Classic Bike Guide

Losing your grip and clutch springs


The AS1’s clutch will be fitted with brand new springs regardless of what came with the bike/project/wreck. The normal arbiter for such springs is a relatively simple assessment of their overall length, which is said to be sufficient analysis of their viability. Sadly, previous experience with a very similarly designed and built Yamaha YL1 has convinced me that length is only part of issue. Even when these springs are within specificat­ion in terms of length, they can still fail in use, as very annoyingly proved with the smaller twin. Even when equipped with new friction plates, the clutch span up in top gear and slipped like mad under load. The only reasonable conclusion was that despite ‘being within specificat­ion’, the springs had weakened over time. Some detailed Googling has subsequent­ly revealed that being under pressure or tension for a protracted period can indeed reduce a spring’s inherent strength… so now we all know! Having had to rebuild the YL1’s clutch twice now, with two attendant partial strip-downs, has taught me not to compromise.

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