in the above pic i didnt get what do u mean by head oil supply gallery o-ring and its position. how do u knw by looking at the head if the afr is lean rich or perfect? and what does dry and wet carbon signinify? and do the marks on the head mean engine opened, rebored,etc,etc?

1. The Exhaust Valve...should be Tan color, which the Valve is..so combustion Temperature is acceptable..

2. The In Let Valve...will be dark and with slight deposits...which is same in pic..so further confirms AFR being almost correct..

3. The Head Gasket inner Boundary....it is circular and even...as it should be.

4. Here the Burnt oil /combustion residue had seeped past the gasket staining the head...so obviously the head Gasket had failed , in this area...

5. Trace of Liquid Gasket sealant Three Bond...Stock bikes are bolted on with out this sealant, and only when the engine is opened and put back is the sealant used..

Since the carbon deposit seems wet , an engine oil leak through Stem seal or worn Piston rings was suspected...

thank you very much for the detailed explanation....learnt many things

Excellent conclusions PSR.

@PSR,Paul,Mayank
I will reply to all the messages once all the other members finish posting their views.(Still waiting for Sibun,pinaki and others to post)

Note :- This engine was running excessively rich before tuning it. The head was removed just 800 kms "after" tuning/adjusting the AFR.This bike was subjected to high speed riding just before head removal.Some dislodged particles even managed to scratch the bore lightly.

"It is so light that it can not be felt even by sliding the tip of finger nails over it."


Oil level remains "almost" the same through-out the drain interval of 2000 kms(Some 30-40 ml is lost in 2000kms). Silencer tip has normal level of soot/carbon. There we no hard deposits in the exhaust port.

is that gap between piston and cylinder fine? i have never seen a pic so closely like this so dunno how much clearance is acceptable...

and there arent too much deposits on the piston..some light ones? or is this much called "too much".

how to avoid or atleast delay carbon deposit formations...running lean/rich perfect? timely oil change,etc.etc...tips please....thanks a lot shoeb..learning so much through this initiative...

Regarding the pic of cylinder head: would like to add only one view to psr sir's insights. I guess this engine has faced knocking, because I see considerable amount of carbon deposits dislodged.. Regarding second pic, the piston, looks clean, can also figure the color of it. running too rich. as Shoeb, you have already stated. Guess there's too much fuel to wash off oil film in the cylinder. Piston color should be brown or tan. brown is what I like, means little richer than 'perfect' tuning, helps keep the engine stay cool..

I read somewhere that exhaust valve should be red coloured , as it indicates correct mix . Plz correct me if i am wrong as i am a newbie .

I had a question...as psr mentioned there are sealant marks and hence engine is opened before and gasket is replaced and fixed with sealant.

so why does the engine from factory dosnt use sealant? how does gasket stay properly without sealant from factory but when we fix it needs sealant?

plus there are marks on the head..seems like a nail has been hammered on it... does that have anything to do with engine opened?

Actually no sealant is required on any gasket. If your mating surface is plain then installing a new gasket doesn't required sealant. Sealant only helps to makeup/fill the gaps if old gasket is re-used only if its condition is fine.... but head gasket is never re-used, because those are metal and get compressed after installing. So when opening new gasket is required.
Sealant is not required on head gasket too but we still use it because it helps to seal better. I mean, its very cheap and cost only Rs.10. So applying it just gives u a satisfaction and assurance/certainty that it will not require any open later. I mean, will fitting we not need to worry if that leak or fail later.
For other gaskets, like top cover gasket, side cover gaskets, clutch cover gasket. I didn't use sealant on these, and they run without any leaks.
Few days ago, i re-open my clutch cover and re-used the same gasket (coz it was new) and that too without gasket sealant and its running fine without any leaks.

Reading nail mark-
On factory fitted engine there would be no marks like that. These marks appear when we open and that too came because of.... we can say, some carelessness or something.
If something got hit. Or when we remove valve spring cotters, we use hammer. So hitting with hammer without any cloth on its mating surface may put mark on it.
Moreover, if head is given to the lathe for valve polishing. Those guys use vice to hold head. May those marks appear through vice. Or they keep those head on ruff cemented floor, with all those stuffs floating around like nuts bolts, valves, dice, cutter, hammer and lots of things.....so those marks come from working in those conditions.

So basically, factory fitted engine came without any marks. If u ever open the head and found any mark, that means may someone had opened and worked on it before.

I have never allowed a mechanic to use gasket sealant etc on my bike's engines for the fear that it shall increase the distance between the two parts and become different from the original design . Is this right ?
Also I found that HeroHonda gaskets has changed at their parts dealer now . Earlier we were getting the black-ish colour gaskets made of asbestos ( I think) and were reusable a few times (they told me that) . The new supplies are of a green colour paper (feels synthetic) , dunno what it's made of but it's usable only once (this is also from the authorised parts dealer) . Can somebody throw more light on this ?

