped running at the Lille track and I’d not had a chance to look at why. Also, with Llangorse Lake shut because of a blue-green algae outbreak, also not been able to go sailing. Time to spend some time in the garage.

I’d had a 0.50 oversize piston in the stock for a while, so got the rebore done Joe Lyon’s in Brynmawr (next day, £20.00 so no complaints) on one the barrels. I’d got 4 barrels, 3 of which had been polished so should therefore also be tuned.

Also, the replacement exhaust had arrived from Kevin Falle at Circle F in Houston (via Atlanta). If you can find a decent shipping route, these exhausts are reasonable ($200). I’d ordered them in February, some a longer than anticipated delivery time 🙂 Nice piece of work and decided to paint them with clear heat-resistance laquer. Not an easy product to find, and tracked down to Car Care in Monmouth; thanks to Chris Kent for the tip.

Circle F pipe fitted

The SC500 engine build still needed completing (more of this to come) but onward with the 250. Fitted the new barrel and piston, along with the cylinder head I’d been using. However, bit of kicking didn’t make the bike go; spark and some fuel, but nothing. The exhaust looked good, but nothing.

Hmm, frustrating. So after a cup of tea, re-laying some of the stone work in the back garden, decided to fit the other engine, with the barrel and piston I’d used in Belgium. The small-end bearing was a bit slack, but it fired up after a couple kicks. Exhaust sounded as good as it looked and engine ran okay, if not a little loudly. I’d swaped ignition, carb, piston, barrel, etc in the search of a work solution and having spare components around makes all the difference.

Yamaha kickstarts 1 Boots 0

Other jobs then got in the way and left it with the newly bored barrel and replacement piston in the bike, but with it not running quite right. Maybe it’s the reed valve or the head; ah well more research to come when I back in garage.

Off to Rome for work…and some sunshine at least.

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