Nav75 do you know the shop or the mechanic's name for the one you visit in Goregaon?
Please let me know.

all you have is 'blocked air supply'.. Clean or replace air filters and check the connections.. See you at 100 soon.

Please dont tell me that you have done that! :-)

I would think it is the carb slide issue with your bike. As far as I know, there are members faced this issue, including me. Though I would refrain making a big talk, however, learned to live with the problem. Read the post below from Karizma Owership Thread.



PSR sir could throw more light when posted your issue again on the Ownership thread.

3750 rpm to be precise, according to the tacho.

+1
+check all these:
1. CDI connector, as you said there is some problem in start-up also.
2. Air-filter, since when are you using the same filter?

this could also happen as a result of impurities in fuel as you mentioned about rust in the tank...so maybe some part in the engine got any minor(major) damage.

Calling PSR Sir...

I changed the air filter the first thing, before any work was done on the bike. It did not help all that much.

Well, if it does around 64-66 @ 4000 rpm, then its ok, otherwise, the clutch could be an issue. Anyways, I don't think clutch is an issue, because clutch issues are more noticable than that...

Other thing you could try is tuning the carburettor. There could be 3 main adjustments: One screw which will drain fuel out of carburettor for cleaning it,
Another screw/ knob which will affect your idle rpm directly,

and the third one: This is the AFR. Tighten it full and make 3 turns towards loosening it. See if your bike starts in one crank, and also if idle rpm is maintained rock steady. If yes, keep it this way. If it doesn't start reliably or its rpm is slightly varying at idle, then further loosen it, step by step till you reach an acceptable setting.
Although, the entire tuning involves setting up the idle rpm again too, but let's leave that... First your 60 kmph problem should be solved.

--
@ PSR: Bro, awaiting your reply...

Sorry for the late reply.. Everything points towards a stuck Carburetor slide like Mr.Sriram and others pointed out..It is a known problem in ZMA . A stuck slide will not rise with Vacuum in it's ventury and restrict the top speed to 60 ~70 Kmph.
If the Thread Starter is a DIY,and technically competent person the solution is simple....loosen the carb end of the Air box hose screw, push the hose aside, and you will see the slide in the carburetor...push it up with a finger under the slide ..this will release the stuck slide, and will restore the bike to normal operation...there are many posts regarding this in the ZMA thread ,and request the TS to go through it.

@ PSR

There are no words to praise your replies your excellency...
Hats Off.

+1; and everything is open discussion

"Et Tu Nano " ?

Of course it has to be if i have to reach and help him,...and Knowledge does not belong to any single person....anyone with the inclination and hunger for it will get it....if he is humble and brave to accept his ignorance.

Thank you for the guidance regarding problematic Karizma carb

Thank you very much PSR for your pin point identification of my Karizma issue. I am a DIY type and I am going to put in all my efforts to be hands on with my bikes.

I am hopeful that I shall gain better understanding of motorcycle technology.

I appreciate your support & advice,
Dushyant

I was hoping you would have done it by now

No, he must be okay with it with an eye on the fuel prices its good to be below 60kmph

Karizma engine performance problem. Now engine performs so much better.

Hello again PSR sir.
You were absolutely spot on with what was causing the fueling issue with my Karizma's mid and top end.
However, as I tried to get my hands dirty to resolve it myself, I realised that quite a few screws and fasteners on the bodywork and the carb were jammed. I got them opened up at the friendly mechanic's shop. The A/F screw had to be drilled out and replaced. The slide, as you rightly pointed out was not free to reciprocate inside the carb. When the carb was opened up, turns out the spring loading the diaphragm was bent and consequently allowed the throttle slide to open up to approximately 40% of it's stroke. Not surprisingly the bike was performing to only 40% of the available engine performance. Simply re-seating the spring correctly immediately smoothened the stroke of the throttle slide. Now the bike runs like when it was new.
The next aspect of the project now is to get rid of the rust around the fuel filler cap so that the rust & water does not collect inside the fuel tank.

I genuinely appreciate your astute insight into such technical problems.

Thanks,
Dushyant

Wow! I have nothing to do here, but was just going through looking for how the TS managed to solve the problem. The manner in which PSR hit bull's eye first post is amazing! Kudos to you Sir!!