For the front the m35 should suffice.The reason why i am suggesting the m45 4.00 18 is because,while converting to mm the 4" corresponds to 101mm.The m45 4" looks a bit fat because it has a higher weight carrying capacity,and it is specifically designed for street use especially when you go over deep manholes or road undulations.Moreover if you compare the weights of the m45 and the zapper the m45 is far lighter than the mrf.I would suggest to go ahead with either the m45 or the pilot sporty,which is 100-90-18
Below is a pic of both the tyres.

My 4-valve project is not based on a laser/GF. Mine is currently a multi valve configuration that I'm developing for my RTR engine. The older head etc is no longer in existence. This one is a legal cylinder head, developed for my racing and will go into my drag chassis.
The RTR cylinder head is originally from my 165cc Drag engine which has clocked 14.8secs in a quarter. With a lot of room left to further push.
The cylinder head has some insane work and it took me months to finish and get tat level of performance. All with a 2-valve head. The cams were custom ground from USA and I crafted my own valvetrain components. So now all that has been moved into the 205cc RTR. However to support more flow for the larger engine capacity, the cyl head has been further modified and the exhaust dimensions are insane. Killer can vouch for the extra horses that we gained after I simply built a new exhaust system. Power wheelies in a 4-stroke is that, with the stock RTR gearing. The bigger carb is still a restricting factor, big time. Imagine I used to run a 29mm CV on my 165cc drag engine. The 205 is being chocked to death. So will soon shov the larger one. Like I said earlier, a few horses are yet to be unleashed with a large carb alone. The potential in that engine is immense. And FYI, we are not running too much compression either.

So this RTR205 is an extension of your drag RTR165 which i had followed and i believe that 165 was running super short stroke config with altered gear ratios to suit the quarter mile drag.So this basically is like a increased stroke version of your drag RTR.
I can only imagine how high revving the drag RTR must be.If i remember correctly that bike was running with stock RTR clutch and springs right?
So the engine-head work for the RTR 205 is pretty much done,leaving room for new piston top design ,gear ratios and fueling.Then the v-box numbers will be out shortly.

Pretty much. Well, I havent disclosed most of my engines details to anyone. So some of what you said is only true .
V-box will do the talking.

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Guys what tyre size (max width size) will fit the fiero? Is the MRF Zapper Q good? specially for mileage and durability? What size is the Fiero stock front tyre?

Fiero&Fiero F2 stock front size, similar to most other bikes is 2.75*18". I would advise you to stick to this, don't upsize the front.

Fiero rear stock size is 3.00*18" so you can upsize to 3.25*18" without any problems.
Fiero F2 rear stock size is 90/90/18" so you can upsize to 100/90*18" without any problems.
I have been using a Dunlop GeoCruiser 100/90*18" on the rear so want to revert to stock spec.this time. Zapper Q is the only tyre I found so far in 90/90/18" for my Fiero F2.
Most others are recommending the Michelin tyres. They are very good.
I say go for Michelin M45 front 2.75" &rear 3.00" if you have a Fiero.

M45 is available in 90-90-18

The website says only 3.00/3.25*18". Are you sure?

Guys my fuel tank had been leaking since a long time... the mech put some putty, but it started leaking again. So I went for a gas welding thing today. are the stickers available if I paint the tank? Guess we need to have the tank painted after a welding job. The welding guy says it will only be ready tomorrow. Guess I'll have to wait patiently. other than that, I inspected the spark plug and the center was nice and browish ... indicating good running. I will have the chain tightened when I get that tank back and give the bike a good wash. I certainly hope that spell's the end of my tank related woes.

The rear tyre is TVS 3.00", the treads are still good... front is 2.75 stock TVS. Can I use it up front? and buy a new 3.25 rear?

Front tyre needs to be rounded otherwise you will loose the front end in turns.If the rear tyre is rounded and hasn't become square,you can use it,but the speedo will be useless.Get the SUZUKI sticker done at a sticker work place.

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Bro, I guess I will have to buy new tyres ... and stick to the company specs... don't want to render the speedo useless!. But it's ok at the moment, the stock tyres are pretty tough. I got the tank back today, I hope the job has been done well and will not start leaking anytime soon. Other than that the bike is good and performs well. Just thought I might have to change the throttle cable. Do you think RTR 160 throttle cable will go with Fiero? if it does, I will go for a genuine cable as the one I got, somehow does not feel good enough.

The speedo as it is has errors,what will happen with a higher profile front tyre is ,it will make the speedo give less speed than what is and the same with distance too.That is bike would have traveled more than the shown distance on the speedo.It will be like putting a 18 inch wheel on a bike which has 17 inch front wheel.So speedo won't be useless per Se ,it might even make the speedo give more accurate numbers if it's over optimistic.
RTR throttle cable can be put on your bike.

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I think I need to change the whole throttle setup... my throttle seems to have lost it's free play and when reved and throttle let go, it takes a while for the throttle to ease back to normal position. Maybe there's some other problem... will check and see. Dirt in the carb? maybe.

Lube your throttle cable and throttle grip. Ensure it doesn't get caught in any frame routing.

gixxer_junkie_m will forward you a PM that I sent him about tyres.
I remember my Fiero F2's throttle cable snapped on Day 3. I got a free replacement then&it hasn't snapped till date. Costs Rs.121 or something.