Not only in bikes but in life, man must never forget his humble beginning. Many people forget their humble beginnings once they move up in their life and forgets about the days when they were struggling, I have seen many such cases and really feel sad to see. This trait is found in only human beings but all other animals never forget their humility. Take the example of dog, once you have regarded it with affection, no matter even if it sees you after 5 years it will wag its tail and will be very happy to see you, but human being after getting their work done will turn their face the other side. This also is applicable to bikes.I have one such story which i will send in PM as i do not want to post in public forum.For the pictures here is the conclusion:-1. The bike was running with duplicate head gasket as the air mixture was leaking and also the rubber protector of timing chain is stuck to head, instead of getting removed from bore with the head packing.2.The bike was running lean which is expected and the leaking air fuel mixture would make it lean.3. The bore is alright but oil was leaking from the small o-ring which brings oil to head.- You can see the mark of oil channel on the bore mating surface. What was happening was oil was getting sucked in suction stroke- it will not smoke because oil was getting burnt in firing completely as oil was very less in each stroke.4.The carbon deposits are more because of rich mixture the bike was previously running than because of oil. After making the mixture lean the carbon became hard and you can deduce from the white and reddish patches on the carbon.The bike has no problem, but a duplicate gasket and duplicate o-ring is the cause of all problems.For knowing the correct color of valves, open the post where i have posted my bikes head opened picture, you will get the exact color of valves and carbon for perfect mixture.Factory engines have the mating surface perfect and thus no sealant is required. If you are using original gasket after opening then also no need of sealant. But a light layer of sealant is applied on the bore peri-feri so that if in future the gasket shows fault then the compression neither combustion mixture will leak from chamber.NO, DISTANCE will not increase as the sealants are of rubber type and once applied and when we tighten the head bolts then they compress like paper gasket, even if distance increases then it is in few microns and nothing else. In-fact in our horizontal engines if there is slight timing chain noise and if we have opened the head after cleaning then if we use sealant then the noise will go away as the few microns increase in height will take away the play from chain.Regarding the gaskets then it is the result of BS-III environmental policy as the black gasket were made of asbestos and thus can be re-used but the new green gaskets are nothing but several layers of papers sandwiched and made from waste papers. Once compressed they need to be replaced.There are two benefits:-1. Environmental- as the asbestos were carcinogenic so better to use paper. Also paper are eco-friendly and also re-using of waste paper is beneficial.2. Profit- It costs less but MRP is same, so more profit, also each time gaskets need to be replaced, so more profit.

Whoa ! Exact and precise analysis,Sibun. This is something which comes only by experience.

If you have some pictures like these,please post it here.

Waiting for your PM.

I think that the bore gasket is still made out of asbestos or something similar,no ?
Overall it is a good move to have paper gaskets ,non-asbestos brakes etc as mechanics are also humans and dealing with carcinogenic stuff every day would mean decreased life expectancy. They are also dipped in used oil from top to bottom which is very harmful.

@Pinaki
In petrol engines "slight" increase or decrease in the deck height(Say due to re-surfacing of the head/block) is not of much an importance when compared to diesel engines. In diesel engine one has to go through some precise calculations and choose an oversize head gasket.(Yes,oversize gasket for diesel engines are very common)

Increase of half a mm causes some significant difference in the engine's charecteristics , like you said sometimes it may be of benefit by taking up some slack or shim like that , but the compression ratio changes and some unpredictable things may happen too . So I don't like it . I have also never let them use a knife, screwdriver or similar tool to remove the old gasket material . That is what damages the prefect mating surface in the first place and causes oil leaks . If it isn't comming off easily , soak it in oil/kero/solvent and let it sit and try again with fingernails/old credit-card only .
If those new gaskets are paper only it's very sad , they won't withstand heat and pressure anywhere near the asbestos ones . No wonder I keep finding oil leaks in every other engine I see today .
To get asbestos poisoning the mechanics have to grind these brake-liners and gasket material into powder and then sniff it . The asbestos in them is held by a rubberised binder and is unable to release asbestos fiber otherwise . Only danger is where the manufacturing occurs or the material may be carelessly scrapped . I think it's a false alarm .

Not true...A minimal incease or decrease in the cylinder to head height will play a significant role in large change in Compression ratio........

Absolutely true....The air we breathe with so much of hydro carbon and Particulate materials ,are of greater concern than asbestos...

Sorry for wrong information and all confusion. By "slight",I meant very slight but leave it .... Sorry. At the same time ,I am happy that you guys are there always to correct me.