My serious advise to you buddy,if your mech says that the head enlargement has lead to oil entering the combustion chamber,then seriously it's high time you started searching for a different mech!!
We(me,psr and vignesh) have been telling you from a long time as to what could be the problem.

The valvetrain components might be at fault,due to lugging being done when the alternator was being run.

Running with low oil will first ruin the bore,crank bearings and connecting rod itself along with the crank shaft.Then the head components.So if cam and rockers are a goner,i very much doubt whether the bore/piston will be ok.
Then it's a good idea that you go for a used RTR head itself,because the cost of getting the parts will be same as that of a used head with all the parts in it.
Get the re-bore done to .5mm(hopefully) otherwise with low oil levels a bore wears out very quickly and it might need 1mm oversize.

@rafting guru

The cam your mech has bought is a chinese one.With it,the bike will never perform properly and it will wear out drastically.

@Vignesh

Good going with the FFE.The engine's getting flooded i think and that's why the plug's getting ruined,because from the looks of it,they are nice and dark.While you're saying that the engine's compression is very high and that the engine boils over when run at high revs.All these should mean the plugs should be very light in color.Or,you haven't done the plug chop properly.

@Sarvajit

Good going bro.No need to thank us.

57mm to 62.5mm over-bore without need for a re-sleeve??That's not possible.

The mech never said that enlargement of the head has caused all these problems...
see, the re-bore definitely needs to be done and i am not happy with the head enlargement as its causing a lot of knocking...
I am looking out for a used rtr's head from almost a year, but haven't found one yet.

something tells me that only a new head will sort out the oil drinking problems, because when the bore and piston were alright, it still drank a lot of oil.
i want to re-bore but the mech says that +1 sized pistons aren't available for rtr 180.
So i was thinking to plonk a 63.5mm cbz's piston after re-bore as per vignesh's suggestion and plonk an rtr 180's head.
But i can't find a used rtr 180's head.
So should i buy a brank new rtr's head and plonk it with the +1 sized (CBZ's) piston after rebore, or shall i consider changing the cam and stuff and run the same head ??

Don't go around looking for 180's head in particular.Try to find a RTR160's head ,that should do just as fine.Then, if a re-bore is needed,just go for the next size piston.The lathe guys would have em.
Buying a brand new RTR head is meaningless ,if you'd ask me.It used to cost somewhere in the line of 5 to 6k a few years ago,when a bore kit used to cost 2.2k.So now it would have gone up as well.

I might keep looking as long as i can, and will do the needful.
Thinking of putting up an extra pressure plate in the clutch as well, to avoid slippage...

Thanks a lot...

Update :-

Just got a call from my mech, he has sourced a +1 oversized piston and was suggesting that i run with a new cam + rocker arms + valves seals and use the same head after some polishing...

was asking for a confirmation, shall i go ahead, and later see if something isn't well ??

Sure,no harm in it.But make sure the cam is original one.That's why,if my engine's cam goes,i'll then go for a used rtr head itself.

exactly.

Even i thought that when my cam will die, I'd go for a used RTR head...
But the damm thing isn't available here......

Head enlargement is never a process that has to be considered skeptical.. It is a very common thing thats been done for years..

+1
ALTERNATOR??

Not really necessary to get the RTR head unless you are using the bike for race purposes.. Stock fiero head is really good.. get the apache 150 cam shaft and rockers.. Now you have rollers to follow the cam..

Its really not wise to compromise on engine components... Might create a headache and spoil the love towards our bike..

Yeah.. Its been running rich since my pilot jet was damaged.. i found it out accidentally while cleaning the carb.. Maybe thats the reason why my plugs never lasted long.. Now i have changed the jet and the plug color has become more pale.. Performance seems to be the same on road.. Have to test on the dirt..
Bro, i have done it on a fiero about an year ago and that bike has done 15k+, yet still running great.. Actually it is running 62.25 mm(first oversize of rtr160).. i prefer the Suzuki fiero stock cylinder for street purposes because it is an aluminium block which is a better conductor of heat.. Its even smoother than RTR cylinder..
Knocking has no reason to go with head enlargement.. Engine knock possibilities are:
1. Valve hitting the piston(might cause serious knocking when engine heats up)..
2. Valve guide clearance not set properly.
3. Crank big end has worn out(shake in con rod and engine knocks when throttle is flicked when in idle and stalls)
4. Octane content on fuel is low or when compression is very high(i use only premium)..
5. Timing chain and/or tensioner pad wear..
6. Defective gear wheels(Rarely happens on a fiero )..

