The lift problem is probably the age of the machine. You have an alternate path through the control/spool valves and or the tilt cylinders. The previous advice about hiring an experienced professional is solid advice. Understand Clark has never been a stable company and of sound engineering practices. By that I mean they utilized very strange technology; whether converting a diesel engine to propane or using wet brakes inside the transmission. Clark has been sold, gone out of business, etc. many ti mes. You will need a very good mechanic for this unit. The average forklift mechanic will have his lunch eaten by an odd Clark design. You need to evaluate the mechanic you choose carefully and understand it may cost a lot to repair. Also you may not be able to get parts.