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Engine Oil Question

Discussion in 'Technical and Troubleshooting Torque' started by puppywarewolf, Nov 27, 2004.

  1. Hi guys,

    Just a question regarding my baby ZZR.

    I am finding that I am topping up oil a fair bit lately... Probably every 1000-1500 km's. Roughly that is could be more could be less....

    Anyway, the bike isn't blowing black smoke or anything and goes very well from what my unmechanically minded brain sees. There are no leaks. It just seems that the engine is slowly burning it away.

    Would this be a normal occurance for bikes that age.

    It is a ZZR250 1992 Model, grey import.

    Thanking you all in advance for any assistance.

    Cheers



    THE PUP.
     
  2. How many K's on the clock. How much oil are you putting in.

    If its not much it's OK.
     
  3. I had the same bike (same year too) with over 40000kms and I never needed to top up oil. but if it's only a little, shouldnt be a prob

    I'd try the test where u get someone to ride behind u and u open the throttle at say 7000rpm, cut it, then open it again (the person watches for black smoke)
     
  4. What is the quality of oil you have in there now? (ie. when was it last changed?) It could be worth draining it all and seeing if you have any water or other contaminant mixed in with. If water, then this may suggest you have a leak somewhere.
     
  5. I think I read something about this.

    The ZZR250 is a 360deg parallel twin. Which means that both pistons rise and fall at the same time.

    The result is that when they wear a bit they pressure in the case tends to blow oil out of the crank case breather.

    This is probably located in the rocker cover and goes to a hose. From there is may be to air, or under the bike, or the air intake.

    There is not much you can do about it, but:

    1. it may be worse at high oil level. Maybe try running oil at the lower mark and see if it uses it as quick.

    2. If the hose goes to the breather, disconect it and run it to a bottle. This will tell you how much oil it is losing though the breather. It will also make the intake air cleaner and thus make the bike run better. If you don't do this it may start to foul plugs. Make sure you block the air box hole.

    Let us know how you go
     
  6. Firstly, ibast sorry but im pretty sure you've got it wrong about the zzr/gpx250 motor being a 360' twin.

    I used to have a bike based one of these engines (service manual is at home, not work) but from looking at at the part diagram here and talking to mates, im pretty sure it's a 180' twin. I'm pretty sure of this because a CB250 is a 360' twin and starts rattling your teeth out at anything about 7krpm and the gpx/zzr250 motors are just starting to really pull at that point and redline at 12-14krpm and a much higher top end. :)


    Now back onto the rest of troubleshooting :):
    These motors can eat a bit of oil (100-200ml every thou kms or so) if you keep it in the top end of the rev range for a long time (syd-p.i. did it for me) and don't change the oil regularly, this is a combination of perhaps a bit of blowby past the rings with air being recirculated from the crank into the airbox. Check the airbox for oil first, this normally has some in there, but it's usually not very much, perhaps a tablespoon of oil at the most.

    If this doesn't give a satisfactory answer as to wtf is happening then read on. There are a couple of things to check on a motor, i'll explain each one & the why's behind them (as best i understand them that is). The first test just confirms if you do indeed have an engine that likes eating oil, the second and third test helps confirm where the problem is likely to be.

    First: (easier method, no taking stuff apart)
    Get two peices of folded up kitchen paper toweling and once the bike has been totally warmed up and been run around for about 10 mins to get any condensation out of the exhaust, get the bike into neutral and have someone lightly hold the towels over both exhausts at the same time.

    Then give it a very quick blat at med-high revs (8-9k) for a second or three. You *might* see tiny specks of carbon from the exhaust, these are little chunks of black stuff, this is normal as your giving the motor a bit of a run. But the thing to look out for is oil specks, which are pretty easy to see on the highly bleached towling as a light grey stain, sometimes with a black centre.

    It's normal to see a very very very tiny amount of oil, perhaps one or two 1mm spots if you are unlucky. Any more than this is an indication of oil possibly leaking somewhere.

    second (and more involved & reliable)
    Get the fairings and tank off enough to take the plugs out and check, if they are a lightish grey then they are running perfectly. If they are dark brown to a bit black and sooty then they are running a bit rich, if they are a bit gooey and black then you've definately got an oil leak somewhere.

    If the bike has clean plugs yet is getting big splotches of black on the paper, then it's more than likely either an oil leak (which you've already said isn't happening) or your valvestem seals(s) for one or more of your exhausts is kaput.

    If the plugs are black as well as getting the splotches, then either the inlet valvestem seal(s) is/are shot, or there is wear on your rings & perhaps bore.

    third: Final check, needs equipment
    A compression test is the easiest way to check if its the valvestem seals or the rings, if its the rings you will get a lousy compression ratio. If the rings are in top condition you will get 160-180 psi (12:1 comp ratio x atmospheric pressure(14.7psi) =176psi if you were curious). if they have been a little worn you might see it as low as 120psi, if its anything lower, your rings are shot totally.

    If the test indicates above 130psi then your rings are in a fair condition and may be only slightly contributing to the problem and its most likely a leaky stem seal. In any case if you're getting any of the above, you are quite possibly going to need to get the engine worked on to fix this up.

    As an indication, to have all my valve stem seals replaced, new rings, a rehone of the bore & a new timing chain set me back about $900 on my EL250 a year or two ago. if its just a valvestem seal then the head still has to come off, but it's only a little less work. ;-). in any case if the compression test gives under 130 then unless you want to hold off on the spending (it'll go for ages without getting it fixed before anything comes remotely close to breaking, just as long as you keep it in fresh oil) then a top end rebuild would be recommended.

    Sorry about going on and on and hopefully i havent lost you, and i'm not too wildly inaccurate with what i've posted. But i thought i'd try and explain this clearly, given that i was in the same situation as yourself a little while ago.

    [edit: sorry, i initially thought it was mouth that said that about being a 360' twin!!]
     
  7. A question on oils, what brand of oil is best to use. What brands should I be avoiding. My '95 zzr250 manual says I should use grade SE, SF or SG class with viscosity SAE 10W40, 10W50, 20W40 or 20W50. Which grade/class should I use? (it says I can use any, but maybe there's a 'best' option?)
     
  8. is the oil is getting changed every 3-6k km's?
    And with good quality oil. once oil starts to break down
    it burns easier thus requiring top ups!!
     
  9. Wrong!
    Black smoke is an indication of a petrol dump, on full throttle, not burning oil.
    Burning oil is blue/grey smoke.
    black smoke will occur if you snap open the throttle quickly resulting in all the fuel not being burnt completely hence the black smoke.
     
  10. If you do a lot of city commuting then take it for a highway run continuosly for a while you will find you will lose a bit of oil.
    This is because some water condensation will occur if the oil is getting on.
    A long highway run will burn off all the excess moisture resulting in a "real" oil level.
    This is when you should top it up then go on another run.
    You may find that you won't lose as much oil.
    City commuting tends to give a false impression when checking the oil levels because of all the condensation build up
    Also make sure your valves are adjusted to spec.
     
  11. RIGHT!!!

    black also could indicate a blocked aircleaner.

    JJ