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Aprilia RS125 White smoke and "the drip"

Discussion in 'Technical and Troubleshooting Torque' started by yumenuu, Aug 10, 2015.

  1. Just looking for some advice to help, I know it's not guaranteed, hone in on the issue with my bike.

    It's started to smoke, white smoke, with increases with acceleration. Boggy to accelerate from 8k rpm until about 9k. Started to get a couple of oil droplets underneath the bike now when it's parked.

    Here's the extras it has, as told to me when I bought it:

    1999 RS 125

    -34MM CARBY

    Any info would be greatly appreciated. Thanks.
  2. Here's my take on it, having owned two-stroke motocrossers in the past:

    It's a two stroke. They smoke.
    If you're getting more smoke than you used to, what have you changed? Changed oil brands?
    Are you using premix? Are you mixing at a lower ratio?
    Does the bike have automatic mix? Is the automatic oiler working correctly? If it's vaccum-operated, an over-oiled or excessively dirty air filter can cause it to suck more oil, resulting in a richer mix.

    A clogged/over-oiled air filter can also cause a premix bike to suck more fuel, making it rich and smoky as well...

    It's a two stroke. They (mostly) have a really narrow powerband.
    See above points as well, a richer mix can cause low-down bogging, if you weren't getting this before.

    It's a two stroke.
    If it's running rich/too much oil, you may have oil-logged the packing in the silencer. This will then drip out wherever it can when the bike sits...
    • Agree Agree x 1
    • Informative Informative x 1
  3. White smoke is generally water (black smoke too much fuel, blue smoke oil). Is the bike water cooled? It might have a leaking head gasket which could explain most of your symptoms.
    I had a KR250 that had boggy acceleration that was boggy below 8k, it can be due to out of balance carbs/throttle bodies. After careful balancing it would roll on from 7k in top. Is it a single or a twin?
    Oil on the ground under the bike can be from an over oiled chain, a leak, or the afore-mentioned choked silencer packing. Knowing if it's gear-case oil or two-stroke oil might help.
  4. Some more points I had forgotten, Dark AngelDark Angel

    Water would also make the exhaust gases feel "damp".

    I'm pretty sure that the little RS125's are singles, so that would rule out carb sync.
  5. Rs125 are all water cooled - oil injected
  6. Single cylinder
  7. If its water cooled and blowing white smoke, that usually means its time for a new head gasket. You can check by leaving the bike stand over night. The next morning remove the spark plug and look down the plug hole with a torch, you will probably see coolant on or around the pistion.
    • Informative Informative x 1
  8. If it's water (steam) it'll evaporate as it drifts away.
    Large amounts of unburnt oil can look white in certain light conditions. The best way to tell the difference is, if it hangs in the air or doesn't quickly disappear as it blows away, it's oil.
    Of course, a blown head gasket might cause both water and oil to escape...
  9. If it is a blown head gasket it's very cheap to fix and do it yourself .
    It's piss easy to do and will take only a few minutes to change it out and fit new one.
  10. you don't tell us how many kms' you've done or when it was last maintained......these things are fairly simple but high maintenance.

    maintenance schedule attached, note the following,
    - 4k kms clean or replace the plug,
    - service life of the piston. rings and barrel
    - exhaust ( power 'rave' ) valve maintenance requirement.

    All not hard to do.

    engine service manual can be found online, look for "Aprilia125, Rotax 122 Manual Reparatie.pdf"

    rs125 maint sched.
  11. Hey, thanks everyone for all the overwhelming responses. First time here, but I've been on auto forums before (especially cars) and this is the first time I've gotten this much help right off the bat.

    Yes, sorry I didn't post more maintenance info on it. I've honestly only had it for about a month or so, so I didn't really have any maintenance to report on it before. It's sitting at 20k now, and the previous owner claims that the engine was rebuilt 2k ago. I've done one of those k's.

    It is something that I HAVE noticed since changing oils. Using "Motul 2t 710 (full syn)" now. There was alot one before that but I couldn't find it so I just bought the motul on shop recommendation. I first noticed that it was going through the oil very quickly (it's automatically mixed), and I was going through 2ish liters compared to the 1 liter from the brand before (don't remember the name). I started noticing a bit of white smoke letting it warm up later but just figured that it was normal (typical 2 stroke), and that perhaps there was more of it because it was winter.

