[V0rtex]

Do you have any tips for passing the pollution test? My 2013 Honda Unicorn, which I use for local commutes and errands, just failed the pollution test twice. Six months ago, it passed with a CO level of 1.15% at idling RPM. Now, it recorded 3.17% (the emission limit is 3.00%). The bike was due for service and was running low on oil. The next day, I took it for service where the air filter and oil were changed, the carburetor was cleaned and tuned. Instead of the recommended Honda 20W40 engine oil, I used 20W50 Motul engine oil. The mechanic also adjusted the idle RPM, increasing it from around 1.2k to 1.8k.

I read online that riding the bike hard for some time before the test might help remove deposited carbon. Following this advice, I rode my bike hard, hitting the rev limiter for several kilometers. I then took it to the pollution center again immediately, but let the bike cool down before testing. Whenever I hit the rev limiter on idle, it produced grey/black smoke. The pollution center technician mentioned he smelled burning oil.

I tested again and got a reading of 7.15%! I was shocked. He told me that 80% of the BS3 and BS4 vehicles are failing the test due to some new updates by the Kerala government. Two other people with BS3 vehicles also failed the test, despite one having done complete engine work and service.

I’m worried that my bike will fail again if I retest. Do you have any advice?

[vrprabhu]

I had to renew the registration of my 2009 Gladiator and was apprehensive of the emission test. But, the bike sailed through the test a couple of weeks ago. In fact, I did the servicing (oil change, air filter cleaning & chain lube myself). Didn't clean the carb; instead, waited for reserve and then filled 500 Rs. worth XP95. Drove continuously for 50 kms at varying speeds. Hopefully the carb is flushed clean.

Coming to your issue, I think the grey/black smoke from your exhaust indicates that there is oil leakage in the engine. May be worn out piston rings?

And, check whether the air filter was really changed (not reused after blowing compressed air through it).

Any doubts regarding the fuel quality? If so, Jio pump quality seems better.

Hitting rev limiter is the Italian tune!! Don't know if it will work for a 150cc engine?

I think the unicorn has a exhaust scavenging port; get it checked for accumulated debris. Also, check the choke cable and its play as well as condition of the spark plug. This will give an idea whether the engine is running rich or lean.

BTW, how many kms has bike run?

[V0rtex]

Originally Posted by vrprabhu

And, check whether the air filter was really changed (not reused after blowing compressed air through it).

Any doubts regarding the fuel quality? If so, Jio pump quality seems better.

Hitting rev limiter is the Italian tune!! Don't know if it will work for a 150cc engine?

I think the unicorn has a exhaust scavenging port; get it checked for accumulated debris. Also, check the choke cable and its play as well as condition of the spark plug. This will give an idea whether the engine is running rich or lean.

BTW, how many kms has bike run?

The air filter was changed in front of me. I took my bike to the local mechanic. The official service center gave me an estimate of 15k last time—they wanted to replace everything, even the footpegs and switches, which were perfectly fine. They also take a lot of time to service the bike.

I think the bike has run around 60-65k km. I also noticed that when I put my finger in the exhaust hole, there is a lot of black carbon deposit there. This has been the case for a long time. The spark plugs were replaced 8 months ago. Would changing them again make any difference? I really don't want to do any engine work on this bike, as that would be quite expensive. I use it just for short local commutes.

[vrprabhu]

Changing spark plugs won't help, if there's a fault with the engine. Is the spark plug tip black & oily? Indication of excess oil in cylinder.

The mileage indicated suggests that the engine needs to be looked into. Piston ring change is not a major or costly work. There could be a minor wear or minor slack in the timing chain, which can be adjusted, for cleaner combustion.

[Jeroen]

Originally Posted by V0rtex

the carburetor was cleaned and tuned.

I’m worried that my bike will fail again if I retest. Do you have any advice?

Once an engine is properly maintained the CO level on most bikes/engines/cars needs to set separately. It’s part of tuning the carburator!

They will tell you that on some carburettors it is not possible to adjust the CO level. But that is rarely true. On some carburettors it is quite complex as you need to take it apart and reset it multiple times.

You are much more likely to have a low CO level with a properly warmed engine than a “cold” engine.

Good luck

Jeroen

[V0rtex]

Originally Posted by Jeroen

Once an engine is properly maintained the CO level on most bikes/engines/cars needs to set separately. It’s part of tuning the carburator!

They will tell you that on some carburettors it is not possible to adjust the CO level. But that is rarely true. On some carburettors it is quite complex as you need to take it apart and reset it multiple times.

You are much more likely to have a low CO level with a properly warmed engine than a “cold” engine.

Good luck

Jeroen

I’ve been doing the Italian tune quite a bit recently. I also plan on adding the Yamaha Carbon Cleaner. The mechanic has increased the idle rpm from 1.2k to 1.8k, would that have any impact on the CO level. Right after this has been done, I took it for testing again and to my surprise I got 7.5% CO.

