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RS 125 am I riding it wrong?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Paulie, Sep 29, 2007.

  1. Hey guys!

    Just picked up a 2nd hand Aprilia rs125. Doesnt blow any smoke and sounds really healthy, she runs and sounds great higher in the rev range but when I take off at lights she takes off REALLLY slow, like I really have to ride the clutch hard and give it a massive fistfull of throttle an even then she is pretty slow in revving up...she only has about 10,000kms on the clock

    I'm hoping she just needs a carbie clean?? Also to all you 2 stroke guru's... I cant just throw that carbie cleaner into the petrol or it will damage the engibe wont it??

    Sorry if I sound dumb, (first 2 stroke) and hoping I didnt buy a cheap lemon (or an expensive one)

    Any ideas would be greatly appreciated

    thanks i advance
  2. I'm no expert either, but my guess would be carbies running too rich - your sparkplugs are prolly in need of a clean or replace too - I think they'd be black and sotty if I'm right?

    Maytbe one of the more mechanically inclined netriders could confirm or deny.
  3. Depending on the gearing, there is a good chance that you do indeed have to rev the tits off it, ride the clutch, and probably give it a bit of a push with your feet to get off the line. Get a mechanic or a mate who's familiar with RS125's to go for a quick spin and put your worries to rest.
  4. Does it accelerate well once in the power band, from around 7 to 10,500 rpm?

    If so, there is nothing really wrong with it, I would say. You just have to get used to high performance 2 strokes. Once you master the art of slipping the clutch gradually, and gently feeding in the power, you should manage smooth takeoffs.

    You will have to keep the engine in this range to get any performance at all in the top 3, maybe even 4 gears.

    Welcome to the real (2 stroke) world!


    Trevor G

    PS Isn't it fun once it gets going, though!!
  5. I'd do a plug-chop and check just in case. If they're black and 'gunky' then you may need to get the fueling system checked. On the other hand a quick check would be just to throw a brand-new set of plugs in it and see what difference that makes. (A flat-out blast for 20 minutes or so will also tell you a lot, but may shred your license, so, perhaps just do the plugs :LOL:)

    But either way, welcome to the mad world of the two-banger, and keep a couple of spare plugs (at least) under the seat with your plug spanner :wink:.
  6. Welcome to the world of 125cc two stroke bikes. If the engine is running smoothly and not blowing any mass vapours then there is nothing wrong with your bike.
    Unlike the mechanical advise that many like to give (like medico giving chemo treatment for a cold!) you will find that these bike have absolutely no power at all, except in thier power band range.

    To take off you will need to fan the clutch and build up forward momentum.

    That is why these bikes are the worst for learners, as you are really riding a small scale track bike, who is designed to sit on level ground and stay in a particular RPM margin.

    As soon as you deviate off this optimum RPM setting, the bike has like no power to deliver to the drive train.

    You will get used to this. Just slowley let out clutch and apply incrementally more and more rev's until you build up forward motion.

    Remember you have a bike that will poroduce the power of a two fidy (but only once you hit the power band) but the torque is about one quarter that of a two fifdy.
  7. So its normal for it to stall out if you try to take off like on a normal bike? I'm just worried that I bought a lemon cause it was so cheap, but once it gets going it goes really well.... just a bit worried about taking off... if I turn up the idle will that damage the piston/barrels at all?? cause it idles really low aswelll
  8. Why do you think it is idling low?

    It should idle at around 11-1200 rpm, I would guess. The Cagiva Mito is set for 1000 rpm idle, the NSR150 is 1300 rpm. The important thing is that a steady idle reduces stalling (without load, not when trying to take off).

    Don't set it too fast because that could inhibit cold weather starting.

    It will not run/take off like a "normal" bike. These little zippers have nothing below 7,000 rpm, so you need to gently/gradually slip the clutch while you slowly increase engine revs. You will get used to it. :)

    I use about 3,000 rpm on the NSR 150 and can be really smooth after several months' practise! You might find you need 4500rpm or more at first - just don't give it a big handful

    Give it too much throttle at take-off and you could find yourself launched into a car or a fence... ;-)

    Cheers, and have fun

    Trevor G

    PS "Feather" the clutch - let it out a bit, if the revs drop too quickly pull the clutch in just a fraction, then let it out again as the revs rise. It's a case of balancing throttle against clutch when you want a smooth takeoff.

