THIS month's surge in Hong Kong shares yesterday triggered a 4.11 per cent jump in Shanghai's B-share index as investors returned to China, according to traders. ''Investors are once again showing an interest in B shares and asking whether now isn't the right time to buy,'' said Julie Leung, a China analyst with Sassoon Securities. Hong Kong's Hang Seng Index, which includes many companies with China projects, has risen about 15 per cent this month, while prices of Shanghai B shares are more than 30 per cent lower than at the beginning of the year. The Credit Lyonnais B index closed up 30.88 points at 782.02 on healthy turnover of US$7.33 million, compared with $6.9 million on Friday, according to Bloomberg. The A-share index, however, lost 45.15 points, or 1.39 per cent, to close at 3,199.07. Yesterday's rally was led by Shanghai Tire and Rubber, and textile machinery manufacturer Erfangji. Both gained more than 13 per cent after lagging behind the market in recent weeks. Erfangji, which makes dyeing and textile machinery, closed at 34.6 cents, with 226,000 shares traded. ''The sell-off looks like it was overdone, and right now Erfangji is pretty cheap,'' a floor trader said. Tire and Rubber shares surged 13.3 per cent to 58 cents, with 903,000 shares changing hands. Bicycle stocks Forever and Phoenix also made strong gains, especially Forever, which generally lags behind its more popular rival.