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...odd exhaust smell...

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by phongus, Nov 15, 2011.

  1. Hello everyone

    My Across has come up with a little issue...which I hope would be an easy fix. I have been riding it continuously as a commuter and I have noticed a change in exhaust smell in the yesterday...I thought it was just the air around me but unfortunately that isn't the case when I started it up this morning.

    The exhaust smell used to be the typical exhaust smell...sometimes with unburnt fuel in the mix after some high revving. However this morning, I had the same wiff of weird air as I did all of yesterday after turning the bike on. It is similar to used differential oil used in cars.

    Anyone got any ideas of what it might be?

    Bike is a 1995 Suzuki Across. Oil was changed about 3000kms ago with new filter and air filter was air blown clean. Oil in air box was drained, coolant looks good and there doesn't seem to be any oil usage. To be honest, not sure when the last time plugs were changed but it was earlier this year, lets say March.

    Could the plugs be at fault?

  2. If it smells like diff oil, that suggests sulphur to me. The only place your bike will get sulphur to burn is from additives in its engine oil. Has anything happened lately that might have resulted in more oil than usual getting into the airbox?

    The other alternative is engine wear (rings or valve guides) but I wouldn't expect that to come on suddenly. Blocked breather causing positive pressure in the crankcase and forcing oil past rings or valves perhaps? As a first move I'd check all the breather hoses for kinks and general condition, including pulling them off and blowing through.
  3. Did you fill up?

    Some petrol is distilled from sour crude and can produce a sulphur smell. When Woolworths first started selling petrol they were getting it from PD Van Omeron, who were getting it out of SE Asia. There were putrid smelling cars all round the place.

    I still smell it occasionally, so some is still making it onto the market, but I'm not sure how. Maybe 7/11?
  4. Gotta say, my across's exhaust started smelling a bit funny just before i sold it. An acrid, sort of oily smell, like you say. Smelt like the oil was burning or combustion not completed, but the oil never actually went down and there was no smoke.

    Maybe it's an old across thing?
  5. Thanks for the reply everyone.

    I haven't checked the air box since the last time I opened it up, however I did drain the oil out of the air box this morning thinking it might be the problem, but after a 50km ride to work, it still had a strong smell when I parked. So I assume the air box is not to blame (unless my filter is soaked in oil :?)

    The bike has been used like I normally would, haven't changed anything besides the oil change 3000km ago and the smell only came on suddenly yesterday. I will have a look at all the hoses when I get the chance...this smell is not changing the performance of the bike from what I can tell.

    I fill up once a day (100km a day ride...180km to a full tank) so to be honest, not sure if the smell was from petrol or anything else. I fill up pretty much the same place, however yesterday I did fill up at a BP which I haven't gone to in a while, but I don't remember it giving bad smells before. See how I go when I fill up at another station.

    It isn't so much acrid, more like lingering thick diff oil, which can be pretty nasty (especially burnt old ones in Ford diffs...god damn). I also thought it might be oil in the combustion chambers...but the bike isn't blowing any smoke, which is odd.

    I will have a geezer at the hoses and maybe pull the plugs out (which are a pain in the arse) and see what happens from there.

    If anyone else has suggestions, please let me know :)

  6. Ibast's post does remind me of one other thought I had. Rather than being in the fuel as a result of the distillation process, is there a possibility that the storage tanks at the servo had been contaminated with diesel? That might give you the same effect.

    Maybe run the tank dry and then fill up at a servo you know to be "clean" to see what effect that has before pulling stuff apart to check breathers.
  7. Meanwhile try this:
  8. From memory, the petrol station I last went to doesn't have a diesel bowser, but then again I never look because I don't need it. Filling up after work (nearly empty) and see how that goes on the way home :). Cheers.

    I can't smell it when I'm riding, only when I stop and the fumes from the exhaust waft into my nose. I feel sorry for the people behind me though...
  9. You can get batches of bad fuel. I have to lift the tank and clean out the filter / pick up screen on my 14, because of what I think is snot in the fuel. Not impressed.

    "I haven't checked the air box since the last time I opened it up, however I did drain the oil out of the air box this morning thinking it might be the problem, but after a 50km ride to work, it still had a strong smell when I parked. So I assume the air box is not to blame (unless my filter is soaked in oil )"

    How much oil did you have to drain out? It is possible the air-filter is full of oil and needs to be replaced, but I think you would notice. I mean, if the paper filter was saturated in black sticky engine oil, you'd see it.

