Hi folks,

I recently bought my son a 2006/7 DT125X. It had been advertised as being in original condition but, upon delivery, I noticed a bright blue wire leading from behind the headlight assembly to the chassis. I had previously read about a DIY bypass for the YPVS which entailed cutting a wire leading into the ignition block and earthing it onto the chassis and sure enough this is what has been done to it. I reinstated the wire as it should be as I think Mr Yamaha probably knows more about building bikes than I do but the YPVS did not work. Investigation showed that not only had the bypass been fitted but some bright spark had also cut the 5 wires leading from the YPVS servo assembly. I reconnected them and plugged them into the appropriate connector block. When I turn the main power on I can now feel a small click in the servo unit but it does not turn the pulley and perform a full cycle of the valve as I believe it should. It also does nothing when the bike is actually running. I have noticed a further 2 connector blocks which I assume should have something plugged into them? The bike is fitted with a CDi unit which is located under the petrol tank. Does this run the YPVS or should there be a separate YPVS controller (perhaps plugged into those 2 spare connectors)?

I do have a PDF version of the service manual for the bike but it doesn't say a lot about the YPVS other than how to adjust it. The wiring diagram is a bit too complicated for me to understand without some guidance.

Any advice would be gratefully received.

Regards

Hue

Aye hue " the power valve may be needing cleaned , or is worn , that be why some ass cut wires ,

I'm not sure whether the P.V. is cable operated on your bike but if it is , check the cables as they seize if not lubed .

Hi there sorry to resurrect a dead thread but did you solve the issue at all? I'm having a similar issue and like you say the haynes manual has little info on the workings of the YVPS system which is immensely irritating,

Cheers