Re: Honda Trigger_Engine prob @ 22.5k kms(Bent valve, changed, still black smoke from exhaust)

Topic Approved.

You must never service outside the authorised SVC, now you can't claim Honda for warranty or the SVC for damages due to service.

Are you sure Air Fuel ratio is set properly on the carburetor?
Secondly, have you taken all original Honda spares, and that too for your bike's model year only? (because the valves getting bent suggest otherwise).

Now, its hard to spot which thing is causing the trouble, it may be the carburetor that's not set well, it could be oil leaking into combustion chamber, it could be a lot of things.


[MENTION=32286]psr[/MENTION] sir could you help this member?

Re: Honda Trigger_Engine prob @ 22.5k kms(Bent valve, changed, still black smoke from exhaust)

Looking at the bent valve one can clearly see that the valve stem had rubbed against the valve guide from top to bottom...This is not a good sign . secondly, the valve can bend only if it is stuck and the piston had hit it at part open condition or the rocker had literally hammered it to open position...either case it could be manufacturing mistake ,ie., .
If you are a rider who frequently blips open the throttle, and your timing chain had got very loose, then also this can happen.
One of the common reason is OLD PETROL in Tank...If you ride the bike once in a week, and fill petrol once a month or beyond that, then old petrol will turn into Varnish like consistency, and can lead to jamming of valve in the stem. This may be the case in your bike since it is the Inlet Valve which had been bent...

Black dry soot on the spark plug and the exhaust end is an indication of rich AFR.. get the carburetor setting corrected, and check Choke for remaining open even when you close it...

Re: Honda Trigger_Engine prob @ 22.5k kms(Bent valve, changed, still black smoke from exhaust)

Till I was in chennai, was doing in honda SVC only but when I went to nearby pune SVC for sudden stalling of engine and those guys dint even di agonise the faulty air filter. Anyways, am in discussion with HONDA claiming this to be a manufacturing defect since it has happened in 22.5k kms only though I have been properly changing oil etc. The case is still in Honda discussion, fingers crossed. .

AFR is what I am also doubting now after the recent service.

Carb was cleaned twice recently before th3 actual engine tear down.. Spares, I do not know since I was not there that day :-(

From engine tear down view, I don't think oil is leaking into the combustion chamber...

If honda declines, will go back to my mechanic to further probe on the problem.. Feel sick off late after this bike has developed issues even after regular and proper care...

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But from the service bill, I don't think my mech has changed the valve guide :-(

AFR, will get it checked this week. Just checking for the mileage now to clarify AFR doubts..

Also, I don't blip open the throttle, am basically a smooth rider but took the bike for uphill ride twice (June and september), both the times, even in 2nd gear, bike will struggle, I think the issue was long lasting and just now showing up issues :-(

Old fuel, ruled out since I commute to office in this bike daily...

Carb was cleaned twice recently, Reg choke cable, since it was rusted at the bottom, the mech sprayed some oil and said it is fine, replacement was not needed.

The cold idling is now 1k and hot idling is 1.5k and is stable from what I saw..

But what can be the manufacturing defect exactly!!! Valve setting or rocker arm adjustor or the timing belt or anything else!!!!

Re: Honda Trigger_Engine prob @ 22.5k kms(Bent valve, changed, still black smoke from exhaust)

Valve cannot bend unless it had got stuck while operating and either Rocker arm or piston slams on it...so either of the problem definitely had happened . Dry black smoke indicates rich AFR...check spark plug for similar dry soot coating...
Since you had ruled out all of the possibilities I had suggested, I am at a loss to understand what might have happened to your engine..

Re: Honda Trigger_Engine prob @ 22.5k kms(Bent valve, changed, still black smoke from exhaust)




With expert advice, i tot i can sound sensible while fighting with Honda for warranty even after servicing outside, claiming this to be manufacturing defect.

More than this reason, i wanted to set my bike right Always had scooters at home, this was my first bike and feels close to me (off late, losing the love towards it, had taken care of it that much still it is troubling me )

Anyways, fingers crossed and seeking more advice from experts

Thanks a ton friend.