    How and why is engine oil getting into the airbox? Did the bike fall over? Or, is positive crank case pressure forcing it up through the crankcase breather?

    Having a look at the plugs might tell you something. If one of them looks black and furry and the others look clean or grey, then you've found which cylinder is affected. But if the bike is running normally and sounds even and smooth, then I don't think you're likely to see much on the plugs.

    I haven't had it happen to me, but I've heard stories of a thing called a PCV valve getting clogged up or jammed or something, which can lead to a sudden sharp increase in crankcase pressure and oil being forced out. It's a thing I associate with cars, not bikes, but it would explain things.

    When you drain and clean the airbox, there's probably oil still sticking to the sides of the inlet ports and the inlet valve. Over time one would imagine this will dissolve in the passing fuel mixture, but I know that on cars it sometimes doesn't, and you need to get into the ports with some carby cleaner and a paddlepop stick or something, and clean the gunk off.

    Would you notice if the bike were smoking a little? What about if there was no smoke on a constant throttle, a wisp on over-run, none at idle, but a puff of smoke when the light goes green and you start to move off? A broken valve guide seal on a car will do this. I've never known it to happen to a bike but engines is engines, so I guess it could.

    I guess when a piston ring (compression or oil-scr@per) sticks, it has to start some time. ... I think that's unlikely, though. With any mechanical question, start looking at the simple and cheap possibilities first, and move toward the more drastic and expensive ones only when the simple ones have been eliminated.
  10. Thank you kneedragon.

    In regards to the air box, there wasn't much at all...maybe 10mL if that. Dropped it on the drive way and just wiped it off with a rag. So I don't think the air filter is oiled up.

    Bike hasn't fallen over or anything, so I'm not sure why there is oil in the air box...I will have to have a look at the possibility of positive pressure pushing oil back out and I'm pretty sure the Across didn't have a PCV...but I'll suss it out. My car had a PCV issue and dumped a fair bit of oil in the intake chambers...maybe something similar.

    In the mornings, when I start it up, there doesn't seem to be any smoke. Rev it out to say 13000RPM (15500RPM redline) it would smoke a little. I have found a bit of oil stain on my wheelie bins though (when I start the bike up in the morning, the wheelie bins are behind it)...however I'm not sure if that is due to my road bike or my track bike (either way, it's bad).

    Looks like Sunday will be a busy day for me.

  11. Engines often throw a few drops of water out the back on start-up, which has carbon deposits and crap in it. Generally it isn't oil, but it looks like oil. 99% it's not something to be concerned about.

    I wouldn't go revving it to almost redline when it's cold, but if it gets oily and smoky at high revs once it's at or near normal operating temp, that isn't a good thing. With a 15k5 redline, I'd look at 5 ~ 8 for warm-up. (Idling doesn't do them any favours when they're cold either.)
  12. Yeah I don't rev it out when it's cold, only when it has warmed up and if I ride it cold, I ride between 7-9k RPM. Honestly, never noticed if it smokes when I take off at the lights though...should look in my rear view to see if I leave cars in smokes.
  13. A quick update.

    I filled up at Mobile this time...the last time was at BP and the one before that was at a Caltex (The servo was closed today for either maintenance or upgrade :?). There was maybe 2L of fuel left in the tank and filled it up to the brim. After I filled it I got the same waft of odd smell. I decided to give the fuel tank a sniff and to my surprise, it did have a similar smell to the exhaust smell but not as bad...it still had a fuel smell to it.

    So for now I will blame it on the fuel and will try a Shell petrol station after next fill up (probably tomorrow arvo) and have a sniff of the fuel to see how it smells.

    Usually I like the smell of petrol, but this petrol didn't smell so inviting...maybe that's why the barrel was so much cheaper.
  14. Thought I'd update after a week of riding...

    Well since my last update, I filled up 4 times. Until my last fill up (4th one) the smell was still there using different petrol stations but it wasn't as bad. Filled up last night on my way home running pretty much on fumes at Shell (outbound Westgate). No smell when I got home and no smell when I rocked up to work. I gave the fuel tank a sniff and it smelled like normal petrol, none of the ugly odour of sulphur.

    So in conclusion, the fuel was crap all of last week from pretty much all petrol stations (including Shell). New fuel delivered this week must be of better quality.

    No more stench :D.