Hello All - my first technical post here, so please be gentle. I am just starting to strip down and rebuild my dt125r 1993 (3rn6) engine that I shall be using in a project bike. On examination, the 3MB00 cylinder that is fitted is a unit which has a powervalve that is fixed in position and has no servo unit or cables etc to move it round.
My questions are:
Is it possible to and are there any benefits to trying to retro-fit a powervalve control unit to this cylinder? What exactly would be involved? Can anyone quantify what the benefits would be?
Is the servo unit controlled soley by the cdi or is there anything else that comes into play?
Having done some searching about on the forum and elsewhere, I see that some change the fixed position of the valve which seems to have some benefits and at the same time some drawbacks.
I understand the reasoning for having the servo controlled powervalve but can see that it does add complication to the engine wiring etc, especially as my engine is not actually going into a dt. I am going to be needing to make up a loom from scratch on my project.
Thanks for explanation Andy - so will the 3 wire servo unit work alongside the cdi I have from 1993? Also, does the servo unit bolt to the barrel and existing powervalve without further modification/new parts?
Where do the three wires head off to from the servo unit?
Sorry if these are silly questions but I am more used to two strokes that have fixed exhaust ports and much less wiring than these!
All the best, Tom
-- Edited by swallow on Tuesday 15th of January 2013 08:47:37 AM
Static - some people turn the Powervalve slightly to give a medium between the two.
Servo - There are two types. The 3 wire and 5 wire versions. The 5 wire version needs a Powervalve control unit to operate. In later Cdi from 1999 onwards the control unit is built in. Otherwise you need the rare control unit that is seperate.
The 3 wire unit has the power valve control unit built in and was sold as an upgrade from 89-96 97-98 bikes had them fitted as standard.
I have the 3 wire unit for sale for 68 quid delivered if you are interested.
The servo unit mounts onto the frame on the DTR underneath the petrol tank with two bolts going into static nuts on the frame. I can't see why there would be an issue with mounting it to somewhere else on another bike, the only issue you will face is with the length of the cables that will run from the servo to the pulley wheel on the side of the barrel that turns the valve itself but you could get these made up if some of the original cables werent suitably long enough.
The three wire servo has three wires coming directly from the servo as in the photo below. Two go to a connector block and 1 goes to a bullet connector.
They then join to the main loom or maybe straight from the CDI? I cant remember but theres a diagram on here in the electrical section that should show you. Or in the haynes manual.
