Westwood S1600 transmission belt replacement ?

Hello wonder if anyone can help, I have replaced the transmission belt on my Westwood S1600 but there is a spring which fits onto the tensioner plate but I can’t work out how. The mower drives better with new belt but not how it should, I am thinking it’s got something to do with the spring.
Any assistance with this problem would be gratefully received
Thank Graham
Graham Kent, April 2020


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