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my rs 125 seems slow + speedo problem ?

Discussion in 'Technical and Troubleshooting Torque' started by Aprilia, Jan 4, 2012.

  1. after riding a friends aprilia rs 125 and then comparing it to mine, it seems im losing alot of power and that my speed sensor is playing up

    trying to fully d-restrict my bike with the catalysis removed from the exhaust chamber and the cdi drilled, i can only clock out a HUGE number of 124kmp/h
    straight after jumping onto the other rs 125 which is completely stock was clocking out at 135kmp/h and still climbing
    i was wondering if anyone could point me in the right direction, would it be the carbie being blocked ? spark plugs ?

    my speedo also from time to time play up, going from say 90 to 100 it will jump up to say 114 then 120 then drop back down to 80 then back up to 115 etc,
    is my sensor damaged in anyway and or is the cable starting to go faulty

    i know its not big problems but if its not running 100% the way its suppose to i dont feel right about it haha
  2. is there a sucking sound coming from the engine?

    I lost something like half the engine power before it died out on me.
  3. i dont think so, not to my knowledge
  4. as for the speedo the cable connecting it might be spinning freely........fiddle around the bottom of the speedo guage.
  5. My dead stock '10 RS125 easily accellerates past $1.40, even with my fat arse on it. Are you sure you haven't screwed something up by screwing around with it ?
  6. That's the thing I don't know what the exact problem is, I can't get a proper reading from my speedo from the beginning
    Tomorrow I'm going to try fix the speedo then open up my airbox and my carbie and care if anything is blocking them
  7. A stock 06 I wound out to 150kmh and ran out of straight road. It really depends on how the bike was run in, condition of all small things. After you check the basics like making sure your airbox and carb have been secured properly, check for exhaust leaks, chain lube, alignment and tension, wheels can freely roll, carb settings and so on.

    As for your speedo, make sure the pickup is clean.
  8. I would say after guttin ur cat u need to rejet seems ur.gona re jet I would get a 34mm carb, arrow/ jolly MOTO exhaust.
  9. What ONE said. Especially on the smaller bike, being even slightly out of tune will make a noticeable difference.
  10. yea i was comparing it to a friends 08 stock rs 125 and it was 135kmh and still climbing
    as for the pickup is that the speedo sensor ? would you know where it is or what it looks like ?

    i am trying to full power my bike but didnt think that doing those two things would hurt the performance of the bike (without the 34mm carb,rejetting and the exhaust)
  11. maybe you should consider enlisting the help of a professional rather then just ****ing around with your bike. ****ing around always ends in tears.
  12. The magnets are mounted on the rear rotor, sensor just off the swingarm. Have a look there, give them a clean and check the clearance of the sensor to the sender for each item.

    Aus model bikes came full power out of the crate.
  13. I think speedo runs off the front wheel..........check that cable that runs from your cluster to the front wheel, sometimes the top end just spins away and your speedo jumps around.
  14. Have you cleaned out your power valve? While pulling my bike apart for rebuild I noticed it was VERY sticky had some really thick black oil all over it.

    Before the rebuild my bike was doing the same thing, lack of power after 6000 rpm. When I first got it it would pull pretty hard but after a year it was lacking power.
  15. My bro had a lot of problems with his powervalve. Could be that. Made his bike gutless
  16. If it's black and gummed up you're not riding it in the powerband....ride harder :p
  17. im unsure of where the power valve is
    im looking through the manual and cannot find anything about the power valve ? (unless it is the rave unit ?)
    thanks for the help!
  18. Power valve is in the exhaust port...raises and lowers according to the engine revs...usually operated by servo motor ( via cables ) although some 2 stroke MX engines ( KTM ) use a mechanical actuator driven off the crankshaft.

    Definitely, if the power valve is stuck in the low speed position the engine will lack ( midrange to top end ) power. Alternately if the power valve is stuck fully open then the engine will have less midrange pull but a peaky top end, great fun if you can keep it in the powerband, but not so much in traffic....

    eg. RGV 250 PV diagram

    Attached Files:

  19. Lift up the tank and take out the battery and the stuff that surrounds it and I think reposition the coolant.......theres two hex bolts.........simply pull it out and clean it up, make sure to remember how the valve is positioned. It might be gummed up and hard to take out at first, sometimes its better to first run the engine a bit and build up some heat.
  20. What those guys said - when I first got mine on the road after buying it as a wreck it would top out around the 120/130kmh mark.

    My first instinct was to rejet. That did sod all so I went back to stock.

    I then read up and checked the powervalve - it was actually fractured so I took it out all together and machined a blanking plate from 3mm aluminum flatbar to go in its place. This was held in with a homecut gasket and the original hex-head bolts with spring washers. After an initial 500km I tightened it and checked for leaks... it performed flawlessly for another ~10,000km until I sold the bike.

    I did not miss the midrange at all... as there isn't any to start with. Fuel consumption wasn't very good though (mind you I was always up it) so you may want to replace or service rather than remove.

    If you do a search for posts be me and include the terms 'Aprilia RS125' you should encounter a lengthy thread on my RS125 which will have all sorts of info in it.

    Cheers - boingk
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