LCGB Forums

I'm going to rebuild/upgrade a Series 1/2 engine and was wondering if there's any point/benefit in changing the drive sprocket spring to the longer Series 3/GP spring and cap/washer?

No harm in upgrading I’d suppose

What is to be gained?

That's my point but they must have changed it for a reason...

If you upgrade the spring you will also need a deeper side case. The spring was changed due to being not strong enough.
The sprung clutch centre also was eventually changed to a solid type due to frequent failure.
The early flywheels also had to be revised because the alloy fan was fixed to the brass centre by roll pins around the circumference. These of course came outwards under centrifugal force and dug into the flywheel housing. This gave the impression of a seized solid motor.

petemaisey wrote:If you upgrade the spring you will also need a deeper side case. The spring was changed due to being not strong enough.

Why is this.I thought the sleeve and spring cap were the same length on early and late models.

The Ser 1 spring cap is shallower to go with the shorter spring.

If the series 1 spring cap is shorter then it would sit deeper in the crankcase,each side case is the the same depth.I have just built one with a sidecase that has 6mm holes for the exhaust studs,this uses a series 3 crankcase with a series 3 sleeve and spring cap.