[aashishnb]

Originally Posted by V0rtex

I've changed the air filter, cleaned and tuned the carburetor, and increased the idle RPM from 1.2k to 1.8k.

Shouldn't the normal idle RPM be around 800-900. If you're at 1800, something is not allowing fuel to burn properly and you need to look into that. Can you check what is the normal idle RPM mentioned in the user manual?

Higher RPM on idle is also one of the reasons for lower fuel efficiency.

[V0rtex]

Originally Posted by aashishnb

Can you check what is the normal idle RPM mentioned in the user manual?

1400+-100 is what I read online.

[V0rtex]

Update: I've changed the spark plugs. Although the previous ones were good, I decided to replace them anyway. However, the black smoke from the exhaust when fully revved at idle still hasn't disappeared. Does anyone have any clues?

[rajeevsulu]

Originally Posted by V0rtex

Update: I've changed the spark plugs. Although the previous ones were good, I decided to replace them anyway. However, the black smoke from the exhaust when fully revved at idle still hasn't disappeared. Does anyone have any clues?

Black smoke from exhaust means oil is being burnt.Unless oil burn is stopped, your bike will never pass PUC test.

As many people have suggested,get your piston rings changed.Oil should not be burnt, period.

Cheers

[BullettuPaandi]

Originally Posted by V0rtex

Instead of the recommended Honda 20W40 engine oil, I used 20W50 Motul engine oil.

I'd suggest to stick with recommended grade. Using a 'heavier' oil possibly leads to the smoke from exhaust & less pollution control issues you mention, especially in a motorcycle with a wet clutch like yours.

Those numbers '20' & '40' are viscosity grades at cold & operating temperatures; larger number means more viscous/ resistant to flow. So, what you've gone with is an oil, which is more resistant to flow at operating temperature. This might mimic a 'smoother' engine, but is a problem because, it might create too much resistance causing:

1. Less efficiency as the moving parts now have to fight the oil as well.
2. The clutch to slip by sticking between the plates and not flowing out and disengaging the clutch.
3. More heat in the components which only reciprocates to more of the above issues & more wear-and-tear on the components in the long run.

Less efficiency directly results in more pollutants. Clutch slipping & heat might burn some of the oil, again, as the heavier oil would stay there more and accumulate heat. This could directly result in smoke - and therefore, pollutants in it.

Unless your engine was lugging at 1.2k, you never needed to increase it to 1.8k. Except, you had to simply because of this heavier oil. So, this is a simple way to realise that you're making the engine less efficient. The manufacturer has no reason to suggest a lighter oil, when the motorcycle/car can handle a heavier one (as it'd make it feel like a smoother engine). The recommendation usually results in a good balance of performance, reliability & longevity.

Also, if you haven't noticed smoke from exhaust before the oil change, it is likely not the piston rings/oil leak. Besides, oil change is easier. So, I suggest you first test with a fresh fully synthetic oil of the recommended grade - along with other suggestions in this thread - and see what you get.

I also think it is likely that the equipment running the test isn't calibrated well. Try a different location. This is easier than the suggestion that I just mentioned. So, maybe start with this.

Good luck!

[V0rtex]

Guys, I just passed the pollution test! I took my bike to another pollution center, and the folks there were very friendly and helpful. When they tested it, they found my CO level to be around 8% immediately and stopped the system. If they had continued for a bit longer, it would have registered my bike as "FAILED" in the system and flagged it from being tested again for another 24 hours.

They told me about a nearby mechanic and suggested I bring him over to tune the carburetor while they were testing. I went to the mechanic, explained what had been done, and as they started testing again, he began tuning the carburetor. Voila! My CO level dropped to 2.3%, and hydrocarbons dropped from 156 (which was still way below the 3000 limit) to just 10. I was truly surprised, as every other mechanic I consulted wanted me to do complete engine work.

I'm really relieved as I didn't want to abandon this workhorse. I would like to thank each and every one of you who tried to help me.

So, in short, if you fail the test, change the oil and spark plug, and bring the mechanic along with you while you test the bike.

[BullettuPaandi]

Originally Posted by V0rtex

tuning the carburetor

Did you ask the mechanic what was wrong & what the fix was? Was it just running too rich this whole time!?

If it was this simple, I think the first mechanic by mistake messed with the mixture screw as well while adjusting speed screw.

[V0rtex]

Originally Posted by BullettuPaandi

Did you ask the mechanic what was wrong & what the fix was? Was it just running too rich this whole time!?

If it was this simple, I think the first mechanic by mistake messed with the mixture screw as well while adjusting speed screw.

The mechanic was a 'do more work and talk less' type. I thought the bike was running too rich. He adjusted the carburetor as they were testing, and suddenly the pollution parameters dropped. I guess you were right about the first mechanic messing up the work. This guy has wanted to rebuild my engine for quite a while now. Last time I had some trouble cold starting the bike, he told me that I needed engine work. I think I might have found a new mechanic now, lol!

