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P150 pick up, acceleration and top end problem

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  • P150 pick up, acceleration and top end problem

    Dear fellow riders and xperts.

    I have a Pulsar 150 DTS-i UG3 digital console bike, had done around 60,000 kms and is abt 3.0 years old. My bike has a peculiar problem, after say 70 kmph there is no or very little acceleration and the bike feels as if there is some kind of electronic lock installed which is not allowing it to accelerate. if i continue riding it this way for quite some time the bike will slowly pick up speed and then between 80kmph and 90kmph a point is reached when suddenly the bike shoots like a bullet, reaching 100 kmph in no time. if there there is a slight incline in the road or heavy wind and the bike is not able to reach sudden acceleration point its speed will be stuck at approx. 80kmph. the point of sudden acceleration is not fixed sometimes it happens at 83 kmph sometimes it happens at 90kmph. before that point of sudden acceleration there is very little pick up from 70kmph to 80kmph.and the kind of acceleration it gives after that point is unbelievable for a 150cc bike. it shoots like a bullet.


    history of bike --
    • just changed clutch plates and silencer and hose pipe between carb and filter box. ( the problem was there before these changes)
    • i regularly do all my servicing at every 2500 kms, use good quality oil and barhdall.
    • i had modified my bike's stator plate for HID by rewinding.
    • had changed block piston, clutch plates, repaired crank shaft 1.5 years back.
    • had a mojor accident few years back, in which chasis broke and replaced. ( all repairs properly done at authorized service center, and bike was working fine untill recently)
    i love my bike, kindly help.
    sigpic

    Tyre Sizes _ Spark Plugs

    Headlight Focus _ Fork Oils

    All India xBhp Couple Riders Thread

    Ashtavinayak + Shirdi
    Purandar
    Raigad
    Dapoli
    Aurangabad
    Kaas Plateu & Thoseghar Waterfalls
    Purandar

  • #2
    Query Approved.
    :)

    Comment


    • #3
      help me

      c'mon guys help me sort out d problem.
      sigpic

      Tyre Sizes _ Spark Plugs

      Headlight Focus _ Fork Oils

      All India xBhp Couple Riders Thread

      Ashtavinayak + Shirdi
      Purandar
      Raigad
      Dapoli
      Aurangabad
      Kaas Plateu & Thoseghar Waterfalls
      Purandar

      Comment


      • #4
        Very interesting problem i have to say. I can think of two probable problems but i may be wrong

        1. Your carb the jet needle is not rising as it should. Probable resons are choked air vents or wrongly installed diaphragm or leak from the top of diaphragm . Try sevicing your carb.

        2. Ignition timing not advancing or very retarded timing. something wrong with the CDI unit i don't know much about it.
        BTW Did you re-wire your stator before or after this problem, if before then how many days before. Did you disturb the rotor also.

        Also what is the RPM at which it stops accelerating and what happens in the lower gears at the same RPM, like in 3rd gear.
        How is your mileage as compared to before.
        Is your exhaust bend yellow (discolored due to heat) from the engine to a more distance than other similar bikes amusing you have chrome exhausts.

        Comment


        • #5
          Also when you are stuck at 70 at full throttle try reducing the throttle slowly a see whether its accelerating better or worse.

          Comment


          • #6
            There is a reed switch mounted on the Carb and as you turn the accelerator it alters the CdI timing. CHECK IF THIS IS FAULTY. On zero throttle the switch should be =on, and at 1/2 throttle= open.You can check this with a multimeter.....or if you don't know how to ..go to the A.S.S,with your specific request for the same.
            When Was The Last Time,You Did Something For The First Time.

            Comment


            • #7
              PSR i think you nailed the problem. I didn't know the existence of such a switch but never the less suspected a problem with timing. So can you elaborate on the exact function of this switch. Is it something like a vacuum advance for cruising.

