SC500, bit of a gearbox problem

After the SC500 locked up at the beginning of 2nd race at Clyro, I’d initially assumed that it might be the clutch problem I’d had at the end of last season, however it clearly wasn’t as the absence of neutral confirmed. Somehow I persuaded some of the guys to heave the bike back to the trailer whilst I was out on the 250 race.

Oh, what are these bits ?

Back in Bwlch and time for a quick look on Sunday night (along with looking at the MX250 problem that had appeared), as I knew I was on the road for 10 days. Removing the clutch cover revealed that a loose shim from somewhere, along with what looked liked the remains of a needle roller bearning. More pins/needles were found as I removed the clutch, but limited time meant that splitting the cases wasn’t going to be an option.

That evening got me thinking about spares and parts; unlike the 250, I’ve not really got any parts for the SC500, though the cycle parts are interchangeable with the 250. I’d missed some parts on ebay earlier in the year (part of the off-loaded Barry Townend collection). Engine spares I have none.

Whilst out and about this week, I found the time on the train journey between Utrecht and Frankfurt to have a quick look on the online spares catalogues that North West Vintage Cycle Parts and the only needle bearings are mounted into the crankcase and it maybe that these have failed, causing the problem. The good news, that the bearing is a common part with the MX250/360 (good old Yamaha) so may have a relatively quick fix. I’ve also scanned the parts book in attempt to preserve it. The North West pages has the advantages of direct ordering and a list of the superceeded part numbers.

It’s a week or so befire I’m back to the workshop, but it gives me time to mentally prepare for the worst scenario and a knackered shaft.

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