[BullettuPaandi]

Originally Posted by V0rtex

This guy has wanted to rebuild my engine for quite a while now. Last time I had some trouble cold starting the bike, he told me that I needed engine work. I think I might have found a new mechanic now, lol!

..also, the slickest in the world! Gaslighting couldn't get any more literal than this!

[humyum]

From what i learnt from my Maruti 800 days, tuning the carburettor should always be done on a PUC machine and that's what the Ravi automobile guys in Ghatkopar used to do for carburatted cars. With this approach the mixture used to always be in perfect balance of power, mileage and pollution.

[RD410]

Originally Posted by V0rtex

My 2013 Honda Unicorn, which I use for local commutes and errands, just failed the pollution test twice. I’m worried that my bike will fail again if I retest. Do you have any advice?

My 2015 bs3 Dio HET also failed PUC test twice. It's my daily commute, which is maintained religiously. I change oil between 2500-3000 kms, use Castrol 5w40 fully synthetic oil. The spark plug, air filter everything is replaced duly. Carburettor is clean, the scoot gives consistent 50-55kpl FE. There is zero oil consumption or compression loss. Yet it failed PUC twice last week. They are saying that the scoot is showing CO levels of 4+ (the limit is 3). I honestly don't know what to do : (

I tested at 2 different pollution centers. Both of them told me that the govt has done some tampering with the software and that most bs3, bs4 and even some bs6 vehicles are failing PUC. I smell something really fishy here. Fine for not having PUC ranges from ₹1k-2k. I won't be surprised if our MVD suddenly starts cracking down old vehicles for PUC verification. As you know, how much our govt loves looting people through fines

For one, I had already guessed that my Dio will fail the test. Because first my friends well maintained bs6 Activa 125 failed. Then another friends well maintained bs3 Unicorn 150 failed. So it was obvious that my scoot too will have the same result.

[V0rtex]

Originally Posted by RD410

. So it was obvious that my scoot too will have the same result.

Please follow the advice given in this thread. Take a mechanic along with you when you do the pollution test.

[gb97ce6]

Slightly off topic but I think KL cops are well trained to fleece money from out of state vehicles , though they are simply following the law.
Had a really bad experience last year during our diwali trip. Right after we crossed the border we were stopped and the very first question was - “ can you show your PUC” . Paid the fine and left and within the next couple of hours we were stopped at every single jurisdiction we crossed. what the hell , TN cops have never asked for PUC so most here do not bother with the certificate renewal.
And the cops in KL also warned us that the fine was valid for only 24hrs and suggested we get PUC cert right away, as if we came to KL to get this crap done. Well done guys to welcome tourists spending their hard earned money in your state.
Again , they were polite and friendly and just doing their job but it still pissed me off knowing the fact they were preying on out of state vehicles asking specifically for PUC and nothing else. It saves their time I guess rather than looking through license and insurance papers which pretty much everyone will have.

I am not sure if this was a one off incident or if others experienced it as well but anyone planning to travel through KL better get the PUC done

[swiftnfurious]

Originally Posted by gb97ce6

Slightly off topic but I think KL cops are well trained to fleece money from out of state vehicles , though they are simply following the law.

...
I am not sure if this was a one off incident or if others experienced it as well but anyone planning to travel through KL better get the PUC done

You happily flout the law and blame the law enforcement for your mistake?

When it's legally required to do a PUC, what stopped you from keeping it ready especially when you had to travel interstate?

It hardly matters if any police is asking or not asking to keep the PUC or other documents, as a vehicle owner, we are supposed to do the required tests and keep everything in order. It's just not KL police, Goa & KA do the same and few other states do it as well.

And no, KL police doesn't single out outstation vehicles or fleece them - they take the very legal route and don't take any bribes as well, the money goes to government. I was fined in a KL vehicle for not complying with the right size number plates (never knew I had a wrong size one as I got it done in a reputed shop).

No harassment, super polite, paid the fine in mobile court and made a new "to-the-spec" number plate and never stopped again in 7-8 years or more.

PS : and unlike the PUC centres in TN who charge 2-3x of the actual test costs, KL levies the rate government fixes. Not a single extra rupee charged and there are lots of PUC centres available even in small towns to get it done.

[kozhissery]

Originally Posted by gb97ce6

Slightly off topic but I think KL cops are well trained to fleece money from out of state vehicles , though they are simply following the law.

I defer to agree with you. I'm a Keralite and I've been stopped quite a few times and only twice was charged, once for going overspeed in bike (barely 5KMS above but technically I was wrong) and once for high beam inside the city. Rest all the times, just checked the docs/seat belts etc. and let me go.

I think the reasons for BS3/BS4 vehicles failing is that these engines were made for BS3/BS4 fuel and the mechanics increase/tamper the fuel/air mixture to avoid sputter (in non FI engines for sure). I can say from my experience that after the mechanic tuned the vehicle to pass the test, the idle speed is low and the vehicle dies if throttle is not given.

I think this PUC is linked to national portal and not state portal, so I don't think that the state has any control over the PUC machine or software.

I think our esteemed members who are working in this field would be in a better position to say why PUC is failing after the software/hardware upgrade.