    PPS DON'T set it to idle faster to help you get a good start - that will cause other problems. Just practise until you get it right!
  9. hmm.. thanks guys

    I went and fired her up this arvo and she almost killed me with the smoke there was SOOOOO much smoke..... I know they blow smoke when cold but this thing blew HEAPS... though once shes warmed up (above 70 degrees on the reader) she doesnt seem to blow much/any smoke... once again.. does this sound about right?

    Sorry for all the newbie questions, I have owned a V twin and a 4 cyclinder this is my first stroker and I always respect the advice from netrider
  10. sounds right. 70.c is a little hot, should be running around 60-65. Depending on the oil ur using, the bike will smoke a bit cold and gradually smoke less as the temp increases.

    I agree with the others that it maybe fueling. Have u checked your powervalve, and that its opening correctly, because if its not it will seriously affect any power belvow 8000rpm.

    Might be in need of a top end rebuild.
  11. Top end rebuild... please dont say that!

    Hopefully I just need to learn how to ride it properly, also I think its been properly run for a while...rego expired a few months ago... is it easy to clean the carbie on these? I cant find an online manual for the rs125?
  12. Top end rebuild on that would be cheap as.... But I really dont think you need it. most likely you're experiencing the consequences most learners have from riding a revvy two stroke.

    All your symptoms of the bike sound like business as normal and it sounds like you've got a sweet little RS125 there.

    Two strokes will foul up if not ridden in or near the maximum efficiency (read power band) for an extended period. The whole combustion cycle revolves around turbulent interference of gases - outside of a carefully tuned band they are horrendously inefficient.

    Make sure you do some of your riding in that rev range when it's safe to do so (eg not in heavy traffic) and then it should stay much cleaner and crisper.
  13. Hey, I ride a cagiva mito. Here's my advice:

    For a slowish start, prop the revs up to 5k RPM and feather out the clutch. You will be well and truly moving by the time the clutch is fully engaged. It's very much about riding the clutch. Try holding the clutch half engaged and feather the throttle instead. Unlike 4T's, it's a very intimate relationship between clutch and throttle.

    0-5k RPMs are an absolute joke and you shouldn't really be in there except waiting at the lights, I cruise around 7k rpm or a bit below, in case I need a sudden bit of power.
  14. Some more advice:

    Try not to leave it idling for a long time. I get anxious at overly long traffic light delays and I'll rev it slightly.

    Leave the choke on during cold starts for a little as possible. 30secs to 1 min should be enough to get it idling without stalling. Much longer and the plug will foul and it will stall and not start till you change it. Shell V-power sucks balls for this. I only use BP ultimate... I can feel the difference between other fuels.

    It'll smoke the most when cool (<60 oC). Even more when the choke is on. At operating temp (>60 oC) it shouldn't be smoking, maybe a bit of a haze. Don't boot it when cold unless you want a cold-seize.

    It'll smoke more when idling and when you boot it after a period of idling. After idling for a while it will feel boggy, I suspect because of carbon deposits everywhere.

    Moral of the story, warm it properly and ride in the powerband 7k - 11k most of the time.
  15. The carb is easy to clean, but why bother?

    What do you think is in there? The bike is performing normally, and if you haven't done that sort of job before you stand the chance of creating a problem that does not exist. ;-)

    The smoke when cold is due to:

    1) Using the choke

    2) Not enough revs or load to clean out the extra fuel/oil mix from using the choke.

    If you haven't had a 2 stroke before you will find that:

    3) Just revving the bike without any load will not clear the smoke

    4) When you accelerate it won't go over, say, 5 or 6,000 rpm in first, even if you hold it flat for 10 seconds

    5) As you change into a higher gear it will rev out further and further. Sometimes just changing into second and accelerating again will clear the muck and it might wind out to 8 or 9,000.

    6) Don't run it hard until the engine has warmed up. Less than half throttle and just into the powerband for the first km or two.

    7) Get the choke off as soon as possible. Don't leave it idling with the choke on - ride it (gently) as soon as possible or leave it running just above idle until it has warmed a little.

    All the best and enjoy :)

    Trevor G