If you suspect an air leak, you should do a leak-down test.

Here are couple of links that I found from Google:

Pressure Testing Two Stroke Engines

Why do you say that you don't have any way of checking compression? You just need to buy (or borrow) a compression gauge. It will cost around 650 bucks.

Hope you are able to find the problem.
cheers!
Rohit.

Recommended is NGK with 5 or 6 grade plugs(BP5ES or 6ES)...Do not use resistor plugs,and check plug cap for bad connection or break inside..by changing with new plug cap.
Hope you had fitted the Rotary Disk Valve in correct orientation.

I am now re-painting/rebuilding my KB for RTO inspection next week..She will be completing 25 yrs with me..

do you own a compression gauge

Yes I do. I think its a Taiwan make.

My 25 year old KB100 recently re-painted by me (personally) for RC renewal.

These clean lines in the bike are always a pleasure to look at PSR sir..! Any specific reasons for this color paint job?

O.T: Was watching "Agni Natchathiram" movie last night and saw a scene were Prabhu comes to Arrest Karthik whose been hanging out with his friends where there are a whole lot of bikes parked & saw brand new Rx 100, KB-100, AX-100 & a few others & the clean lines they've got was simply amazing to look at.. Wish we get back those bikes again...

@PSR sir, I was amazed when happened to know that you had done the paint job all by yourself. It was such a clean job that hardly could make out that it was carried on at your door front.

psr sir though the paint job looks good , gotta say this painting on plated parts and spokes was a very bad idea , ditto for the engine covers and wheel hubs , there was a sort of charm in the chrome

I am fond of Lavender and so painted the tank and shields to this color,...ten years back..Only the head,mud guards,spokes,and crank side covers were painted by me now..

Yeah I even surprised myself and others in my family..they did not expect this finish...just some patience and perseverance..three days of 3 hrs each day was enough to do this job...
The wheel hubs ,fork legs,crank side case covers,chain cover, all come with Aluminum painting OE, so I had not done anything otherwise. Only the spokes which are supposed to be Chrome Plated was painted, as also the front Mud guard.The shock absorbers too came painted ,...though with Silver cap and black springs..(look up the Pic in the Service Manual)
I woke up to the fact that I had only 6 days for FC,,with a sat and sunday included....so went for the painting the parts which is a quick fix .
I learnt later that for each default year of FC not done the fine/penalty is Rs.60/- per year . Had I known this I would have taken the time to do the chrome parts also properly, ....though the RTO inspector said that the bike is very well kept and cared for and signed documents without any fuzz.( Vitamin M was doing the work)

60/- per year only ,and yet ..... you should know that here in kerala we get fined about 2.5k for missing the retest

Oh my GOD 2.5 K .....In fact after hearing from the person ,who was taking care of the whole thing,I went to RTO and saw the list of charges on the board, and was shocked to see the penalty/fine charges for RC renewal was Rs.60/- per every year... the whole thing including, Green tax, pollution approval, regular renewal,surcharge ,cess,and inspection charges is approx Rs1,000/-.(Other charges extra ) I think you should visit RTO and see the board kept outside for information to public regarding various charges.

Rebuild Update

So, after assembling everything, the bike refused to start. Frantic calls to my mentors, tons of research over the internet, lots of fretting and fuming....and finally I gave in to some sane advice and called a mechanic home to have a look.

He couldn't figure out what was wrong so I had to take the bike to his shop.

The first thing he checks - alignment of piston rings and that's all wrong. Now I did check that while installing those but apparently while pressing the rings to push the piston into the block, they might have become misaligned.

The next thing he did was to change the magneto coil plate. Fortunately I had a spare one with me. I'm not convinced that there was anything wrong with it but anyway - what works should be good and what doesn't needs to be changed.

The final thing that he did - check the alignment of the rotary disc valve. It was apparently wrong. Now this too was checked by me but apparently my understanding was not correct.

The bike started on the first kick after that and I rode it back to my house. There are still a zillion things to do yet I'm so relieved just to hear the engine revv.

I'm a little disappointed though, that after doing everything myself, I had to employ a mechanic to get the bike to fire. But I have only my overconfidence to blame. Had I listened to the advice of PSR Anna, Muthu Anna, Yamdoot and Sarin, I could have done everything by myself. Really silly of me.

And then, I'm again reminded of PSR Anna's signature - 'When was the last time you did something for the first time?'

Meanwhile, a big Thanks to Yamdoot for sending me some really vital and rare to find OEM spares.

a very big thanks to you for not loosing faith and continuing the work , most of all for for making my thread worth it

Suggestions for a leg guard

hey, let's take our mutual admiration club somewhere else or we'll keep embarrassing each other.

as i said earlier, there are a zillion things to do on the bike. foremost on the 'to do list' is to fix a suitable leg guard. now, the KB leg guards are hard to find. i was thinking of the single rod type that you get to see on a few bikes; but i am given to understand that these aren't too safe in case the bike meets with an accident.

which leg guard would look good on my bike? suggestions invited.

Hey rookie! Long time! You could get the in-line 3 bar guard if it is available. Not the one that wraps around but the one with a big bar at the top then a smaller one and then the smallest one.....hope I'm not sounding like an idiot. Is the bike starting now?