I remember that you posted it long ago.Thanks for this idea.
I must say that is a very practical and easy fix,but my fender has damaged from the screws

I suspect you or your mechanic is doing something wrong here , possibly some tiny omission or difference in fitting the front mudguard , from stock fitting . I have pretty bad roads here too and daily hits high speed-breakers and deep new potholes hard . Never been able to break off even one of my mudguards ... be it chromed metal ones or these new plastics . They are fixed to the shocker tubes and moves with it , no way it can hit anything or deform while riding , even with severe wheel/shocker movement . Check a new vehicle's mudguard and carefully observe how it's fitted .. and if you are omitting anything .. even small . Uneven compression/expansion between the two front shocker tubes can be a cause too , or some other defect is causing it . It's unusual .

That is not a defect IMHO . That tank cap valve is NOT supposed to be an one way valve . It should be a pressure equalising valve that works both ways , but with unequal threshold pressures . a) It shall let in air to equalise the internal pressure inside the tank as the fuel is used up . b) In case the fuel vapours exceed a certain pressure threshold ( eg by expansion/vaporisation in hot sun etc ) it should then release the excess pressure and vapours out . Naturally, in such case you'd be able to smell the gas vapours so released . I've smelled it too . Fuel mileage was still 72+kmpl .
I am not sure if original splendor was fitted with an one-way equalising valve in it's tank cap . Splendor's tank cap+cover design is superb , no way of rain-water ingress into tank and looks nice too .

Passions tank cap has one way valve.
You will be amazed by the simplicity of the valve.
It is just a circular shaped plastic which seals against rubber.

I will see If I can find that old cap and upload some pictures of that valve.
(Got to search my old spareparts room)

Post edited & add Hi-Res Picture , check it again . Mine got damaged such that the screw hole part got seperated but this fix is helding it tightly .

Joy has similar tank caps as passion and believe me it hasn't been changed in this 11 years and 3 lac k ms.
@shoeb- Regarding faulty shock open the shocks fully even the inner pipes from outer pipes and wash it with kerosene and let it dry. buy new springs And the original cost some Rs 100 for one. buy two springs and refit them. Use motul(20w grade) or valvoline(15 w grade) shock oil and fill exactly 160 ml in each shock by using measuring beaker.
Use original mudguard and change the plate which mounts the fender to the shocks. It is available in spares shop and cost some Rs. 50.
You can use the caliber tacho and connect the trigger wire to the wire from pulsar coil.
Open the magnet cover and see the color code of wire going to cdi as the other wire will be grounded. then open the right panel cover and see near the indicator relay that there will be wires with male female clips. One wire will be same color as the pickup coil(most probably black wire with white line on it). connect the wire to the clips and the power wire of the tacho to the positive and negative of battery. Start the engine and see the tacho reads. Only the inner unit of tacho or the machine cost rs. 600 not the whole meter. Also you can use meter set of caliber or caliber 115 as it comes with speedo, odo, trip meter, fuel meter and rpm meter. Speedo reading will not be affected as it also runs 2.75 - 18 size tyre at front. But from my experience bajaj bikes have greater speedo error than hero honda.
@Pinaki - do not use L- wrench for engine casing bolt as it will provide too much torque and strip the threads. Instead use T- wrench and tighten it such that after tightening with freely give it a small jerk with two fingers because as the engine heats and cools it will automatically get tightened.
Where packing is used tighten it upto such extent that the packing is compressed.

Thanks Sibun'jee . will keep in mind carefully .
Today I finally found time to take out the dirty air-filter elements and put in the new set I got few days back . I had oiled the new set and kept ready in polybag since wednesday . Now I'll wash & dry the dirty set next weekend .
One thing I noticed is that the rubber boot(tube) that goes from the air filter box to the carb is coated insides with gritty dust particles . Dunno where that's coming from !!?? Certainly not from the air-filter side .. I do that very carefully always and use grease on all mating lips . May be through the gap where the crankcase breather goes in to the air-box ? Dunno , I'm totally flummoxed about this one . Any ideas guys ? That much dust will polish the bore to death in one year !

