#1. Colourless or slightly blue smoke from exhaust
This means that your bike is very good condition. What you can assume is your fuel/air mixture is at the right composition and everything is well burnt is your combustion chamber.
#2. Yellow or brownish smoke from exhaust
Your fuel/air mixture is too lean. Too lean means that there is low fuel but high air mixture in your combustion chamber.
Solution: Adjust the fuel/air mixture at your carburetor (or ECU) accordingly.
#3. Black smoke from exhaust
Your fuel/air mixture is too rich. High fuel but low air intake. This will reduce your fuel efficiency since the black smoke is your unburnt fuel.
The problem might be at this part:
i. Your air filter is dirty or blocked from receiving air from surrounding.
ii.Your choke is closed
iii. Your carburetor is damaged
Solution:
i.Clean/replace air filter
ii.Open choke
iii.Repair/replace your carburetor.
#4. White smoke from exhaust
This happen when your engine oil gets into the combustion chamber.
The problem might be at this part:
i. Piston ring is loose
ii. Piston is worn out
iii. Engine block is worn out/scratched
iv. Valve is worn out/damaged
v. Valve line is worn out/scratched
Solution:
i. Replace piston ring
ii. Rebore block and replace piston
iii. same with no. ii
iv. Replace valve
v. Rebore valve line and replace valve.
Sometimes white smoke can also occur in the morning or you start your bike after it is being left on the rain. The white smoke is the water vapour released from the condensation that happens inside your exhaust. Normally, this happens only for few minutes and then it will be back to colourless again. The difference from white water vapour smoke and white exhaust smoke is the smell. What I can say is, the smell from engine oil being burnt is your combustion chamber is bad and very busuk. Water vapour doesn’t have any smell.
Source: http://motomalaya.blogspot.com/2008/12/knowing-your-4-stroke-bike-engine.html
43 Comments
hi sir i got hondacbtwister 110cc bike i love my bike this morning i have noticed after i startup my mill there is a slight smoke from the
silencer important thing is i was not used my bike for few days and also
i left my fuel knob in on position after i ride about 5 minutes i didnt notice any smoke i scared something problem to my bike please help me give some suggestion thanks
Hi there,
please do not worry.. your bike has no problem at all. Because you have not used your bike for days, water vapour accumulate in your exhaust system. Therefore when you start your bike, slight white smoke come out from your exhaust.
But as you have noticed, after riding for about 5 mins, you do not have smoke coming out anymore. This shows that your engine are still in good condition.
Hope this helps
Hi,
I have a honda unicorn sep08 modes. recntly i have noticed thick smoke coming from silencer and the oil in the gear box geting drained quickly
i need your suggestions and remarks.
Hi there, your piston rings are worn out. When your piston rings are worn out, oil from your gear box get into the combustion chamber. That explains why there is a thick smoke coming out.
I strongly recommend that you replace the piston rings to fix this issue. If you do not replace the piston ring, oil will keep on getting drained into the combustion chamber. This will result in insufficient oil to lubricate your gear box, causing serious engine damage!
In the meanwhile, do check on your oil level and top up when necessary to ensure there is enough oil to lubricate your engine!
hey i was just seeing i have a xr80r Honda 1988 and when i start it up smoke comes from the exhaust and we thought it was just vamper at first but then we could smell it was oil burning so i dont now what to do and their are little drops of oil from the exhaust thanks here back
Your Honda XR80 is a 2-stroke. Smelling burning oil is normal in 2-stroke engine. It is also perfectly normal to have little drops of oil from the exhaust. Those are unburned 2T oils.
i got told it is a 4 stroke and also thick white smoke comes out the exust
Check out your piston rings. Your piston rings are worn out and engine oil is being combusted during the combustion process.
That explains why there is a thick white smoke coming out of the exhaust. Do also check on your engine oil level. As engine oil is being combusted during the process, your engine oil level will get lesser and lesser. Do top up if necessary to prevent any further engine damages.
and my bike will not idle so is that the reason that thair is oil on the combusted chamber is that why bit wont idle
yes. Your combustion process is being screwed up…
My recently bought cb unicorn oct’10. I’d seen white n smelly smoke from my silencer. So i got my bike to mechanics n they changed piston, piston ring, valves. But the problem is when i start the bike for the first time the same smoke comes out for 10 ~ 15 mins. After it doesn’t come. And again when the bike rest for 2~3 hours again smoke comes out. What is the solution? (just it became 3 days i replaced piston, piston ring, valves.)
It could be cold starting. Those white smokes could be vapor. Did you notice any performance issue after overhauling?
@Willie
nothing change. But that smoke smells and lots of lots of smoke comes out. I don’t think so it’s vapour. And after putting rest to bike again smoke comes. It happened all 3 days after replacing piston, rings, valves.
check your engine oil to see if there are any loss in volume? Let me know.
@Willie
no engine oil is not reduced. It’s same full.
If the engine oil volume is the same, it means that no engine oil has been combusted.
As for the smoke, I am really confused. By right after replacing your piston rings, there should be no such problem since no engine oil will get into the combustion process.
Hmm.. you check your radiator coolant level? I suspect that the coolant might get into the top cylinder.
No there is not.
No there is not. The mechanics told me it could come upto 700~1000 km. Then after that it will not come. So……
This is funny. It couldn’t be. Running-in does not caused white smoke. But anyway, just wait till about 700 ~ 100km and see how it goes.
Do post it here and let everyone know!