If head enlargement is done properly, none of these will occur..
The valve oil seal is the only possible way through which oil may enter the combustion chamber.. Valve oil seal gets badly damaged if valve is bent..

Many changes has to be made to the piston.. If not done properly, the piston will hit the head and cause serious damage... if done properly, it will last a lifetime..you'll love its low end power.. Also make sure to build some calf muscles if you don't have self start..
I guess rtr 160 and 180 have the same head.. only the intake manifold is different.. I'll refer the part number...
Thats a clutch eater.. Clutch responds well, but your plates won't last even 10-15 k or even less since this is very addictive(you know what i mean.. )

@ vignesh

As far as the alternator thing is concerned, i think you should have a look at this ---> http://www.xbhp.com/talkies/desi-bik...st-indian.html

Besides, i have been facing knocking issues from the beginning, i have to ease out the clutch in almost every gear as we do in the 1st to avoid knocking.
Even in roll on the knocking takes place if a sudden wack is made.
All this things work until the clutch is alright, but after weeks the clutch starts slipping and does the ease out work for me.

Knocking only and only occurs at lower rpms.
However all the related problems were taken care of, and now its reduced after the head enlargement, but its still there somewhere...

@ all

Talking about the cam, which cam should i go for ?
rtr 160/180 ?
Apache 150 ?
fiero orignal cam ?

If possible, let me know about the cost of the above too...

Do you mean to say that the fiero bore is running without a cast iron sleeve?because the stock fiero/f2/fx/apache(almost all the bikes in the world) sleeve isn't thick enough to be bored out to take a 62.5mm(5.5mm over-bore on the stock sleeve) piston.That's because if the sleeve is made too thick then the heat will become too much and engine life will go down.Conversely if the sleeve is bored out to the max,then it will warp when engine gets heated and this once again will lead to loss in compression.So there will be a balance made as to the thickness of a cast iron sleeve in a aluminium block.

No,what i mean't is,since you're using a rx carb and not a cv carb,your engine might be getting flooded once in a while on start up.That's the main spark plug killer,the engine will start up eventually(if compression is high),but the performance will never be there.That's why i have been saying a iridium plug will perform much much better when faced with such situations.From my experience ,iridium plug is the only one which has no problem with flooding.It's performance in comparison to conventional plug is very clear and can be felt with ease.
The black color is the preferred color,it will ensure engine won't heat up on higher revs.

Coming to the apache intake manifolds,yes the RTR180 has a wider one ,at the entrance of the manifold that is,then it narrows to the same width as that of the RTR160.This difference was brought to my notice by psr and i've been using it since then.It does make a difference.

Yes cbz piston to be installed on nanotech's bike will need some knowledgeable lathe guys.
Like vignesh has said,go for the apache 150 cam and rockers.I haven't done it so i wouldn't know about it.But it will increase engine refinement and bring the torque lower down the rev range.That's because of cam.This can be felt as the snap! kinda pick-up felt when using apache/RTR heads.

Mother of MODS!!!

@gixxer
the resulting sleeve was quite thin.. But still the performance is still good even after 15k odd kms.. Its was a 62.25 mm piston...

I know a fiero running with 68.5 mm piston on stock rtr sleeve.. What you are saying is 100 % true about heat transfer.. But it has been done and running great bro..

Regarding the plug,maybe i should give the iridium plug a try.. How much wud it cost??

@ vignesh

Don't forget to see the beam shots at page 5...

@ gix

its apache 150's cam then...
Will buy one tomorrow itself and do the needful...