Do you remember that I posted a similar problem earlier ?
In my case it was disintegrated filter element but something else was also present there, maybe excessive oil from filter is sucked in overtime and drying??
But whatever it maybe,I think it just sticks the the boot and never enter the engine.
Proof-Both the bikes are running fine even after 8/7 yrs w/o any engine issue.(touchwood)

@pinaki- There is nothing to worry as it is with each and every bike and there is nothing to worry about. And do not open the carburettor frequently as it will decrease the life span of the carburettor.

No , I have opened the carb just once for cleaning . Once set , I don't usually open the carb anymore until it asks for service on any bike I had . There was no dust present inside this carb then . I just checked the inside of that rubber tube by chance(while putting in the air filter) with a torch light and saw the dust . Inserted finger and took out . It felt like gritty fine sand between two fingers , which alarmed me . There is no oil inside there . Bike is running fine now . There is no visible leaks in the rubber boot - tube thingy . I am planning to dismantle it and check thoroughly this weekend . Maybe replace the whole thing with new one ? It needs a cleaning anyway !

I have found a Schematic of a digital tachometer.
The basic idea and circuit has been confirmed by PSR jee.
It requires the programming of the 8bit micro controller.
If you have some free time and PIC programmer go ahead and make it.

Here is the schematic


Credits:-

PSR ji,For confirming the circuit.
Tachometer/RPM. - Jose Pino's Projects and Tidbits.

@shoeb- Yes this is a kind of tachometer used for tuning in service center. These are known as inductive tachometers and they work by picking up inductive current from the hi tension cord.
The method is correct but let me see if it will work by consulting to an electronics friend of mine.

Ok , I did it today .
Took out the side panels , seat , tank & tool-box . Put the carb choke lever on(to close the air-intake hole) . Took out the air-filter and stored in a clean poly-bag. Unscrewed the clamp on the air-boot tube on the carb-end and carefully pried it out on the air box side . Now I found a problem . The air boot tube was affixed to the hole in the air-box with some kinda rubber glue or rubber cement inside it's groove, from factory. That glue had completely given away owing to exposure to oil from the air-filter. Dunno if the dust inside the carb air-boot tube was coming from here - cause even without the adhesive , it's a pretty snug fit. Anyway I yanked out the tube , along-with the rubber flap thingy through the frame after removing the wire from the alternator that passes through a slit in that rubber flap . Washed it clean , dried and fixed it back nicely with rubber glue(dendrite) to the air-filter box hole .Fixed everything back together and the engine sounds much better now . Hopefully the fix holds .
The mysterious thin rubber tube that goes into the carb top near the idle-adjust screw , is supposed to just dangle in there on the other end, or is supposed to be connected to something . Any idea guys ??

That goes to the Air suction valve diaphragm.
Note-For some models that pipe goes to Intake manifold or the carburetor as in your case.

I am unable to get a perfect AFR on Passion+ 2005.
The engine idling rpm doesn't sound stable.
Note- my dad does not have a habit of checking or caring about mileage,the only way he reports any engine problem is by judging the pickup.
So before tuning took the bike for a spin and I checked the mileage and it was just 40kmpl. (Reserve to reserve with 1 liter)

After tuning also there is not much of a difference in mileage, idling rpm is not stable and pickup is also very low especially in 2nd gear there is a considerable amount of lag.

Planning to clean all the carburetor and all its jets.
BTW,bike's odometer has rolled over two times and it is showing ~5k(Yes,it is 205000 kms)

Findings-
1.Afr is somewhat between 2.75~3.5 turn from fully closed.
2.Engine does heat a lot.
3.There was some oil on spark plug threads.
4.Engine is not burning oil but some soot particle are coming out of exhaust when revved very hard.(No white smoke)
5.Mild Dry black sooty deposits on the inner exhaust.


History
1.Block piston changed twice @80k & 140k
2. Re bored with oversize piston 0.25 @180k
3.Clutches were replaced many times.
4.Main Bearings was changed
5.Last time clutch was replaced at 204k
6.Timing chain also replaced.

Extra rich fuel-air mixture , check the air filter if it's over-oiled,clogged with dirt, too-old-to-work etc and thereby restricting air-flow to the carb . It's an oil wet-ed foam air-filter , no ? It is possible that the carb jet's holes have worn out larger so if you do open the carb and clean , replace all the jets and the float-pin valve thingy(with black pointy rubber tip) .