              Comment


              • #8
                @born2slow: i will get my carb serviced and cleaned thorougly on sunday. also i will tell my mechanic to check ignition timing. this lack of acceleration occurs in 6000 to 7000 RPM. and my exhaust pipe was yellow at the bend. i got it replaced with a new one. i feel my engine overheats a bit. rearding rewinding, i have not done anything to my rotor and not done anything to ignition coil. only lighting and charging coil was rewound with a thicker gauge wire.
                @psr: i will change the reed switch as well, its very cheap.
                i will try all this on sunday. if it doesn't improve next sunday i will change cdi.
                anybody else anymore suggestions.
                help me guys.
                sigpic

                Tyre Sizes _ Spark Plugs

                Headlight Focus _ Fork Oils

                All India xBhp Couple Riders Thread

                Ashtavinayak + Shirdi
                Purandar
                Raigad
                Dapoli
                Aurangabad
                Kaas Plateu & Thoseghar Waterfalls
                Purandar

                Comment


                • #9
                  Why don't you try the reed switch first if its cheap. If the problem is solved it will save you from lot of trouble. The yellowing of the exhaust happens if you are running retarded timing as in your case may be because of the reed switch.

                  Comment


                  • #10
                    wht is the exact function of reed switch. and how it works.
                    sigpic

                    Tyre Sizes _ Spark Plugs

                    Headlight Focus _ Fork Oils

                    All India xBhp Couple Riders Thread

                    Ashtavinayak + Shirdi
                    Purandar
                    Raigad
                    Dapoli
                    Aurangabad
                    Kaas Plateu & Thoseghar Waterfalls
                    Purandar

                    Comment


                    • #11
                      As stated by PSR above and after doing some my own research, apparently the Bajaj guys are running two different ignition timings. One set for less than 1/2 throttle and another for above 1/2 throttle.

                      Comment


                      • #12
                        ok so reed switch is basically a sensor to tell cdi when throttle crosses halfway mark. so dat cdi can change ignition timings.
                        sigpic

                        Tyre Sizes _ Spark Plugs

                        Headlight Focus _ Fork Oils

                        All India xBhp Couple Riders Thread

                        Ashtavinayak + Shirdi
                        Purandar
                        Raigad
                        Dapoli
                        Aurangabad
                        Kaas Plateu & Thoseghar Waterfalls
                        Purandar

                        Comment


                        • #13
                          Originally posted by born2slow View Post
                          As stated by PSR above and after doing some my own research, apparently the Bajaj guys are running two different ignition timings. One set for less than 1/2 throttle and another for above 1/2 throttle.
                          Yes congrats to you on your persistent spirit.The CDI of yester years varied ignition timing according to RPM by sensing pulses of the rpm through the ignition coil on stator (KB100) or through a separate sensing coil on the stator (RX100).The RX 100 of course did not have ignition advance like the KB100 and is the reason for its poor mileage.
                          In the Pulsar there is a pickup coil to give a steady ignition timing and there is a circuit to advance it BUILT INSIDE THE CDI.This circuit is actuated by the reed switch mounted on the carburetor.The magnet on the throttle actuation mechanism either makes the reed switch "on" or "off" and hence the ignition timing advance. You can check it with a multimeter for on or off state depending on throttle position.The reed switch is made of glass,and accidents,or severe jolt near the carburetor is likely to break it.
                          If the pulsar CDI is designed to have continuously variable ignition timing you will get better mileage....or reposition the reed switch or magnet to actuate the switch earlier,then also the mileage will improve.
                          When Was The Last Time,You Did Something For The First Time.

                          Comment


                          • #14
                            Thanks PSR always happy to learn something new. I went through the Bajajusa site where they have this reed switch fitted on their Bajaj chetak imports. Acording to them the less than half throttle setting varies the timing from 16 to 30 deg BTDC and above half throttle the timing is constant 16 deg BTDC. A little too retarded timing in my opnion but may be differnt for the new pulsars. So these guys in US are removing the reed switch and shorting the terminals permently (16 - and that is giving them better power as they have better fuel so they can deal with a bit more advance. So our friends 150 here is behaving kind of strange. Do you have an explanation for its behavior.
                            Also do you have the details for the pulsar timings as i could not find it.
                            Little off topic but extra knowledge never hurts.

                            Comment


                            • #15
                              This problem seems more related to the spark plugs and its firing circuit than the fuelling system. Check the Reed switch, CDi unit and the connections to the capacitors under the tank and the connectors to the spark plugs. As far as how much I know about pulsars [I too have a 180UG3] I am sure the problem lies there. But you can double check the carb and the fuel lines just to make sure.

                              Comment

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