Power Loss



  • Hey guys -

    My bike seems to be a bit down on power, so I am just wondering what the main causes are and where I should be looking, based on your experiences???

    Thanks



  • First port of call would be to change the spark plug. Not too sure what else without details, does it not pick up as well etc?



  • @Burridge Yeah she runs fine and pulls well, just not as hard as she used too. I noticed that my top speed was less than before and there is less of an initial jolt when accelerating hard. I did swap the plug from a regular to an Iridium one about 6 weeks ago and she flew after that, but could it be that the plug has backed off or maybe deteriorated already?I did notice some carbon build up on her and have cleaned her up a couple of times. The only other mods I have done is to remove the air bottle and fit a Pipercross air filter, would those mods decrease the mid/top end speeds? Apart from that I've not changed a thing.

    The only other thing I can think of is I fitted new tyres and the front is slightly wider, with a slightly bigger circumference. So that may be offsetting the speedo and giving a false reading???



  • @CYBER-NINJA Sounds like it's slightly lean, the Pipecross Airfilter increases Airflow and leaned the mixture a touch on mine.

    I ran a 260 Main Jet, Pilot 27.5
    For Midrange settings, start with adjusting the Needle/position, you'll want to add fuel to gain the correct Fuel to Air Mixture.

    Humidity at the moment and Air density will also effect results,



  • Humidity will cause a loss in power. The added water vapor content in the air hinders the propagation of the combustion flame.


  • Global Moderator

    I'm also noticing a little bit of power loss in the top end of the rev range but am not worried as I have always found that power on 2 stroke bikes seem to fluctuate every now and again.. Definitely could be the weather.



  • @Calum said in Power Loss:

    Humidity will cause a loss in power. The added water vapor content in the air hinders the propagation of the combustion flame.

    @MIGHTYMAN said in Power Loss:

    I'm also noticing a little bit of power loss in the top end of the rev range but am not worried as I have always found that power on 2 stroke bikes seem to fluctuate every now and again.. Definitely could be the weather.

    Would the high humidity cause my top end speed to drop by 12mph though???



  • AHh I wasn't saying that was your problem. I was just stating humidity can cause power loss. 12mph seems excessive.



  • @Calum The heat and humidity may be a factor, I'm gonna spray the exhaust this weekend so I'll check that the PV is set to open correctly, as per your vid. I have also been doing some research and found your comments on this thread to be very interesting Calum;

    http://www.dt125r.co.uk/topic/95/normal-spark-plug-vs-iridium-ie-denso-iw27-or-ngk-br9es

    I suspect that the plug has deteriorated and will order a new one so that I have something to compare it against. I found this dude on ebay who sells em for £7.57 delivered, so it's a cheap means to test the plug out!!! ;O)



  • I reinstalled the air bottle on the carb outlet and my bikes back to warp speed again! :O)

    I'm not sure exactly how it all works as it's only a boot shaped bottle, something to do with air pressure and vacuums I guess? Which makes the carb open up a bit more to increase air flow, or something along those lines? Anyways full power restored so I'm a happy tank hugger now!!! LOL

    Thanks everyone for your help. ;O)


  • Global Moderator

    Good to hear a simple fix!


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