@Willie
so do you’ve any idea? My bike is honda cb unicorn 150 cc. And the mechanics told me that there is something is silencer n those smoke is from the old engine oil. Which it’ll slowly reduce n completely goes. So do u think it can be??!!??
I don’t believe what your mechanics said. But I do not know what is the problem since there is no loss of engine oil.
I think you just have to wait and see.
@Willie
Hi willie,
I again went to my mechanics and i told him to open or down the engine and the piston….. so he found the ring of piston moved and came to one place, so from that place the engine oil moved to combustion chamber… so the smoke was comin from exhausted pipe…. and he replaced the ring and maintain the position of the rings. after that the smoke isn’t coming…….
Yeah, a wore out or displaced piston ring will caused engine oil to get burn in the combustion chamber. As such, white smoke is coming out from the exhaust due to the engine oil burning.
You should have a decrease in engine oil volume when you noticed this problem
@Willie
ahh…not but if small volume of engine oil is decreased than i don’t konw. but i frequently checked my engine oil level but i think it’s not decrease, then n now it is in max level. so i was lil bit confused
AND VERY VERY THANX FOR THE SUGGESTION AND UR OPINION…:d
@Willie
ahh…not but if small volume of engine oil is decreased than i don’t konw. but i frequently checked my engine oil level but i think it’s not decrease, then n now it is in max level. so i was lil bit confused
AND VERY VERY THANX FOR THE SUGGESTION AND UR OPINION… ☺
No problem! ENjoy your ride!
Hi i was just wonderin i was riding the other day and my bike stopped and there was oil dripping from the air filter box. I have changed all the oil in the bike now and wen i go to start it now there is water coming thru the exhaust and my radiator looses water
And the bike does not start
Your radiator lose water? Most probably your coolant went into your engine combustion chamber. Please remove the top cylinder and take a look!
Hi, I replace piston and piston ring, rebore the combustion chamber in kinetic blaze but their is light blue smoke coming out from silencer. My mechanic set the engine at 2100 rpm, he told me their is new piston and valve so n their is some oil their so its going out n he also told me we have to set valve after some riding not to much speeding. What to do ? Please help me I love my blaze.
So you are done overhauling your blaze engine? Personally, I think that the idling speed of the engine at 2100rpm is very high. You should adjust it to around 1.4 ~ 1.5 K rpm. By the way, there shouldn’t be any smoke coming out from the exhaust. Please check your engine oil level the next time you change it. Keep me update.
Thanks, As you say I checked oil level it on max but when my mechanic overhauling blaze piston & valve he did not change oil. So that the reason smoke coming out from silencer or he did not set valve properly. If I change oil smoke will gone or I have to recheck piston & valve setting.
Most of the time after overhauling, we don’t reuse the engine oil. Check the piston ring. Maybe the piston rule is not “sit” properly which results engine oil being push into the combustion chamber.
When engine oil is being push into the combustion chamber, it will be burned and white smoke will come out from your exhaust.
Hi sir i got a white smoke when i was riding bike.. heavy smoke.. with some oils at the edge of the silencer. i have rided only 11,600KM only. please advice me..
your piston ring is badly worn! Please replace it as soon as possible!
I have a honda shine. While refilling engine oil I found the level is very low, i.e. the capacity is 900ml but only about 100ml came out from the engine. Refilled with the Honda engine oil (900ml). but in next refill again I found nearly 200ml of the remaining oil from the engine. Recently I observed that Driving in low speed (below 50km/hr) there is no white smoke from the silencer, but in high speed , above 50 km/hr, white smoke is coming out from the silencer of the bike. What could be the reason and what shoud be done to solve the problem? Please suggest. Thanking you. DKR
Hey DKR,
It is obvious that your piston ring is worn out. When you are riding in low speed, there is no white smoke because the piston cycles are lesser. Hence, little engine oil is being “slipped” into the combustion.
As you ride at a faster speed, the piston cycles are higher and this forces the engine oil to slip through the piston ring and go into the combustion. This also explains why there is white smoke coming out from the exhaust.
I suggest you change your piston ring to avoid serious damage to your engine.
Let me know if you are still having problem.
Thanks!
Hi Willie
I have a LML NV 4 STROKE scooter covered only 450kms. My scooter engine has been opened and repair at aforsaid kms by authorized LML dealer due to piston seizure as told mechanic. Please tell me what was the reason of engine opening.
I found before engine opening ‘engine oil leakage from chain tensioner.
Thanking you.
RKS
Hi,I have a pulsar 150 and it is only 1 yr old.After servicing on last thursday,I have seen that when I start my bike after a long time interval (8-10 hrs) either in morning or in evening,heavy white smoke with some raw fuel smell comes out from exhaust but after 1 min,smoke disappears.
Please let me know what is the problem and how I can get rid out of it.
hi i have a passion pro. recently a week before i changed my clutch plates and engine oil. after 2 days some white smoke is coming from the silencer. my bike is running good. but after a day because of some oil accumulation on plug, bike doesn’t start so i need to clean the plug. mechanic says your engine needs to be open, piston and other things need to be changed. is it necessary to open the engine or there is some other solution. and is it necessary to change every thing in an engine whenever it is open for repair.
hi how much do piston ring sof honda unicorn 150cc cost approxiamately
I recently bought cb unicorn Feb 2012, and run around 2300 KM and yesterday i found smoke is coming from the silencer (something black color) while accelarating, when i check the engine oil the oil level is less and also after running 5-10 KM some burning smell also coming.
Please let me what is the exact reason, is there any problem with engine????
Probably your piston rings are worn out. Please try replacing them!