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Old 25th September 2009, 13:44   #1
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Exclamation Zen exhaust spitting lots of carbon powder at high revs after cold start!!

Yesterday a strange thing happened in my zen.

My zen generally drops water from silencer during cold runs. I have seen water drops not just at first starts but even rest of the day. My zen has done 81K kms. Its a carb one.

Yesterday, during cold start with couple of mins of idling. Then i did some real high revs. To hear the engine sound. I saw carbon/soot power being thrown out from silencer, lots of it!!!

I had my bucket of water some feet away. I saw carbon thrown on that too!

Also after couple of high revs, it gave real black smoke for 2-3 secs!!

When i opened air filter box. I saw very thin film of oil in bottom of air filter chamber. Also the pipe that gets air from engine to air filter compartment had oil film in it. Im not trying to link things here. Let me know if i need to check for something else too.

Power is adequate. Engine is silent. Mileage in city is 11 & highway is 17. Havent noticed engine oil getting reduced.

Im not sure whats going on with my zen...?
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Old 25th September 2009, 13:55   #2
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it may be due to fuel not being burnt up properly/incomplete combustion of the fuel . May be you need to check your air filters coz it might not be letting enough air. Do you notice any sputtering of the engine ?
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Old 25th September 2009, 13:59   #3
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it may be oil leak.. just get it serviced /checked at the earliest before it leads to some major issue..
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Old 25th September 2009, 15:18   #4
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air cleaner i checked, also I blew some dust off.

However, the smoke is black. What might have gone wrong. Something major or minor?

oil leak, can you please elaborate?

Thanks.
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Old 25th September 2009, 15:30   #5
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Your car needs a complete tune up job, thats all. The oil you see is from the valve cover breather system which is connected to the air filter box. Maybe a good idea to cleaning this and check if excess oil is getting in. But am sure its more of high mileage issue.

You just go for full tune up of carbs, valve setting, filter clean up/change, spark plugs and your car will be perfectly aok.

Black soot accumulated over the years get blown off at high revs, also the rust dust which is normal in an old silencer. Once in a while high engine speed driving at lower gear clears up the throat of the car which is know as the italian tune up

Last edited by Jaggu : 25th September 2009 at 15:31.
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Old 25th September 2009, 15:35   #6
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are you sure the engine is not running rich? I am not sure though how the oil will reach the oil filter . Do you notice oil inside the filter, if so that i guess it indicates something major. You might want to get it checked quick.
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Old 25th September 2009, 15:46   #7
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I had this problem a while back on my 95' Zen which has done 1.25lacs. It was due to the high-speed jet getting stuck. Replaced it and did a tune-up. Problem gone.

Last edited by unni.ak : 25th September 2009 at 15:47.
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Old 25th September 2009, 16:03   #8
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Im planning to do a complete service which would include all things said below. Also clean up air filter compartment.

Any chances of gasket or any other fault?

Will keep a tab on oil again getting its way to air filter compartment.

I will keep this thread alive till problem solved.

Also, if any one has any more ideas, please let me know before i take it for service, which may be ard 2nd week of Oct.
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Old 25th September 2009, 16:42   #9
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i doubt its a oil leak. since you said the smoke was black, if the engine was burning oil, the smoke would have blueish color.

most likely a fuel jet problem.

UM
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Old 25th September 2009, 16:48   #10
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Quote:
Originally Posted by Jaggu View Post
Your car needs a complete tune up job, thats all. The oil you see is from the valve cover breather system which is connected to the air filter box. Maybe a good idea to cleaning this and check if excess oil is getting in. But am sure its more of high mileage issue.

You just go for full tune up of carbs, valve setting, filter clean up/change, spark plugs and your car will be perfectly aok.

Black soot accumulated over the years get blown off at high revs, also the rust dust which is normal in an old silencer. Once in a while high engine speed driving at lower gear clears up the throat of the car which is know as the italian tune up
+1 to that, get a tune up done and an exhaust de-carb too. The oil from the breather is nothing to worry about.
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Old 25th September 2009, 16:53   #11
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thanks for these words.

I was worrying abt engine eating oil problem. Hoping not a major issue.

Is it a good thing to high rev engine and let more of these carbon come out? or wait till it is serviced?
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Old 25th September 2009, 17:21   #12
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Quote:
Originally Posted by UniqueMods View Post
i doubt its a oil leak. since you said the smoke was black, if the engine was burning oil, the smoke would have blueish color.

most likely a fuel jet problem.

UM
+1 to this. If the oil is burning you will have bluish color smoke. This is something related to high mileage issue. As the techies has mentioned do a full tuneup and a general service. Ask the mechanic to check the catalyst and the rust condition of the silencer too.
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Old 25th September 2009, 17:48   #13
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Quote:
Originally Posted by athalaga View Post
+1 to that, get a tune up done and an exhaust de-carb too. The oil from the breather is nothing to worry about.
Careful with any kind of decarb, engine decarb can displace carbon and create havoc if you do it with those decarb machines. Best is to dismantle and do a manual clean up, which is overdoing it since your car is running well.

Exhaust also careful since it can dislodge the baffle if they are weak and eventually you will have to replace the system.

I would suggest changing oil to a good Mineral oil like Castrol Magnatec instead and leave it at that.


Quote:
Originally Posted by devrajman View Post
thanks for these words.

I was worrying abt engine eating oil problem. Hoping not a major issue.

Is it a good thing to high rev engine and let more of these carbon come out? or wait till it is serviced?
Unless engine is drinking 200-500 ml oil every 1000 kms its just fine. Also see if your exhaust tip is has wet oil residue (not water), am sure it will not be. It might be dark due to the car running rich thats all.

Ideally finish the job before you go high revving, to avoid any further confusions/complications.
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Old 25th September 2009, 18:24   #14
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While your engine is warmed up and idling, open the oil filler cap and check if you have visible smoke coming out of the cam cover. Might be a failed oil control ring...
Quote:
the pipe that gets air from engine to air filter compartment
Yoou mean the other way round, don't you?

And please don't do this to a cold engine. Wait till the temp meter is showing normal operating temp. It hurts...
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during cold start with couple of mins of idling. Then i did some real high revs
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Old 25th September 2009, 22:58   #15
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Hi,
My 97' carb 800 has the same problem.Like many people have suggested i had done a proper tune up job,the carbon spewing reduced but has not gone completely.

Have been contemplating a carb overhaul later which i think will most probably eradicate the problem.Maybe you should go for a carb overhaul since your car has done pretty much high mileage.
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