Setting up the PowerValve

  • Hi

    I have a 2001 DT125r and it hasent really been running right since i got it, its all fixed up now.

    anyways ive been looking everywhere for the best way to set up the powervalve, im sure that is what is causing it to not rev right through the range and throttle itself at around 6k -8k revs, the reed valve is removed so i dont think its that.

    at the moment there is no band either and still stops going any higher at 6-8k in every gear.

    any help would really be appreciated as its getting to the point where i dont even want to ride it as im stuck at 50mph on A roads.

    Alfie 🙂

  • Sounds like powervalve

    Quick test to see if it is.

    Take the exhaust off.

    Using the adjusting screws on the side of the engine. Move the powervalve so that it is flush with the exhaust port.

    Then disconnect the valve and test the bike. Should be low on power till around 6k where it will pick up right to the red line. If so voila, the powervalve needs setting up.

    Easy enough job.

    When you turn the ignition on, the powervalve iterates through a cleaning cycle where it will.go to max open and max close.

    By using fingers up the exhaust port. Turn the ignition on and off and feel how the powervalve sits. Adjust to a point where the valve turns to max open, and is flush with the port.

    This should line up with a mark underneath the powervalve cover. Although I prefer to feel how flush it is.

  • thankyou for replying, depending on the weather tomorrow ill do it then

  • @Calum ive done what you said, i disconnected the servo and pegged the valve open, bands at about 7-8k now which is what it should, did a speed run aswell and got it to 60 now, then i think the carb gives up.

    I may try upping the jet size to a 240/250 rather than the 210 thats in there now as i have a full dep too

    If that dosent fix it then ill probally do a carb swap with another one

    Got a new set of cables and a new pulley comming too so ill see if that helps

  • Upjetting to 240 sounds about right

  • 210 is absolutely fine.

    It won't be a carb issue mate sounds to me like a restriction you haven't taken care off.

    Ensure all the bottles are placed on the bike as they are there tk help. Make sure the snorkel is in. Do all the necessary derestrictions. Ensure there is notbing obstructing the flow of exhaust gases through the exhausr pipe.

    Make sure the engine is in good nick too.

  • @Calum
    It was the carb that was the problem, along with the valve, i will order new cables and pulley soon and see if thats it because the cables are frayed and pulley bends when being moved.

    the carb just gave out on me today, last month it was set up professionally, and fixed after my previous troubles.

    after a week i did a plug test and it was perfect

    however, even though i rarely ever use the choke, even to start it, today it just stopped working entirely.

    i did a plug check and it was completely fouled, so a new one was tried and it still wont start. (it did for a bit but idling really high)

    i have no clue where to begin, any help would be appreicated


    Alfie 🙂

  • Yeah no worries that what the forums here for.

    Firstly carbs don't just fail so don't panic.

    In order for the carb to be professionally setup they would be running your bike on a dyno. Failing that they would be doing runs up and down the street until it 'felt' right.

    The best thing you could do is set the carb back up as standard as Yamaha spent many hours researching jetting so you don't have to. Unless of course there is a reason why you should be runnning it.differently.

    If the plugs are fouled then it is more likely to be over oiling via the pump. Either the pump isn't setup properly or its broken. Despite this is should still run

    If it's not the oil pump then it may very well be the crank shaft seals. Or rather seal located inside the clutch cover.

    I would always replace the pair and its a crank case split job to fit. At which points it is always worth doing the main bearings and gearbox bearings.

    Obviously if this seal is gone iit will draw in oil from the gearbox.

    Easy way to check is to see how much oil is inside the gearbox. Although this would be very worse case scenario. Should just rule that out until we've investigated further first.

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