[Jeroen]

Originally Posted by V0rtex

I’ve been doing the Italian tune quite a bit recently. I also plan on adding the Yamaha Carbon Cleaner. The mechanic has increased the idle rpm from 1.2k to 1.8k, would that have any impact on the CO level. Right after this has been done, I took it for testing again and to my surprise I got 7.5% CO.

Italian tune won’t matter for your CO level. Idle does! Idle and CO always needs to tuned together.

Jeroen

[V0rtex]

Originally Posted by Jeroen

Italian tune won’t matter for your CO level. Idle does! Idle and CO always needs to tuned together.

Jeroen

How should I do that?

[Jeroen]

Originally Posted by V0rtex

How should I do that?

You need to find somebody who knows what to do and has the equipment.

Sorry, without a CO analyser there is no way of knowing what happens when tuning an engine.

Jeroen

[kozhissery]

My 14 year old Activa was always being maintained at the company showroom and I was confident that it would pass the test, alas it did not. The person asked me to give it to any local shop and not the company showroom as they don't change the required things. When asked about where to give, they suggested almost all the local shops which repaired Activa. He even mentioned that to inform the service advisor that it failed the PUC test. I just took the activa to the nearest shop and mentioned the issue. He said most probably the spark plug/filter/oil needs to be changed/cleaned, so asked him to do full service and get the PUC done (with additional fees).
I got back the scooter next day with the new certificate and a bill lot lesser that what is usually charged by company showroom. Only the filter and spark plug were changed, according to him oil is in good condition.

In short, there would be shops who does the job of getting the PUC after servicing your bike too. One thing that I've noted is that, now you have to give accelerator to keep in idle, else the scooter will die.

[V0rtex]

Originally Posted by kozhissery

In short, there would be shops who does the job of getting the PUC after servicing your bike too. One thing that I've noted is that, now you have to give accelerator to keep in idle, else the scooter will die.

I've taken it to a local mechanic and made a few changes. I replaced the oil with 20w50, whereas Honda usually uses 20w40. I chose a higher viscosity oil because I saw in the service manual on TeamBHP that 20w50 is also an option for the Honda Unicorn. I've changed the air filter, cleaned and tuned the carburetor, and increased the idle RPM from 1.2k to 1.8k.

To my surprise, when I did the pollution test again, the CO% increased by 2.25 times (from 3.17% to 7.5%). I should note that I did some 'Italian tuning' just before the pollution test, riding the bike hard for around 10 km. Now I have added Yamaha's PEA carbon cleaner along with around 5-6 liters of fuel. I'll continue riding it hard and then do the pollution test again.

[omranga98]

Well, I had a stranger issue.

I took my Taigun for PUC but it failed since it registered 0% pollutant according to the device and if the result is 0%, the certificate would not be printed.

The testing machine was fine because it had just tested my Ignis and a Brio before me. Turns out it is a rather common issue that a lot of BS6 cars face (?) As ridiculous as it sounds, I tried the following day and it worked.

[dodgem]

My Royal Enfield (2005 Electra 4S) failed pollution test twice. After the first failure, my mechanic attributed it to low running and old fuel inside fuel tank. We emptied fuel tank, cleaned carburetor. It did not help, the test failed again. I was running on stock spark plug, yes never replaced it in 20 years. So, I replaced it with normal Bosch Spark Plug and voila it worked.

[maheshm619]

Originally Posted by V0rtex

Whenever I hit the rev limiter on idle, it produced grey/black smoke. The pollution center technician mentioned he smelled burning oil.

Do you have any advice?

CO is a by-product of improper combustion or insufficient oxygen / air. I guess your fuel/air ratio is too rich. If the bike is returning poor average, then it can be confirmed.Get the carb tuned by a good mechanic and also get the spark plug checked. I had a similar black smoke issue in my old NTorq scooter when the carb tuning was poor.

[amit_purohit20]

1) Use carbon cleaner additive in the petrol. Perhaps a little more than stronger mix with petrol will help you clean carbon deposits.
2) If your silencer is choked please remove it and get it heated and carbon removed or flush it with high pressure water.
3) Smoke coming out of silencer indicates burning oil so just replace piston rings with a fresh set. Do not do anything else even if the mechanic suggests.
4) As Jeroen mentioned do the PUC when the engine is warm. I do not suggest any Italian tune up as I have no idea on its effect on emissions. Just load the engine make it warm and go to PUC. If you want to load the engine you can go double seat over flyovers and probably higher gear it warms the engine faster. I do not suggest getting the engine too heated up, as with heat the bore expands and probably a bigger gap between piston and bore might lead to more oil burn up.
5) Take it to the authorized showroom where they would set the carb to meet PUC. They have electronic instruments to give real time emission readings and thus can tune the carb.