[ProDigit]

19T sprocket install, "success"

So I managed to fit the 19T sprocket on the bike.
Before I expand on that, please know that your top speed lowers both in 4th and 5th gear by approx 5MPH. So it's possibly the worst gearing you can get for top speed, if you keep exhaust and intake and jettings stock.

If you plan on making your 150 clone more "cruise/travel"-friendly, this 19T is the first sprocket that makes a world of difference in terms of rideability, and feels more like the gears in your average economy vehicle or car.

Installation

The 18T sprocket with chain apparently had scraped the sprocket cover, and marked where the chain touches the cover. It's really only a small slot of about 2-3 inches wide, and about 7mm high, you need to grid off the sprocket cover, because the 19T sprocket is a bit towards the front of the cover.
On the inside of the front side of the cover (inside of the side facing the front wheel when installed), there are the 2 bolt holes, and another 2 structural lines, to reinforce the cover. These lines will be your mark lines. You grind the cover between those 2 lines, about 7mm deep, and remove the piece. It's an aluminum cover, so it should cut/saw/grind quite easily.

The stock chain with 19T will stick out of the sprocket cover only in the front. No other grinding is necessary. Unlike the 18T, where you need to grind a tiny piece on the top of the cover, on this 19T you only need to grind off the front. So if you have a 15, 16 or 17T front, and want to go to a 19T, only front side grinding is necessary.
You'll need an angle grinder (on special in harbor freight for $10), and maybe a file, to file off sharp edges. It's about a 15 minute job.


I kept the original chain, as after 200 miles, it had lengthened enough for me to install the 19T with the rear wheel all the way forward.
If you are using double nuts on your chain adjusters, you can't do that here. So, you'll need some blue Loctite on them to keep these remaining nutz in place.

The chain does rub on a metal extension on the engine block. It's nothing bad, no leaks can come from it, just a small ridge, that the chain can slowly grind down on it's own.
What I did, was I upped the idle to 2k RPM, lifted the bike's rear, and started her up, with the rear wheel spinning in 5th gear. It took about 5 minutes of idling and occasional gentle revving, for the grinding noise to go away. I then sprayed some Plastidip on the inside of the chain, to lubricate and protect the area that the chain was eating out.

I would say, the installation is mechanically speaking, fairly easy to do, without any major headaches.

Impressions 19T

I took it for a spin, and man, it feels like a normal bike now!
The gears are a lot taller. The bike usually stays within 6.5k RPM, so no more crazy vibrations.
My top speed did drop from 60MPH to about 55. I can still reach 60 in 4th but that's with the bike screaming at 8-8.5k RPM.
In 5th, the bike seems to find equilibrium at 55MPH on a flat surface.
This is probably the worst gearing if you keep the bike's intake or exhaust stock, but may be the best gearing after an intake, carburetor, and exhaust change.
I'm estimating that the bike will make more power and can push itself past 70MPH indicated (65 GPS), with an intake and exhaust tune, but we'll see.

Increasing the idle from 1500RPM (1750RPM max when hot), to 1750RPM (2k max when hot), has actually gotten rid of the low RPM bogging I got from starting from a stop in 1st gear.
No more do I need to feather the clutch as much, but can just go, even with the 19T front sprocket on.

My new setting has me riding ~45MPH at 5k RPM, and ~55MPH at 6k RPM.
The bike usually likes to hover between 55-60MPH (6-6.5k RPM) traveling alone vs tucked, or alone vs in traffic with a vehicle cutting the wind in front of me.

Future upgrades:

My next project will be installing the PZ27 carburetor with adjusted jets.
If I can't fix the top end, I'll install also an exhaust system, and pod air filter with potentially an air intake pipe.
If that doesn't increase HP, I'll have to go for a 26mm nibbi carburetor, which is slightly bigger than the PZ27, but should get more top speed out of the engine (but also is harder to idle).

Additionally, I'm still waiting for the arrival of the 30T rear sprocket, which I will install once the carburetor and air intake/exhaust is fixed, and I'll be able to install my new chain.

I've left the idea of the 20T front sprocket mod, as the 19T sprocket is already 1 size larger than the largest size that should have fitted, but with some mods, it may possibly already be too large; or, it may just be the maximum size that fits the condor. Either way, a 20T won't fit, unless you plan on grinding in the engine block and re-route the transmission wires that already have no play.