    I only noticed that it was making alot of smoke when I got pulled over and questioned by the cops about it. I've since noticed that if I rev it that it basically creates a mini smoke screen behind me. It plumes out, just looking at it standing next to it as I rev it. It was never like that before, it would smoke a bit, but not like this.

    So I've let it sit for a week now, there's a hand sized oil puddle/ print underneath it. I started it up, rev'd it, and put my hand behind the exhaust. My hand was dry, no moisture, no oily gleen.

    I have a haynes manual for the bike, and proper tools, just thought I try to see what the possible choices are so I can see which chapters to pick. Was a bit uncertain too since the bike has some mods/ upgrades.
  12. My KR crapped out the crankshaft oil seals not long after I got it. I knew something was very wrong pretty quick though as it STUNK of gear oil, which was being sucked into the pre-compression chamber and burnt. It might be worth making sure the exhaust doesn't smell like the gearbox oil.
  13. I've owned 2S dirties and an RGV roadie. Aprilia used the 250 engine from the RGV in their RS250 so here's my take.
    They had an automatic oil pump system which worked well for a while but where temperamental in the long term. Some people revert back to pre-mixing to ensure the best mix.
    If you're getting over mixing then you will def see it in several places. The first being the consumption. The second being out the exhaust via "plumes" of thick white smoke that lingers. And third you'll see it form as "Spoog" (excess oil deposits) around the exhaust header gasket or joins in the pipe as it will find its way out of the engine any way possible. Grab a torch and find where the oil is dripping from.
    Have you checked the condition of the plugs as they would be the first thing I'd be checking. Odds are they are fouled which may be what is causing your bogging mid rang.

    Sometimes the oil pump develop slack in the cable which causes over mixing so one way to check is as follows:
    -remove pump cover behind front sprocket.
    -there is a loose grey wire with an insulated female bullet terminal near to the battery negative, with main ignition and engine run switch in the on positions connect the grey wire to the battery negative, the PV servo will open to the setting position, switch off engine run switch. Adjust oil pump cable to have zero play.

    It may (doubtful) also be the change in oil brands so a quick way of testing this is to change brands. Also jump on RGV Aviation | Taking the Hassle Out of Ownership | RGV Aviation Limited - Maintenance, servicing, avionics, repair and parts for aircraft. Including Cirrus, Cessna, Piper, Diamond and others as there are some good tips.

    Do let us know how you get on

  14. I'd start looking at 'leaking' valve stem seals = white smoke.

    Easy to replace, just becareful installing them, as you only get one go.... or buy a couple of spares, just in case.
  15. Not sure about valve stem seals on a 2-stroke. Things are changing all the time though so I could be wrong.
    • Funny Funny x 1
  16. I'll take the fairings and bits off this weekend and have a look at it (won't be free until then), with pics to follow. I've been too busy the past week, and broke, to do anything about it. What does gear oil smell like?
  17. 2 strokes don't have valve stem seals.!
    • Winner Winner x 1
  18. Smell your gearbox oil and you will find out.
  19. #19 dobbo, Aug 11, 2015
    Last edited: Aug 11, 2015
    This particular model does!
    Here is the microfiche link to the page, check out 'item 6, part number AP0230810

    I had similar issues with my DR regarding the white smoke (I know the DR is not a 2-stroke), however, the 1999 RS 125 does have valve Valve stem seals within the Exhaust Valve set up.
    Looks even easier to replace than conventional valve set ups.

    After googling the part no:
    Genuine Aprilia Part Cylinder Valve Stem Seal AP0230810 Each ETX Pegaso RS | eBay
  20. Different function.

    4 stroke valve stem seals prevent engine oil in the head seeping down the valve stem into the intake/exhaust ports.

    The mentioned valve stem seal for the RS125 seems to prevent exhaust gases escaping to atmosphere via the powervalve actuator.
    • Agree Agree x 1